Posters : 39
Posters : 39
39. Tailoring Si Nanocone Arrays via Simultaneous Low Energy Helium Ion Sputtering on Metal and Si Surfaces
39. Tailoring Si Nanocone Arrays via Simultaneous Low Energy Helium Ion Sputtering on Metal and Si Surfaces
N. Termini, J. K. Tripathi, A. Hassanein
N. Termini, J. K. Tripathi, A. Hassanein
25th Conference on the Application of Accelerators in Research and Industry (CAARI-2018); Grapevine, Texas, USA
25th Conference on the Application of Accelerators in Research and Industry (CAARI-2018); Grapevine, Texas, USA
August 12-17, 2018
August 12-17, 2018
38. Tuning MoO3 nanostructures using low energy high flux He+ ion irradiation
38. Tuning MoO3 nanostructures using low energy high flux He+ ion irradiation
J. K. Tripathi, T. J. Novakowski, A. Sundaram, A. Q. Damico, and A. Hassanein
J. K. Tripathi, T. J. Novakowski, A. Sundaram, A. Q. Damico, and A. Hassanein
Materials Science & Technology 2017 (MS&T 17); Pittsburgh, Pennsylvania, USA
Materials Science & Technology 2017 (MS&T 17); Pittsburgh, Pennsylvania, USA
Oct. 8-12, 2017
Oct. 8-12, 2017
37. Effect of D+ ion irradiation on Ta under fusion-relevant conditions
37. Effect of D+ ion irradiation on Ta under fusion-relevant conditions
T. J. Novakowski, J. K. Tripathi, and A. Hassanein
T. J. Novakowski, J. K. Tripathi, and A. Hassanein
Materials Science & Technology 2017 (MS&T 17), Pittsburgh, Pennsylvania, USA
Materials Science & Technology 2017 (MS&T 17), Pittsburgh, Pennsylvania, USA
October 08 -12, 2017
October 08 -12, 2017
36. Emission dynamics of tungsten fuzz in response to ELM-like heat loading
36. Emission dynamics of tungsten fuzz in response to ELM-like heat loading
G. Sinclair, J. K. Tripathi, P. K. Diwakar, E. J. Wallace, and A. Hassanein
G. Sinclair, J. K. Tripathi, P. K. Diwakar, E. J. Wallace, and A. Hassanein
16th International Conference on Plasma-Facing Materials and Components for Fusion Applications (PFMC-16), Neuss near Düsseldorf, Germany
16th International Conference on Plasma-Facing Materials and Components for Fusion Applications (PFMC-16), Neuss near Düsseldorf, Germany
May 16 -19, 2017.
May 16 -19, 2017.
35.Temperature- and Fluence- Dependent Surface Morphology Evolution of Ta under High Flux, Low Energy He+ Ion Irradiation
35.Temperature- and Fluence- Dependent Surface Morphology Evolution of Ta under High Flux, Low Energy He+ Ion Irradiation
Theodore Novakowski, Jitendra Tripathi, Ahmed Hassanein
Theodore Novakowski, Jitendra Tripathi, Ahmed Hassanein
2016 MRS Fall Meeting & Exhibit, Boston, Massachusetts
2016 MRS Fall Meeting & Exhibit, Boston, Massachusetts
November 27 –December 2, 2016
November 27 –December 2, 2016
34. Tailoring W2O3 nanostructures using low energy high flux He+ ion irradiation
34. Tailoring W2O3 nanostructures using low energy high flux He+ ion irradiation
J. K. Tripathi, T. J. Novakowski, J. Fiala, A. Sundaeram, and A. Hassanein
J. K. Tripathi, T. J. Novakowski, J. Fiala, A. Sundaeram, and A. Hassanein
Materials Science & Technology 2016 (MS&T 16), Salt Lake City, UT, USA
Materials Science & Technology 2016 (MS&T 16), Salt Lake City, UT, USA
October 23-27, 2016.
October 23-27, 2016.
33. Tuning Si nanostructures by low-energy high flux He+ ion irradiation
33. Tuning Si nanostructures by low-energy high flux He+ ion irradiation
T. J. Novakowski, J. K. Tripathi, and A. Hassanein
T. J. Novakowski, J. K. Tripathi, and A. Hassanein
Materials Science & Technology 2016 (MS&T 16), Salt Lake City, UT, USA
Materials Science & Technology 2016 (MS&T 16), Salt Lake City, UT, USA
October 23-27, 2016.
October 23-27, 2016.
32. Effect of Dual Ion Beam Irradiation (Helium and Deuterium) on Tungsten-Tantalum Alloys under Fusion Relevant Conditions
32. Effect of Dual Ion Beam Irradiation (Helium and Deuterium) on Tungsten-Tantalum Alloys under Fusion Relevant Conditions
S. Gonderman, J. K. Tripathi, T. J. Novakowski, and A. Hassanein
S. Gonderman, J. K. Tripathi, T. J. Novakowski, and A. Hassanein
22nd International Conference Plasma Surface Interactions in Controlled Fusion Devices (22nd PSI); Rome, Italy
22nd International Conference Plasma Surface Interactions in Controlled Fusion Devices (22nd PSI); Rome, Italy
May 30- June 3, 2016.
May 30- June 3, 2016.
31. Thermal and Structural Evolutions of Tungsten Surface Exposed to Low-Energy Helium Ion Irradiation, by Transient Heat Loading
31. Thermal and Structural Evolutions of Tungsten Surface Exposed to Low-Energy Helium Ion Irradiation, by Transient Heat Loading
G. Sinclair, J. K. Tripathi, P. K. Diwakar, J. Linke and A. Hassanein;
G. Sinclair, J. K. Tripathi, P. K. Diwakar, J. Linke and A. Hassanein;
22nd International Conference Plasma Surface Interactions in Controlled Fusion Devices (22nd PSI); Rome, Italy
22nd International Conference Plasma Surface Interactions in Controlled Fusion Devices (22nd PSI); Rome, Italy
May 30- June 3, 2016.
May 30- June 3, 2016.
30. Tailoring Molybdenum Fiber-Form Nanostructures (Mo-Fuzz) Using Carbon Impurity Under Helium Ion Irradiation in Extreme Conditions
30. Tailoring Molybdenum Fiber-Form Nanostructures (Mo-Fuzz) Using Carbon Impurity Under Helium Ion Irradiation in Extreme Conditions
N. Bharadwaj, J.K. Tripathi, S. Gonderman, and A. Hassanein
N. Bharadwaj, J.K. Tripathi, S. Gonderman, and A. Hassanein
Undergraduate Research & Poster Symposium, Purdue Memorial Union North & South Ballrooms, Purdue University, USA
Undergraduate Research & Poster Symposium, Purdue Memorial Union North & South Ballrooms, Purdue University, USA
April 12, 2016
April 12, 2016
The performance of plasma facing components (PFC) is of great important for the realization of prototype nuclear fusion. Tungsten (W) has been considered as the leading high-Z PFC material for these reactors and tokamaks due to its superior thermos-physical properties, high melting point, low sputtering yield, and low tritium inventory. However, its surface deteriorates significantly under helium ion (He+) irradiation in extreme (fusion) conditions and forms nanoscopic fiber like structures (fuzz). Formation of fuzz nanostructure on W can be suppressed by the presence of plasma impurities such as carbon (C) and beryllium. We present, the effects of C impurity on molybdenum (Mo) fuzz evolution due to He+ ion irradiation. For mixing the C impurity on Mo surface, a mixture of helium and methane gas has been used. Separate experiments with 100% pure He+ and with mixture gas have been performed. Ion energy (100eV), ion-flux (7.2 x 1020 ions m-2 s-1), ion-fluence (2.6 x 1024 ions m-2) and target temperatures (923 K) were chosen from our previous studies and fixed constant throughout the study. Post irradiation, surface modification and compositional analysis, were studied using scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Optical-reflectivity measurements were also performed for monitoring the surface deteriorations occurred due to ion irradiations. Our results indicate that 0.5 % C impurity may prevent almost all the Mo fuzz formation. Since fuzz evolution in PFCs (viz. W and Mo) is a very serious concern for all the tokamaks including ITER; the study has significant relevance in fusion applications..
The performance of plasma facing components (PFC) is of great important for the realization of prototype nuclear fusion. Tungsten (W) has been considered as the leading high-Z PFC material for these reactors and tokamaks due to its superior thermos-physical properties, high melting point, low sputtering yield, and low tritium inventory. However, its surface deteriorates significantly under helium ion (He+) irradiation in extreme (fusion) conditions and forms nanoscopic fiber like structures (fuzz). Formation of fuzz nanostructure on W can be suppressed by the presence of plasma impurities such as carbon (C) and beryllium. We present, the effects of C impurity on molybdenum (Mo) fuzz evolution due to He+ ion irradiation. For mixing the C impurity on Mo surface, a mixture of helium and methane gas has been used. Separate experiments with 100% pure He+ and with mixture gas have been performed. Ion energy (100eV), ion-flux (7.2 x 1020 ions m-2 s-1), ion-fluence (2.6 x 1024 ions m-2) and target temperatures (923 K) were chosen from our previous studies and fixed constant throughout the study. Post irradiation, surface modification and compositional analysis, were studied using scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Optical-reflectivity measurements were also performed for monitoring the surface deteriorations occurred due to ion irradiations. Our results indicate that 0.5 % C impurity may prevent almost all the Mo fuzz formation. Since fuzz evolution in PFCs (viz. W and Mo) is a very serious concern for all the tokamaks including ITER; the study has significant relevance in fusion applications..
29. Effect of Carbon Impurity on Molybdenum Nanostructure evolution under Helium Ion Irradiation in Extreme Conditions
29. Effect of Carbon Impurity on Molybdenum Nanostructure evolution under Helium Ion Irradiation in Extreme Conditions
The Summer Undergraduate Research Fellowship (SURF) Symposium 6 August 2015 Purdue University, West Lafayette, Indiana, USA
The Summer Undergraduate Research Fellowship (SURF) Symposium 6 August 2015 Purdue University, West Lafayette, Indiana, USA
The performance of plasma facing components (PFC) is of great important for the realization of prototype nuclear fusion. Tungsten has been considered as the leading high-Z PFC material for these reactors and tokamaks due to its superior thermophysical properties, high melting point, low sputtering yield, and low tritium inventory. However, its surface deteriorates significantly under helium ion irradiation in extreme (fusion) conditions and forms nanoscopic fiber like structures (fuzz) Recent studies show that the formation of fuzz nanostructure on tungsten can be suppressed by the presence of plasma impurities such as carbon and beryllium. In the present study, the effects of carbon impurity on molybdenum nanostructure evolution under extreme condition helium ion irradiation have been investigated. For mixing the carbon impurity on molybdenum surface, a mixture of helium and methane (CH4) gas has been used. Separate experiments with 100% pure helium and with mixture gas have been performed. Ion energy (100eV), ion-flux (7.2 × 1020 ions m-2 s -1), ion-fluence (2.6 × 1024 ions m-2) and target temperatures (923K) were chosen from our previous studies and fixed constant during the whole study, for all the samples. The surface modification and compositional analysis, due to 100% pure helium ion and “helium+ carbon” ion irradiations, will be studied using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), respectively. In addition, optical-reflectivity measurements will also be performed for monitoring the surface deterioration due to energetic pure helium ion and mixture “helium+carbon” ion irradiations. Our results indicate that 0.5 % carbon impurity (a mixture of 97.5 % helium and 2.5% methane gas) may prevent almost all the molybdenum fuzz formation and deposit a thin carbon layer on molybdenum surface.
The performance of plasma facing components (PFC) is of great important for the realization of prototype nuclear fusion. Tungsten has been considered as the leading high-Z PFC material for these reactors and tokamaks due to its superior thermophysical properties, high melting point, low sputtering yield, and low tritium inventory. However, its surface deteriorates significantly under helium ion irradiation in extreme (fusion) conditions and forms nanoscopic fiber like structures (fuzz) Recent studies show that the formation of fuzz nanostructure on tungsten can be suppressed by the presence of plasma impurities such as carbon and beryllium. In the present study, the effects of carbon impurity on molybdenum nanostructure evolution under extreme condition helium ion irradiation have been investigated. For mixing the carbon impurity on molybdenum surface, a mixture of helium and methane (CH4) gas has been used. Separate experiments with 100% pure helium and with mixture gas have been performed. Ion energy (100eV), ion-flux (7.2 × 1020 ions m-2 s -1), ion-fluence (2.6 × 1024 ions m-2) and target temperatures (923K) were chosen from our previous studies and fixed constant during the whole study, for all the samples. The surface modification and compositional analysis, due to 100% pure helium ion and “helium+ carbon” ion irradiations, will be studied using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), respectively. In addition, optical-reflectivity measurements will also be performed for monitoring the surface deterioration due to energetic pure helium ion and mixture “helium+carbon” ion irradiations. Our results indicate that 0.5 % carbon impurity (a mixture of 97.5 % helium and 2.5% methane gas) may prevent almost all the molybdenum fuzz formation and deposit a thin carbon layer on molybdenum surface.
28. Effect of Helium Ions Energy on Molybdenum Surfaces Under Extreme Conditions
28. Effect of Helium Ions Energy on Molybdenum Surfaces Under Extreme Conditions
The Summer Undergraduate Research Fellowship (SURF) Symposium 6 August 2015 Purdue University, West Lafayette, Indiana, USA
The Summer Undergraduate Research Fellowship (SURF) Symposium 6 August 2015 Purdue University, West Lafayette, Indiana, USA
Plasma facing components (PFCs) in fusion devices must be able to withstand high temperatures and erosion due to incident energetic ion radiations. Tungsten has become the material of choice for PFCs due to its high strength, thermal conductivity, and low erosion rate. However, its surface deteriorates significantly under helium ion irradiation in fusion-like conditions and forms nanoscopic fiber-like structures, or fuzz. Fuzz is brittle in nature and has relatively lower thermal conductivity than that of the bulk material. Small amounts of fuzz may lead to excessive contamination of the plasma, preventing the fusion reaction from taking place. Despite recent efforts, the physical mechanism of the surface deterioration is still not clear. This necessitates finding alternative materials for PFCs. In this report, the effect of helium ion energy on molybdenum surfaces is investigated. Helium ion irradiations on mirror finished polished molybdenum samples are performed as a function of helium ion energy from 100-1600eV with fixed values of ion-flux (7.2 × 1020 ions m-2 s -1), ion-fluence (2.6 × 1024 ions m-2), and temperature (923K). The surface modifications were studied using scanning electron and atomic force microscopy along with X-ray photoelectron spectroscopy and optical-reflectivity measurements. Reduction in the “protrusion” of fuzz from the surface and fuzz density at increased energy have been seen from microscopy and optical reflectivity studies. These findings further the understanding of fuzz formation on high-Z refractory metals for fusion applications.
Plasma facing components (PFCs) in fusion devices must be able to withstand high temperatures and erosion due to incident energetic ion radiations. Tungsten has become the material of choice for PFCs due to its high strength, thermal conductivity, and low erosion rate. However, its surface deteriorates significantly under helium ion irradiation in fusion-like conditions and forms nanoscopic fiber-like structures, or fuzz. Fuzz is brittle in nature and has relatively lower thermal conductivity than that of the bulk material. Small amounts of fuzz may lead to excessive contamination of the plasma, preventing the fusion reaction from taking place. Despite recent efforts, the physical mechanism of the surface deterioration is still not clear. This necessitates finding alternative materials for PFCs. In this report, the effect of helium ion energy on molybdenum surfaces is investigated. Helium ion irradiations on mirror finished polished molybdenum samples are performed as a function of helium ion energy from 100-1600eV with fixed values of ion-flux (7.2 × 1020 ions m-2 s -1), ion-fluence (2.6 × 1024 ions m-2), and temperature (923K). The surface modifications were studied using scanning electron and atomic force microscopy along with X-ray photoelectron spectroscopy and optical-reflectivity measurements. Reduction in the “protrusion” of fuzz from the surface and fuzz density at increased energy have been seen from microscopy and optical reflectivity studies. These findings further the understanding of fuzz formation on high-Z refractory metals for fusion applications.
27. Response of Tungsten Materials using Dual Ion Beam Irradiation (Helium and Deuterium) in the Presence of ELM-like Transient Heat Loads
27. Response of Tungsten Materials using Dual Ion Beam Irradiation (Helium and Deuterium) in the Presence of ELM-like Transient Heat Loads
Currently, tungsten remains the prime candidate material for plasma facing components (PFCs) for future fusion devices because of its high melting point, low erosion, and strong mechanical properties [1]. However, continued investigation has shown tungsten to undergo severe morphology changes under fusion-like conditions [2, 3]. In addition to surface morphology changes, the retention properties of tungsten are subject to change when exposed to helium and/or deuterium ion irradiations. In this regard, recent results revealed a reduction in the retention properties of tungsten due to the exposer of deuterium-helium plasma mixtures [4], suggesting synergistic effects between the irradiation species, which need further investigation.
Currently, tungsten remains the prime candidate material for plasma facing components (PFCs) for future fusion devices because of its high melting point, low erosion, and strong mechanical properties [1]. However, continued investigation has shown tungsten to undergo severe morphology changes under fusion-like conditions [2, 3]. In addition to surface morphology changes, the retention properties of tungsten are subject to change when exposed to helium and/or deuterium ion irradiations. In this regard, recent results revealed a reduction in the retention properties of tungsten due to the exposer of deuterium-helium plasma mixtures [4], suggesting synergistic effects between the irradiation species, which need further investigation.
The objective of this work is to investigate several different tungsten materials when exposed to helium and deuterium ion beam irradiations while simultaneously being exposed to ELM-like transient heat loads. This study will allow for deeper understanding of the synergistic effects induced by multiple ion irradiation species on tungsten surface morphology changes and its retention properties. These properties will also be compared when the various tungsten samples are subjected to transient heat loads simulated by the use of pulsed laser irradiations. The tungsten targets are irradiated by 100 eV helium and/or dueterium ions using 1.2 x 1021 ion m-2 s-1 ion flux, and with a simultanious transient heat load application using a long pulse NdYAG laser with power density up to several GW/m2, at different target temperatures in the range of 773- 1223K. Post irradiation characterizations are performed using field-emission scanning electron microscopy (FE-SEM) to study the morphology evolution and thermal desorption spectroscopy (TDS) to reveal the retention properties. Additionaly optical-reflectvity and focused ion beam (FIB) analysis are used to provide surface deterioration and depth information on the resultant morphology.
The objective of this work is to investigate several different tungsten materials when exposed to helium and deuterium ion beam irradiations while simultaneously being exposed to ELM-like transient heat loads. This study will allow for deeper understanding of the synergistic effects induced by multiple ion irradiation species on tungsten surface morphology changes and its retention properties. These properties will also be compared when the various tungsten samples are subjected to transient heat loads simulated by the use of pulsed laser irradiations. The tungsten targets are irradiated by 100 eV helium and/or dueterium ions using 1.2 x 1021 ion m-2 s-1 ion flux, and with a simultanious transient heat load application using a long pulse NdYAG laser with power density up to several GW/m2, at different target temperatures in the range of 773- 1223K. Post irradiation characterizations are performed using field-emission scanning electron microscopy (FE-SEM) to study the morphology evolution and thermal desorption spectroscopy (TDS) to reveal the retention properties. Additionaly optical-reflectvity and focused ion beam (FIB) analysis are used to provide surface deterioration and depth information on the resultant morphology.
References:
References:
[1] J.W. Davis, VR Barabash, A Makhankov, et al., J. Nucl. Mater., 258 (1998)
[1] J.W. Davis, VR Barabash, A Makhankov, et al., J. Nucl. Mater., 258 (1998)
[2] D. Nishijima , MY Ye, N Ohno and S Takamura, J. Nucl. Mater., 329 (2004)
[2] D. Nishijima , MY Ye, N Ohno and S Takamura, J. Nucl. Mater., 329 (2004)
[3] S. Kajita, W Sakaguchi, N Ohno, et al., Nucl. Fusion 49 (2009)
[3] S. Kajita, W Sakaguchi, N Ohno, et al., Nucl. Fusion 49 (2009)
[4] M. Miyamoto et al. Nuclear Fusion 49.6 (2009): 065035.
[4] M. Miyamoto et al. Nuclear Fusion 49.6 (2009): 065035.
26. Fluence-Dependent Surface Modification of Niobium by Low Energy He+ Ion Irradiation at Elevated Temperatures
26. Fluence-Dependent Surface Modification of Niobium by Low Energy He+ Ion Irradiation at Elevated Temperatures
The present study aims to elucidate fluence thresholds for observed nano-scale tendrile- (fuzz) like surface structures in Niobium resulting from low-energy, high-flux He+ ion irradiation. Mirror finished polished Nb samples were irradiated at normal incidence with 100 eV He+ ions using 1.2 x 1020 ions m-2 s-1 flux as a fuction ion fluence up to 1.6 x 1025 ions m-2. The study has been performed at several target temperatures in the range 773 to 1223 K. The resulting surface morphology and chemical compositions were monitored using field-emission scanning electron (FE-SEM) and atomic force (AFM) -microscoy and X-ray photoelectron spectroscopy (XPS), respectively. Additionally, optical reflectivity and thermal desorption spectroscopy (TDS) measurements were also performed for putting further insight into possible physical driving mechanisms of surface deformation and structure formation.
The present study aims to elucidate fluence thresholds for observed nano-scale tendrile- (fuzz) like surface structures in Niobium resulting from low-energy, high-flux He+ ion irradiation. Mirror finished polished Nb samples were irradiated at normal incidence with 100 eV He+ ions using 1.2 x 1020 ions m-2 s-1 flux as a fuction ion fluence up to 1.6 x 1025 ions m-2. The study has been performed at several target temperatures in the range 773 to 1223 K. The resulting surface morphology and chemical compositions were monitored using field-emission scanning electron (FE-SEM) and atomic force (AFM) -microscoy and X-ray photoelectron spectroscopy (XPS), respectively. Additionally, optical reflectivity and thermal desorption spectroscopy (TDS) measurements were also performed for putting further insight into possible physical driving mechanisms of surface deformation and structure formation.
25. Properties of Tungsten-Tantalum alloys after He Ion Beam and Irradiation
25. Properties of Tungsten-Tantalum alloys after He Ion Beam and Irradiation
Currently, tungsten remains the prime candidate material for plasma facing components (PFCs) for future fusion devices because of its high melting point, low erosion, and strong mechanical properties. However, continued investigation has shown tungsten to undergo severe morphology changes under fusion-like conditions. In this work we investigates several different tungsten-tantalum alloy materials when exposed to helium ion beam irradiation. The targets are irradiated with 100 eV helium ions at different temperatures (773-1223K) using 1.2 x 1021 ion m-2 s-1 ion flux. Post irradiation characterizations are performed using field-emission scanning electron microscopy (FE-SEM) to study the morphology evolution, optical-reflectivity for monitoring surface deterioration, X-ray photoelectron spectroscopy (XPS) to verify alloy concentrations, and X-ray diffraction (XRD) to analyze crystallographic changes in the samples due to alloying. Future work is discussed about the use of thermal desorption spectroscopy (TDS) to investigate the retention properties of tungsten-tantalum alloys.
Currently, tungsten remains the prime candidate material for plasma facing components (PFCs) for future fusion devices because of its high melting point, low erosion, and strong mechanical properties. However, continued investigation has shown tungsten to undergo severe morphology changes under fusion-like conditions. In this work we investigates several different tungsten-tantalum alloy materials when exposed to helium ion beam irradiation. The targets are irradiated with 100 eV helium ions at different temperatures (773-1223K) using 1.2 x 1021 ion m-2 s-1 ion flux. Post irradiation characterizations are performed using field-emission scanning electron microscopy (FE-SEM) to study the morphology evolution, optical-reflectivity for monitoring surface deterioration, X-ray photoelectron spectroscopy (XPS) to verify alloy concentrations, and X-ray diffraction (XRD) to analyze crystallographic changes in the samples due to alloying. Future work is discussed about the use of thermal desorption spectroscopy (TDS) to investigate the retention properties of tungsten-tantalum alloys.
24. ELMs-like Transient Heat load Induced Recrystallization and Grain Growth in Molybdenum
24. ELMs-like Transient Heat load Induced Recrystallization and Grain Growth in Molybdenum
Nowadays, tungsten (W), as compared to to other high-Z, refractory metals is the preeminent choice for plasma facing components in modern reactors and ITER divertor. Although series of attempts have been tried, however the physical mechanism of ELM-like transient heat response leading to recrystallization and grain growth is not very clear yet.Therefore the study of similar phenomena on other refractory high-Z metal surfaces, such as molybdenum (Mo), is worthwhile. In the present study a long pulse Nd:YAG (λ:1064 nm) laser operating with a pulse duration of 1±0.1 ms will be used to simulate the transient heat load events on the mirror finished polished Mo samples. The transient heat load will be applied as function of laser pulses ranging between 10-1000. Surface -morphology, -depth information, and –deterioration will be monitored by field-emission scanning electron (FE-SEM), atomic force (AFM) –microscopy, focused ion beam (FIB), and optical-reflectivity measurements, respectively.
Nowadays, tungsten (W), as compared to to other high-Z, refractory metals is the preeminent choice for plasma facing components in modern reactors and ITER divertor. Although series of attempts have been tried, however the physical mechanism of ELM-like transient heat response leading to recrystallization and grain growth is not very clear yet.Therefore the study of similar phenomena on other refractory high-Z metal surfaces, such as molybdenum (Mo), is worthwhile. In the present study a long pulse Nd:YAG (λ:1064 nm) laser operating with a pulse duration of 1±0.1 ms will be used to simulate the transient heat load events on the mirror finished polished Mo samples. The transient heat load will be applied as function of laser pulses ranging between 10-1000. Surface -morphology, -depth information, and –deterioration will be monitored by field-emission scanning electron (FE-SEM), atomic force (AFM) –microscopy, focused ion beam (FIB), and optical-reflectivity measurements, respectively.
23. Structural Response of Hafnium to Low Energy Helium Ion Irradiation in Extreme Conditions for Future Fusion Devices
23. Structural Response of Hafnium to Low Energy Helium Ion Irradiation in Extreme Conditions for Future Fusion Devices
Currently, tungsten remains the best candidate for plasma facing components (PFCs) for future fusion devices because of its high melting point, low erosion, and strong mechanical properties [1]. However, continued investigation of tungsten has shown tungsten to undergo severe morphology changes such as the formation of blisters, bubbles, and fuzz-like nanostructures under low energy, high fluence Helium irradiations under fusion-like conditions [2,3]. This has prompted the investigation of other high-Z refractory metals, viz., Hafnium (Hf), Molybdenum, and Tantalum etc. to better understand the morphology evolution mechanistically and discover possible alternatives to tungsten as a PFC.
Currently, tungsten remains the best candidate for plasma facing components (PFCs) for future fusion devices because of its high melting point, low erosion, and strong mechanical properties [1]. However, continued investigation of tungsten has shown tungsten to undergo severe morphology changes such as the formation of blisters, bubbles, and fuzz-like nanostructures under low energy, high fluence Helium irradiations under fusion-like conditions [2,3]. This has prompted the investigation of other high-Z refractory metals, viz., Hafnium (Hf), Molybdenum, and Tantalum etc. to better understand the morphology evolution mechanistically and discover possible alternatives to tungsten as a PFC.
The work presented here focuses on the response of Hf to low energy, high fluence helium ion irradiation. Specifically, helium ion irradiations were performed Hf targets (10 mm x 10 mm x 0.25 mm) sheets having a purity of 99.95%. The targets were irradiated with 100 eV helium ions at different temperatures (773- 1223K), fluences (3.6 x 1023 – 2.0 x 1025 ions m-2), having a constant 1.2 x 1021 ion m-2 s-1 ion flux. Post irradiation analysis of the Hf samples was performed using field-emission scanning electron microscopy (FE-SEM) to see the morphology evolution, thermal desorption spectroscopy (TDS) to reveal the retention properties of the Hf samples, and optical-reflectivity measurements for monitoring the surface deterioration due to helium ion irradiation at elevated temperatures. These techniques are also supported by X-ray photoelectron spectroscopy (XPS) for impurity and oxidation analysis and Ffocused ion beam (FIB) analysis to provide depth information on the resultant morphology. Differences in observed surface evolution are discussed in the context of leading PFC candidates. This includes identification of operational windows in which fuzz-nanostructure is observed. Recent results show the development of fuzz at a temperature of 1223 K but only 400-600 nm pores are present at temperatures of 1073K. Conclusions regarding Hf responses to fusion like conditions are presented in comparison to published work on other fusion candidate materials.
The work presented here focuses on the response of Hf to low energy, high fluence helium ion irradiation. Specifically, helium ion irradiations were performed Hf targets (10 mm x 10 mm x 0.25 mm) sheets having a purity of 99.95%. The targets were irradiated with 100 eV helium ions at different temperatures (773- 1223K), fluences (3.6 x 1023 – 2.0 x 1025 ions m-2), having a constant 1.2 x 1021 ion m-2 s-1 ion flux. Post irradiation analysis of the Hf samples was performed using field-emission scanning electron microscopy (FE-SEM) to see the morphology evolution, thermal desorption spectroscopy (TDS) to reveal the retention properties of the Hf samples, and optical-reflectivity measurements for monitoring the surface deterioration due to helium ion irradiation at elevated temperatures. These techniques are also supported by X-ray photoelectron spectroscopy (XPS) for impurity and oxidation analysis and Ffocused ion beam (FIB) analysis to provide depth information on the resultant morphology. Differences in observed surface evolution are discussed in the context of leading PFC candidates. This includes identification of operational windows in which fuzz-nanostructure is observed. Recent results show the development of fuzz at a temperature of 1223 K but only 400-600 nm pores are present at temperatures of 1073K. Conclusions regarding Hf responses to fusion like conditions are presented in comparison to published work on other fusion candidate materials.
References:
References:
[1] J. W. Davis, VR Barabash, A Makhankov, et al., J. Nucl. Mater., 258 (1998)
[1] J. W. Davis, VR Barabash, A Makhankov, et al., J. Nucl. Mater., 258 (1998)
[2] D. Nishijima , MY Ye, N Ohno and S Takamura, J. Nucl. Mater. 329 (2004)
[2] D. Nishijima , MY Ye, N Ohno and S Takamura, J. Nucl. Mater. 329 (2004)
[3] S. Kajita, W Sakaguchi, N Ohno, et al., Nucl. Fusion 49 (2009)
[3] S. Kajita, W Sakaguchi, N Ohno, et al., Nucl. Fusion 49 (2009)
22. Temperature Dependent Surface Modifications of Niobium by Low Energy He+ Ion Irradiation
22. Temperature Dependent Surface Modifications of Niobium by Low Energy He+ Ion Irradiation
In future fusion devices, the plasma-facing components (PFCs) will be subjected to externally high thermal loads and high-fluence helium radiation damages. Although, tungsten is considered the most promising material for PFCs in the current nuclear fusion reactors, the physical mechanism responsible for surface deterioration, viz., blisters, bubbles, and fuzz-like nanostructures under low energy, high fluence helium ion (He+) irradiations is not very clear yet. Therefore, studying similar structures on other high-Z refractory metal surfaces, such as Niobium (Nb), as in the presnt case, is worthwhile. The present study shows significant and unique surface microstructural changes in Nb, induced by high-fluence He+ ion irradiation with simultaneous target (sample) annealing. Mirror finished polished Nb samples (10 mm ´ 10 mm ´ 0.5 mm) were irradiated at a normal incidence with 100 eV He+ ions using a constant ion-fluence 8.2 ´ 1024 ions m-2 (flux 1.2 × 1021 ions m-2 s-1) as a function of target temperature in the range of 773 – 1223K. The resulting surface morphology changes were characterized using field-emission scanning electron microscopy (FE-SEM), and chemical composition changes were monitored with ex-situ high-resolution X-ray photoelectron spectroscopy (XPS). Nb Fuzz structures and significant microstructural changes due to helium ion irradiations have been observed. The study is in progress for elucidating the possible driving mechanisms of these structures, as well as the possible temperature window for Nb Fuzz formation. In addition, optical-reflectivity and thermal desorption spectroscopy (TDS) results on these surfaces will also be discussed for putting more insight in the understanding of the physical mechanism of surface deteriorations due to low energy He+ ion irradiation in exterame conditions.
In future fusion devices, the plasma-facing components (PFCs) will be subjected to externally high thermal loads and high-fluence helium radiation damages. Although, tungsten is considered the most promising material for PFCs in the current nuclear fusion reactors, the physical mechanism responsible for surface deterioration, viz., blisters, bubbles, and fuzz-like nanostructures under low energy, high fluence helium ion (He+) irradiations is not very clear yet. Therefore, studying similar structures on other high-Z refractory metal surfaces, such as Niobium (Nb), as in the presnt case, is worthwhile. The present study shows significant and unique surface microstructural changes in Nb, induced by high-fluence He+ ion irradiation with simultaneous target (sample) annealing. Mirror finished polished Nb samples (10 mm ´ 10 mm ´ 0.5 mm) were irradiated at a normal incidence with 100 eV He+ ions using a constant ion-fluence 8.2 ´ 1024 ions m-2 (flux 1.2 × 1021 ions m-2 s-1) as a function of target temperature in the range of 773 – 1223K. The resulting surface morphology changes were characterized using field-emission scanning electron microscopy (FE-SEM), and chemical composition changes were monitored with ex-situ high-resolution X-ray photoelectron spectroscopy (XPS). Nb Fuzz structures and significant microstructural changes due to helium ion irradiations have been observed. The study is in progress for elucidating the possible driving mechanisms of these structures, as well as the possible temperature window for Nb Fuzz formation. In addition, optical-reflectivity and thermal desorption spectroscopy (TDS) results on these surfaces will also be discussed for putting more insight in the understanding of the physical mechanism of surface deteriorations due to low energy He+ ion irradiation in exterame conditions.
21. Structural response of transient head loading on molybdenum surface exposed to low-energy helium plasma
21. Structural response of transient head loading on molybdenum surface exposed to low-energy helium plasma
One of the most important challenges in developing commercial fusion reactors is understanding how the plasma interacts with the walls of a tokamak. Transient events within the plasma, such as type-I ELMs, deposit a large amount of energy onto plasma facing components (PFCs), which can cause serious material damage. However, recent research done on tungsten has shown that plasma instabilities can actually remove helium-induced, fibre-form nanostructures from the surface. Currently tungsten is considered the most promising material for PFCs. However, other high-Z, refractory metals need to be examined to find the optimum material and the best operating windows for each reactor PFCs.
One of the most important challenges in developing commercial fusion reactors is understanding how the plasma interacts with the walls of a tokamak. Transient events within the plasma, such as type-I ELMs, deposit a large amount of energy onto plasma facing components (PFCs), which can cause serious material damage. However, recent research done on tungsten has shown that plasma instabilities can actually remove helium-induced, fibre-form nanostructures from the surface. Currently tungsten is considered the most promising material for PFCs. However, other high-Z, refractory metals need to be examined to find the optimum material and the best operating windows for each reactor PFCs.
To simulate type-I ELMs, an Nd:YAG laser is being used with a pulse width of ~ 1 ms and a pulse energy between 0.16 J and 1.49 J, which corresponds to similar heat load conditions of type-I ELMs. The two types of targets are pristine molybdenum and nanostructured molybdenum. Nanostructured molybdenum is being synthesized by bombarding the surface with helium plasma under different temperatures and ion energies to simulate conditions during normal operations. On each target, multiple experiments were performed, varying the number of shots. Preliminary results indicate that the nanostructured damage is being removed at as little as 25 shots at a heat load of ~ 1.13 MJ/m2, which is within the expected heat load of type-I ELMs. However, analysis done using a scanning electron microscope shows that there may still be small, individual nanostructure fibres on the surface after laser bombardment. Nevertheless, at around 500 shots at energy of 1.13 MJ/m2, these nanostructures seem to disappear. More analysis should be done to determine the effectiveness of transient heat loading in either removing or reparing this nanostructure “fuzz” using reflectivity analysis on bombarded spots We are XPS and TDS on a witness plate to investigate the mechanisms governing the removal of these nano-fibres. Finally, understanding the evolution of thermo-mechanical properties, such as tensile stress, ductile-to-brittle transition, and melting splash, before and after laser irradiation is critical in understanding the overall effects of transient events such as type-I ELMs and disruptions on PFCs.
To simulate type-I ELMs, an Nd:YAG laser is being used with a pulse width of ~ 1 ms and a pulse energy between 0.16 J and 1.49 J, which corresponds to similar heat load conditions of type-I ELMs. The two types of targets are pristine molybdenum and nanostructured molybdenum. Nanostructured molybdenum is being synthesized by bombarding the surface with helium plasma under different temperatures and ion energies to simulate conditions during normal operations. On each target, multiple experiments were performed, varying the number of shots. Preliminary results indicate that the nanostructured damage is being removed at as little as 25 shots at a heat load of ~ 1.13 MJ/m2, which is within the expected heat load of type-I ELMs. However, analysis done using a scanning electron microscope shows that there may still be small, individual nanostructure fibres on the surface after laser bombardment. Nevertheless, at around 500 shots at energy of 1.13 MJ/m2, these nanostructures seem to disappear. More analysis should be done to determine the effectiveness of transient heat loading in either removing or reparing this nanostructure “fuzz” using reflectivity analysis on bombarded spots We are XPS and TDS on a witness plate to investigate the mechanisms governing the removal of these nano-fibres. Finally, understanding the evolution of thermo-mechanical properties, such as tensile stress, ductile-to-brittle transition, and melting splash, before and after laser irradiation is critical in understanding the overall effects of transient events such as type-I ELMs and disruptions on PFCs.
20. Effect of Low Energy He+ Ion Irradiation on Surface Morphology, Mechanical Properties, and Fracture Behaviour of Molybdenum
20. Effect of Low Energy He+ Ion Irradiation on Surface Morphology, Mechanical Properties, and Fracture Behaviour of Molybdenum
PIRE student workshop at Center for Materials under Extreme Environment (CMUXE), School of Nuclear Engineering, Purdue University, USA, May 11-12, 2015
PIRE student workshop at Center for Materials under Extreme Environment (CMUXE), School of Nuclear Engineering, Purdue University, USA, May 11-12, 2015
In the present study we report on the effect of 100eV He+ ion irradiation (ion flux: 7.2 x 1020 ions m-2 s-1, ion fluence: 2.6 x 1024 ions m-2) on surface morphology, mechanical properties, and fracture behaviour of Molybdenum (Mo). Rectangular tensile unnotched specimens and single edge notched specimens of 75 × 12.7 × 0.78 mm were cut along the rolling direction. Ion irradiation experiment were performed at two target temperatures, 873 and 923K at normal incidence. The selection the target temperature was based on the Mo fuzz formation temperature window ,823 K<,Mo fuzz< 1073K [1]. Surface morphology and deterioration were studied using field emission scanning electron microscopy (FE-SEM) and optical-reflectivity measurements. The mechanical and fracture behavior of above ion irradiation exposed Mo samples were evaluated and compared with pristine Sample.
In the present study we report on the effect of 100eV He+ ion irradiation (ion flux: 7.2 x 1020 ions m-2 s-1, ion fluence: 2.6 x 1024 ions m-2) on surface morphology, mechanical properties, and fracture behaviour of Molybdenum (Mo). Rectangular tensile unnotched specimens and single edge notched specimens of 75 × 12.7 × 0.78 mm were cut along the rolling direction. Ion irradiation experiment were performed at two target temperatures, 873 and 923K at normal incidence. The selection the target temperature was based on the Mo fuzz formation temperature window ,823 K<,Mo fuzz< 1073K [1]. Surface morphology and deterioration were studied using field emission scanning electron microscopy (FE-SEM) and optical-reflectivity measurements. The mechanical and fracture behavior of above ion irradiation exposed Mo samples were evaluated and compared with pristine Sample.
References:
References:
(1) J. K. Tripathi, T. J. Novakowski, G. Joseph, J. Linke, and A. Hassanein J. Nucl. Mater. (in-press)
(1) J. K. Tripathi, T. J. Novakowski, G. Joseph, J. Linke, and A. Hassanein J. Nucl. Mater. (in-press)
19. Effect of He+ Ion Irradiation on Zirconium Microstructures Under Extreme Conditions
19. Effect of He+ Ion Irradiation on Zirconium Microstructures Under Extreme Conditions
The 2015 Undergraduate Research and Poster Symposium, Purdue University, April 14, 2015
The 2015 Undergraduate Research and Poster Symposium, Purdue University, April 14, 2015
The safe and continued operation of the US nuclear power plants requires improvement of the radiation resistant properties of materials used in nuclear reactors. Zirconium is a material of particular interest due to its use in fuel cladding. Studies performed on other materials have shown that grain boundaries can play a significant role on the radiation resistant properties of a material. Thus, the focus of our research is to investigate the performance of various zirconium samples under extreme conditions (similar to those in commercial nuclear reactors). Analysis of the surface morphology of zirconium both pre- and post-irradiation was conducted with Scanning Electron Microscopy (SEM). Cold-rolled (small-grain microstructure) and annealed (large-grained microstructure) zirconium samples were mechanically polished in order to be irradiated. Room temperature irradiation of zirconium samples was conducted at energies of 100 eV and 1000 eV with He+ ions at a flux of 1 x 1020 ion m-2 s-1 using a gridded ion source. High temperature (623 and 973K) He+ irradiations were performed with 100 eV He+ ions using a gridless end-hall ion source at the same flux. Transmission Electron Microscopy (TEM) was conducted to determine the grain size of the zirconium samples. Preliminary results show greater surface damage on the rolled zirconium samples than on the annealed samples for all irradiation cases. The difference in damage was most evident in high temperature irradiations. Further work is necessary to evaluate why the small-grain zirconium exhibited greater damage. Future testing will be performed using higher fluxes, temperatures and energies.
The safe and continued operation of the US nuclear power plants requires improvement of the radiation resistant properties of materials used in nuclear reactors. Zirconium is a material of particular interest due to its use in fuel cladding. Studies performed on other materials have shown that grain boundaries can play a significant role on the radiation resistant properties of a material. Thus, the focus of our research is to investigate the performance of various zirconium samples under extreme conditions (similar to those in commercial nuclear reactors). Analysis of the surface morphology of zirconium both pre- and post-irradiation was conducted with Scanning Electron Microscopy (SEM). Cold-rolled (small-grain microstructure) and annealed (large-grained microstructure) zirconium samples were mechanically polished in order to be irradiated. Room temperature irradiation of zirconium samples was conducted at energies of 100 eV and 1000 eV with He+ ions at a flux of 1 x 1020 ion m-2 s-1 using a gridded ion source. High temperature (623 and 973K) He+ irradiations were performed with 100 eV He+ ions using a gridless end-hall ion source at the same flux. Transmission Electron Microscopy (TEM) was conducted to determine the grain size of the zirconium samples. Preliminary results show greater surface damage on the rolled zirconium samples than on the annealed samples for all irradiation cases. The difference in damage was most evident in high temperature irradiations. Further work is necessary to evaluate why the small-grain zirconium exhibited greater damage. Future testing will be performed using higher fluxes, temperatures and energies.
18. He+ ion Irradiation on Tungsten Surface in Extreme Conditions
18. He+ ion Irradiation on Tungsten Surface in Extreme Conditions
Summer Undergraduate Research Fellowships (SURF) program, Neil Armstrong Hall of Engineering, Purdue University, West Lafayette, IN 47907, August 7, 2014
Summer Undergraduate Research Fellowships (SURF) program, Neil Armstrong Hall of Engineering, Purdue University, West Lafayette, IN 47907, August 7, 2014
Higher melting point (3695K), lower sputtering yield and most importantly, lower in-bulk, and co-deposit retention at elevated temperature makes tungsten (W) as a potential candidate for plasma-facing component (PFC) in the international thermonuclear experimental reactor (ITER)-divertor. Helium ion (He+) bombardment on W can cause wide variety of microstructural evolution, such as dislocation loops, helium holes/bubbles and fibre-form nanostructures (Fuzz) etc. In this work, 100 eV He+ ion irradiation, at temperature ranges from 500°C to 1000°C, will be performed on mechanically polished mirror like W surfaces. The surface modification and compositional analysis, due to ion irradiation, will be studied using Scanning electron- (SEM) and Atomic force- (AFM) microscopy and X-ray photoelectron spectroscopy (XPS), respectively. The formation of fibre-form nanostructures was observed for temperatures in the range of 650°C to 1000°C. It was also noted that the incident ion energy and the fluence, that the material underwent, were crucial parameters for fibre-form nanostructure formation.
Higher melting point (3695K), lower sputtering yield and most importantly, lower in-bulk, and co-deposit retention at elevated temperature makes tungsten (W) as a potential candidate for plasma-facing component (PFC) in the international thermonuclear experimental reactor (ITER)-divertor. Helium ion (He+) bombardment on W can cause wide variety of microstructural evolution, such as dislocation loops, helium holes/bubbles and fibre-form nanostructures (Fuzz) etc. In this work, 100 eV He+ ion irradiation, at temperature ranges from 500°C to 1000°C, will be performed on mechanically polished mirror like W surfaces. The surface modification and compositional analysis, due to ion irradiation, will be studied using Scanning electron- (SEM) and Atomic force- (AFM) microscopy and X-ray photoelectron spectroscopy (XPS), respectively. The formation of fibre-form nanostructures was observed for temperatures in the range of 650°C to 1000°C. It was also noted that the incident ion energy and the fluence, that the material underwent, were crucial parameters for fibre-form nanostructure formation.
17. The Role of Surface Roughness on Ion Sputtering Yield Measurements with a QCM
17. The Role of Surface Roughness on Ion Sputtering Yield Measurements with a QCM
Summer Undergraduate Research Fellowships (SURF) program, Neil Armstrong Hall of Engineering, Purdue University, West Lafayette, IN 47907, July 31, 2013
Summer Undergraduate Research Fellowships (SURF) program, Neil Armstrong Hall of Engineering, Purdue University, West Lafayette, IN 47907, July 31, 2013
Ion sputtering, i.e. removal of surface atoms or molecules of a solid under energetic ion irradiation is an interesting and a well-studied phenomenon. However, in addition, the field is still very promising for its applications in materials modification and their characterization as well as for the basic understanding of the mechanism of the process. In fact, the sputtering yield, defined as the average number of atoms removed from a sample per incident ion, is a crucial parameter in these experiments. In the present study, a quartz crystal microbalance (QCM) was used for measuring the sputtering yield values. Our experiment observation shows significantly higher sputtering yield values than that of the theoretically calculated ones, using SRIM simulations. In addition, we observed a significant reduction in the sputtering yield values with time, for a constant ion energy bombardment. Similarly, atomic force microscopy (AFM) study shows a significant reduction in the surface roughness values for a longer period of ion bombardment. These observations suggest that surface topography affects significantly the sputtering yield values.
Ion sputtering, i.e. removal of surface atoms or molecules of a solid under energetic ion irradiation is an interesting and a well-studied phenomenon. However, in addition, the field is still very promising for its applications in materials modification and their characterization as well as for the basic understanding of the mechanism of the process. In fact, the sputtering yield, defined as the average number of atoms removed from a sample per incident ion, is a crucial parameter in these experiments. In the present study, a quartz crystal microbalance (QCM) was used for measuring the sputtering yield values. Our experiment observation shows significantly higher sputtering yield values than that of the theoretically calculated ones, using SRIM simulations. In addition, we observed a significant reduction in the sputtering yield values with time, for a constant ion energy bombardment. Similarly, atomic force microscopy (AFM) study shows a significant reduction in the surface roughness values for a longer period of ion bombardment. These observations suggest that surface topography affects significantly the sputtering yield values.
16. Sputtering Yield Measurement By Quartz Crystal Microbalance (QCM)
16. Sputtering Yield Measurement By Quartz Crystal Microbalance (QCM)
Summer Undergraduate Research Fellowships (SURF) program, Neil Armstrong Hall of Engineering, Purdue University, West Lafayette, IN 47907, July 31, 2013
Summer Undergraduate Research Fellowships (SURF) program, Neil Armstrong Hall of Engineering, Purdue University, West Lafayette, IN 47907, July 31, 2013
Quartz-crystal microbalance (QCM) has been used as a sensitive device for the measurement of small mass changes from a long ago. In fact, using QCM we can measure the differential sputtering yield profile of a material, over a hemisphere above the target, very precisely. The sputtering yield depends on properties of both the incident particles (energy, mass, and incidence angle) and the target (mass, surface binding energy, surface topography, and even the crystal orientation). In our present study, we used a highly sensitive QCM to detect the mass change of the electrode material (gold and silver) through oscillations and calculated the corresponding sputtering yields. We used two types of ions, e.g, He and Ar. Our experiment observation shows significantly higher sputtering yield values than that of the theoretically calculated ones, using SRIM simulations. In addition, we observed a significant reduction in the sputtering yield values with time, for a constant ion energy bombardment. Similarly, atomic force microscopy (AFM) study shows a significant reduction in the surface roughness values for a longer period of ion bombardment. These observations suggest that surface topography affects significantly the sputtering yield values. In our presentation, I shall discuss these issues in detail.
Quartz-crystal microbalance (QCM) has been used as a sensitive device for the measurement of small mass changes from a long ago. In fact, using QCM we can measure the differential sputtering yield profile of a material, over a hemisphere above the target, very precisely. The sputtering yield depends on properties of both the incident particles (energy, mass, and incidence angle) and the target (mass, surface binding energy, surface topography, and even the crystal orientation). In our present study, we used a highly sensitive QCM to detect the mass change of the electrode material (gold and silver) through oscillations and calculated the corresponding sputtering yields. We used two types of ions, e.g, He and Ar. Our experiment observation shows significantly higher sputtering yield values than that of the theoretically calculated ones, using SRIM simulations. In addition, we observed a significant reduction in the sputtering yield values with time, for a constant ion energy bombardment. Similarly, atomic force microscopy (AFM) study shows a significant reduction in the surface roughness values for a longer period of ion bombardment. These observations suggest that surface topography affects significantly the sputtering yield values. In our presentation, I shall discuss these issues in detail.
15. Stoichiometry Analysis of Bulk YBCO Using XPS
15. Stoichiometry Analysis of Bulk YBCO Using XPS
The 35 Annual symposium on Applied Surface Analysis, Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana-Champaign, USA, June 5-7, 2013
The 35 Annual symposium on Applied Surface Analysis, Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana-Champaign, USA, June 5-7, 2013
X-ray photoelectron spectroscopy (XPS) is a widely used technique in surface analysis to measure the elemental composition and chemical state of the elements of a material. Imaging-XPS (iXPS) provides useful information of elemental distribution in a target of interest and it is performed by selecting a binding energy representing a transition for a certain element. We investigated elemental distribution in a high Tc superconductor YBa2Cu3O7 (YBCO) using iXPS. The experiments were performed in the IMPACT facility at the Center for Materials Under Extreme Environments (CMUXE) at Purdue University which contains an UHV chamber equipped with a suite of in-situ diagnostic tools for surface analysis. The XPS measurements were performed using a Mg-Kα radiation source and the emitted photoelectrons were analyzed using a Omicron Argus hemispherical electron analyzer. The various elemental distributions in the bulk YBCO target were obtained using iXPS and used for stoichiometric analysis.
X-ray photoelectron spectroscopy (XPS) is a widely used technique in surface analysis to measure the elemental composition and chemical state of the elements of a material. Imaging-XPS (iXPS) provides useful information of elemental distribution in a target of interest and it is performed by selecting a binding energy representing a transition for a certain element. We investigated elemental distribution in a high Tc superconductor YBa2Cu3O7 (YBCO) using iXPS. The experiments were performed in the IMPACT facility at the Center for Materials Under Extreme Environments (CMUXE) at Purdue University which contains an UHV chamber equipped with a suite of in-situ diagnostic tools for surface analysis. The XPS measurements were performed using a Mg-Kα radiation source and the emitted photoelectrons were analyzed using a Omicron Argus hemispherical electron analyzer. The various elemental distributions in the bulk YBCO target were obtained using iXPS and used for stoichiometric analysis.
14. Magnetic Behavior of Non-magnetic Materials: Superparamagnetism in Mesoscopically Self-ordered FeSi2 Nanoisland Arrays
14. Magnetic Behavior of Non-magnetic Materials: Superparamagnetism in Mesoscopically Self-ordered FeSi2 Nanoisland Arrays
MRS Spring Meeting & Exhibit, San Francisco, California, April 1-5, 2013
MRS Spring Meeting & Exhibit, San Francisco, California, April 1-5, 2013
Self-assembled α-FeSi2 nanoislands were epitaxially grown on vicinal Si(111) surfaces by room-temperature evaporation of low (~1 ML) and high (~20 ML) Fe coverage, followed by elevated-temperature annealing. Evolution of such Fe/Si(111) surfaces, as a function of Fe-coverage and annealing temperature, was studied in-situ by time-resolved scanning tunneling microscopy (STM), and ex-situ by x-ray photoelectron spectroscopy (XPS), aberration-corrected high-resolution transmission electron microscopy (HRTEM), and superconducting quantum interference device (SQUID) magnetometry. At a low Fe-covered surface, the initially two-dimensional (2×2)-reconstructed Fe-silicide layer transformed at higher annealing temperatures into (2×2)-reconstructed nanoislands, decorating the step-bunch edges at a vicinal Si(111) surface in a self-ordered fashion. In contrast, the silicide nanoislands at a high Fe-covered surface were noticeably larger, more three-dimensional, and randomly distributed all over the surface, lacking any visible positional correlations. SQUID magnetometry showed considerable superparamagnetism (~1.9 μB/ Fe atom at 4K) in the low Fe-coverage sample, indicating stronger ferromagnetic coupling of individual magnetic moments than in the high Fe-coverage sample (with only ~0.8 μB / Fe atom). As our XPS and HRTEM analyses indicated formation of the same α-FeSi2 island phase (non-magnetic in the bulk form) in both samples, and even the same α-FeSi2{112}||Si{111} orientation, the profoundly different magnetic properties must have been a direct consequence of the corresponding nanoisland morphological differences, including size, shape, and mesoscopic ordering. Such anomalous magnetic behavior of the α-FeSi2 nanoislands, most notably in low Fe coverage case, is radically different from the non-magnetic bulk α-FeSi2 phase, and may open new pathways to spintronics and high-density magnetic data storage devices.
Self-assembled α-FeSi2 nanoislands were epitaxially grown on vicinal Si(111) surfaces by room-temperature evaporation of low (~1 ML) and high (~20 ML) Fe coverage, followed by elevated-temperature annealing. Evolution of such Fe/Si(111) surfaces, as a function of Fe-coverage and annealing temperature, was studied in-situ by time-resolved scanning tunneling microscopy (STM), and ex-situ by x-ray photoelectron spectroscopy (XPS), aberration-corrected high-resolution transmission electron microscopy (HRTEM), and superconducting quantum interference device (SQUID) magnetometry. At a low Fe-covered surface, the initially two-dimensional (2×2)-reconstructed Fe-silicide layer transformed at higher annealing temperatures into (2×2)-reconstructed nanoislands, decorating the step-bunch edges at a vicinal Si(111) surface in a self-ordered fashion. In contrast, the silicide nanoislands at a high Fe-covered surface were noticeably larger, more three-dimensional, and randomly distributed all over the surface, lacking any visible positional correlations. SQUID magnetometry showed considerable superparamagnetism (~1.9 μB/ Fe atom at 4K) in the low Fe-coverage sample, indicating stronger ferromagnetic coupling of individual magnetic moments than in the high Fe-coverage sample (with only ~0.8 μB / Fe atom). As our XPS and HRTEM analyses indicated formation of the same α-FeSi2 island phase (non-magnetic in the bulk form) in both samples, and even the same α-FeSi2{112}||Si{111} orientation, the profoundly different magnetic properties must have been a direct consequence of the corresponding nanoisland morphological differences, including size, shape, and mesoscopic ordering. Such anomalous magnetic behavior of the α-FeSi2 nanoislands, most notably in low Fe coverage case, is radically different from the non-magnetic bulk α-FeSi2 phase, and may open new pathways to spintronics and high-density magnetic data storage devices.
13. HRTEM study of self-assembled superparamagnetic iron-silicide nanoislands
13. HRTEM study of self-assembled superparamagnetic iron-silicide nanoislands
The 15th European Microscopy Congress Manchester Central, United Kingdom, September 16 – 21, 2012
The 15th European Microscopy Congress Manchester Central, United Kingdom, September 16 – 21, 2012
12. Quantitative HRTEM Study of the Structure and Interface of Self-Assembled Metal-Silicide Nanoislands
12. Quantitative HRTEM Study of the Structure and Interface of Self-Assembled Metal-Silicide Nanoislands
The 45th Annual Scientific Meeting of Israel Society of Microscopy (ISM), Kibbutz Hagoshrim, Israel MAY 25-26, 2011
The 45th Annual Scientific Meeting of Israel Society of Microscopy (ISM), Kibbutz Hagoshrim, Israel MAY 25-26, 2011
11. Quantitative HRTEM Study of Self-Assembled Metal-Silicide Nanoislands
11. Quantitative HRTEM Study of Self-Assembled Metal-Silicide Nanoislands
International Microscopy Congress (IMC17), Rio de Janeiro, Brazil, September 19-24, 2010
International Microscopy Congress (IMC17), Rio de Janeiro, Brazil, September 19-24, 2010
10. Analytical High-Resolution Transmission Electron Microscopy of Self-Assembled Metal-Silicide Nanoislands
10. Analytical High-Resolution Transmission Electron Microscopy of Self-Assembled Metal-Silicide Nanoislands
The 44th Annual Scientific Meeting of ISM (Israel Society for Microscopy), Tel-Aviv University, Ramat Aviv, Israel, May 31, 2010
The 44th Annual Scientific Meeting of ISM (Israel Society for Microscopy), Tel-Aviv University, Ramat Aviv, Israel, May 31, 2010
9. Self-Organization and Magic-heights of CoSi2 and TiSi2 Nanoislands on Si(111) substrates
9. Self-Organization and Magic-heights of CoSi2 and TiSi2 Nanoislands on Si(111) substrates
14th Israel Materials Engineering Conference (IMEC-14), Tel Aviv University, Ramat Aviv, Israel December 13-14 (2009)
14th Israel Materials Engineering Conference (IMEC-14), Tel Aviv University, Ramat Aviv, Israel December 13-14 (2009)
Replacement of contemporary sub-micron electronic devices by those based on self-organized nanostructures is the next naturally expected step in the continuous miniaturization trend. For this to happen, it is necessary tocontrol the size, shape and uniformity of self-assembled and self-organized nanoislands. The importance ofunderstanding the physics behind epitaxial island growth by self-assembly accounts for a vast amount of workinvested in this field. The aim of this work is to explore the tendency of hetroepitaxial silicide nanoislands toself-organize on Si (111) surfaces. More specifically, we wish to explore the effect of the evaporated species (Ti and Co in this case), their initial coverage, surface vicinality, and post-deposition annealing treatments on the degree of order of silicide islands epitaxially grown in ultra-high vacuum.
Replacement of contemporary sub-micron electronic devices by those based on self-organized nanostructures is the next naturally expected step in the continuous miniaturization trend. For this to happen, it is necessary tocontrol the size, shape and uniformity of self-assembled and self-organized nanoislands. The importance ofunderstanding the physics behind epitaxial island growth by self-assembly accounts for a vast amount of workinvested in this field. The aim of this work is to explore the tendency of hetroepitaxial silicide nanoislands toself-organize on Si (111) surfaces. More specifically, we wish to explore the effect of the evaporated species (Ti and Co in this case), their initial coverage, surface vicinality, and post-deposition annealing treatments on the degree of order of silicide islands epitaxially grown in ultra-high vacuum.
We report on correlations between the initial Si(111) surface step-terrace morphological configuration(dependent on the degree of surface miscut) and the size & shape distributions of the grown silicide islands.More specifically, the position of the island sites on a vicinal Si(111) surface was observed to be affected by the step-island and islands-islands interactions, leading to their in-plane self-organization along specific azimuthal directions. Furthermore, we found evidence that, in addition to a strain energy, which acts to destabilize flat topislands and promote transition to three-dimensional growth - electronic energy tends to stabilize flat islands ofcertain (“magic”) heights.
We report on correlations between the initial Si(111) surface step-terrace morphological configuration(dependent on the degree of surface miscut) and the size & shape distributions of the grown silicide islands.More specifically, the position of the island sites on a vicinal Si(111) surface was observed to be affected by the step-island and islands-islands interactions, leading to their in-plane self-organization along specific azimuthal directions. Furthermore, we found evidence that, in addition to a strain energy, which acts to destabilize flat topislands and promote transition to three-dimensional growth - electronic energy tends to stabilize flat islands ofcertain (“magic”) heights.
8. Modifications in structural and optical properties of Mn-ion implanted CdS thin films
8. Modifications in structural and optical properties of Mn-ion implanted CdS thin films
2nd International Conference on Physics at Surfaces and Interfaces (PSI2009), Puri, India, February 23 – 27, 2009
2nd International Conference on Physics at Surfaces and Interfaces (PSI2009), Puri, India, February 23 – 27, 2009
7. Ion induced modification in structural and magnetic properties of Pt/Cr/Co multilayers
7. Ion induced modification in structural and magnetic properties of Pt/Cr/Co multilayers
Homi Bhabha Centenary DAE-BRNS National Conference & HRI School on 'Spintronic and Magnetoelectronic Materials and Devices, Puri, India, January 8-10, 2009
Homi Bhabha Centenary DAE-BRNS National Conference & HRI School on 'Spintronic and Magnetoelectronic Materials and Devices, Puri, India, January 8-10, 2009
6. Mn+ implanted CdS films: Correlation between structural and optical properties
6. Mn+ implanted CdS films: Correlation between structural and optical properties
Second International Conference on Frontiers in Nanoscience and Technology, (Cochin Nano-2009), Cochin, India, January 3-6, 2009
Second International Conference on Frontiers in Nanoscience and Technology, (Cochin Nano-2009), Cochin, India, January 3-6, 2009
The optoelectronic properties such as wide band gap, strong luminescence and photoconductivity discriminate CdS as one among the promising materials in II-VI family for the successful realization of many optoelectronic devices. Doping of CdS with transition metal ions have found to lead interesting results such as band gap modification, enhancement of luminescence, etc, due to the sp-d exchange interaction between the localized d electrons of the transition metal ions and the band electrons. Ion implantation is known to provide many advantages over conventional methods for efficient doping. For instance, it is not governed by equilibrium thermodynamics and offers the advantages of high spatial selectivity, relatively low temperature processing. In this paper, we have made an attempt to correlate the structural and optical properties of 190 keV Mn+ implanted CdS films grown by thermal evaporation on to micro-glass slides. Mn-ion implantation was performed in the fluence range of 1013-1016 ions cm-2 and at two different temperatures, viz. 300 and 573 K. The films were characterized by X-ray diffraction, atomic force microscopy, photoluminescence, and micro-Raman spectroscopy. The Mn2+ related emission, originating from the d-d transition was observed at 2.22 eV, indicates a possible incorporation of Mn+ into CdS lattice. The position of the band edge emission is found to strongly depend on the Mn+ concentration and the temperature. Implantation at higher Mn+ concentration has results improvement in the structural quality of the films. The results would be discussed in terms of ion-solid interaction.
The optoelectronic properties such as wide band gap, strong luminescence and photoconductivity discriminate CdS as one among the promising materials in II-VI family for the successful realization of many optoelectronic devices. Doping of CdS with transition metal ions have found to lead interesting results such as band gap modification, enhancement of luminescence, etc, due to the sp-d exchange interaction between the localized d electrons of the transition metal ions and the band electrons. Ion implantation is known to provide many advantages over conventional methods for efficient doping. For instance, it is not governed by equilibrium thermodynamics and offers the advantages of high spatial selectivity, relatively low temperature processing. In this paper, we have made an attempt to correlate the structural and optical properties of 190 keV Mn+ implanted CdS films grown by thermal evaporation on to micro-glass slides. Mn-ion implantation was performed in the fluence range of 1013-1016 ions cm-2 and at two different temperatures, viz. 300 and 573 K. The films were characterized by X-ray diffraction, atomic force microscopy, photoluminescence, and micro-Raman spectroscopy. The Mn2+ related emission, originating from the d-d transition was observed at 2.22 eV, indicates a possible incorporation of Mn+ into CdS lattice. The position of the band edge emission is found to strongly depend on the Mn+ concentration and the temperature. Implantation at higher Mn+ concentration has results improvement in the structural quality of the films. The results would be discussed in terms of ion-solid interaction.
5. Swift heavy ion beam induced mixing and chemical modifications at the metal/polymer interface,
5. Swift heavy ion beam induced mixing and chemical modifications at the metal/polymer interface,
8th International Symposium on Ionizing Radiation and Polymers, Angra dos Reis/Rio de Janeiro, Brazil, October 12 - 17, 2008
8th International Symposium on Ionizing Radiation and Polymers, Angra dos Reis/Rio de Janeiro, Brazil, October 12 - 17, 2008
The interface mixing in Ni/teflon and Au/Teflon systems, have been investigated as a function of the morphological and chemical modifications induced by 120 MeV Au ions with fluences ranging from 1 x 1012 to 5 x 1013 ions/cm2. Rutherford Backscattering Spectroscopy (RBS) and Atomic Force Microscopy (AFM) were used to analyze atomic transport at the interface and the resulting roughness and morphology changes at the surface of the samples. Modifications are observed in both the systems but Ni/Teflon system exhibits strong ion beam induced intermixing, while no observable intermixing is observed in the case of Au/Teflon system as observed by RBS. Thermodynamically, swift heavy ion (SHI) induced mixing favors the Ni/teflon system (DHBDE ~ -22.7 KJ/mol), which is more reactive than Au/teflon system (DHBDE ~ -180 KJ/mol). Also Ni as well as teflon is sensitive while Au is insensitive to electronic energy loss (Se). The evolution of roughness at the surface of a Ni film, which effects the observed broadening at the interface, has been taken into consideration and it is found that the observed mixing is not due to the surface roughness. Interface broadening is found to vary nonlinearly with the ion fluence, which indicates that mixing is driven by a solid-state chemical reaction. The changes in the chemical structure at the interface were studied by Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS). The formation of new bonds (Ni-F) as a result of mixing and chain scissoring, cross-linking of the normal chain (-CF=CF2, -CF=C<) by irradiation is confirmed by FTIR. The role of swift heavy ion (SHI) in mixing mechanism of the metal/polymer systems has been discussed.
The interface mixing in Ni/teflon and Au/Teflon systems, have been investigated as a function of the morphological and chemical modifications induced by 120 MeV Au ions with fluences ranging from 1 x 1012 to 5 x 1013 ions/cm2. Rutherford Backscattering Spectroscopy (RBS) and Atomic Force Microscopy (AFM) were used to analyze atomic transport at the interface and the resulting roughness and morphology changes at the surface of the samples. Modifications are observed in both the systems but Ni/Teflon system exhibits strong ion beam induced intermixing, while no observable intermixing is observed in the case of Au/Teflon system as observed by RBS. Thermodynamically, swift heavy ion (SHI) induced mixing favors the Ni/teflon system (DHBDE ~ -22.7 KJ/mol), which is more reactive than Au/teflon system (DHBDE ~ -180 KJ/mol). Also Ni as well as teflon is sensitive while Au is insensitive to electronic energy loss (Se). The evolution of roughness at the surface of a Ni film, which effects the observed broadening at the interface, has been taken into consideration and it is found that the observed mixing is not due to the surface roughness. Interface broadening is found to vary nonlinearly with the ion fluence, which indicates that mixing is driven by a solid-state chemical reaction. The changes in the chemical structure at the interface were studied by Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS). The formation of new bonds (Ni-F) as a result of mixing and chain scissoring, cross-linking of the normal chain (-CF=CF2, -CF=C<) by irradiation is confirmed by FTIR. The role of swift heavy ion (SHI) in mixing mechanism of the metal/polymer systems has been discussed.
4. Modification of the magnetic and the structural properties of Pt/Cr/Co multilayers by He+ ion irradiation
4. Modification of the magnetic and the structural properties of Pt/Cr/Co multilayers by He+ ion irradiation
16th International Conference on Ion Beam Modification of Materials (IBMM), Dresden, Germany, August 31 - September 05 (2008)
16th International Conference on Ion Beam Modification of Materials (IBMM), Dresden, Germany, August 31 - September 05 (2008)
Multilayer thin film structures consisting of alternating layers of different materials particularly, nanostructured in one dimension, have unique structural and magnetic properties. Ion irradiation directly controls the material composition, distribution of defects, and interfaces. It offers a high spatial selectivity and is not driven by equilibrium thermodynamics. Therefore, ion irradiation of multilayer thin films often leads to the formation of metastable phases, which is otherwise not possible by solid state reaction route. It is a unique technique to modify several extrinsic magnetic properties of ultrathin magnetic multilayers, viz. coercivity, magnetic anisotropy, and magnetic exchange coupling in a highly localized region.
Multilayer thin film structures consisting of alternating layers of different materials particularly, nanostructured in one dimension, have unique structural and magnetic properties. Ion irradiation directly controls the material composition, distribution of defects, and interfaces. It offers a high spatial selectivity and is not driven by equilibrium thermodynamics. Therefore, ion irradiation of multilayer thin films often leads to the formation of metastable phases, which is otherwise not possible by solid state reaction route. It is a unique technique to modify several extrinsic magnetic properties of ultrathin magnetic multilayers, viz. coercivity, magnetic anisotropy, and magnetic exchange coupling in a highly localized region.
We report on the He+-ion induced changes in the magnetic and the structural properties of [Pt(2.5 nm) / Cr(0.8 nm) / Co(3.0 nm)]x6/Si multilayer thin films. The multilayer thin films have been irradiated at room temperature with 2 MeV He+ ions in a fluence range of 1 x 1015 to 5.5 x 1016 ions cm-2. X-ray reflectivity (XRR) measurements were performed to determine the layer thicknesses, surface and interface roughness, and the electron density of individual layer. For phase identification, glancing angle X-ray diffraction measurements was employed, while the magnetic properties of multilayer samples were measured by magneto-optical Kerr effect (MOKE) measurements. In addition, Monte Carlo simulation has been performed to correlate the ion-induced defect evolution and atomic displacements.
We report on the He+-ion induced changes in the magnetic and the structural properties of [Pt(2.5 nm) / Cr(0.8 nm) / Co(3.0 nm)]x6/Si multilayer thin films. The multilayer thin films have been irradiated at room temperature with 2 MeV He+ ions in a fluence range of 1 x 1015 to 5.5 x 1016 ions cm-2. X-ray reflectivity (XRR) measurements were performed to determine the layer thicknesses, surface and interface roughness, and the electron density of individual layer. For phase identification, glancing angle X-ray diffraction measurements was employed, while the magnetic properties of multilayer samples were measured by magneto-optical Kerr effect (MOKE) measurements. In addition, Monte Carlo simulation has been performed to correlate the ion-induced defect evolution and atomic displacements.
3. Phase formation and changes in magnetic property of Co/Cr/ Pt multilayers
3. Phase formation and changes in magnetic property of Co/Cr/ Pt multilayers
15th International Conference on Surface Modification of Materials by Ion Beams (SMMIB-15), Mumbai, India, September 30 - October 05 (2007)
15th International Conference on Surface Modification of Materials by Ion Beams (SMMIB-15), Mumbai, India, September 30 - October 05 (2007)
CoCrPt ternary alloy possesses high coercivity and good thermal stability. It is the most promising candidate for high-density perpendicular magnetic recording media because of its high coercivity and it shows drastic variation in magnetic anisotropy. However, still a lot of efforts need to be put to increase the magnetic memory from gigabyte regime to the terabyte range. Ion irradiation has been shown to be an efficient tool for tailoring the magnetic properties of layered thin film structures and to pattern magnetic media. Ion irradiation of Co/Pt and other layered structures has been shown to produce new phases and induce chemical ordering. Apart from these, extrinsic magnetic properties like magnetic anisotropy, coercivity, and magnetic exchange coupling of multilayers can also be modified using energetic ion beams.
CoCrPt ternary alloy possesses high coercivity and good thermal stability. It is the most promising candidate for high-density perpendicular magnetic recording media because of its high coercivity and it shows drastic variation in magnetic anisotropy. However, still a lot of efforts need to be put to increase the magnetic memory from gigabyte regime to the terabyte range. Ion irradiation has been shown to be an efficient tool for tailoring the magnetic properties of layered thin film structures and to pattern magnetic media. Ion irradiation of Co/Pt and other layered structures has been shown to produce new phases and induce chemical ordering. Apart from these, extrinsic magnetic properties like magnetic anisotropy, coercivity, and magnetic exchange coupling of multilayers can also be modified using energetic ion beams.
We report on the change in structural and magnetic properties of [Pt(2.5nm)/Cr(0.8nm)/Co(3.0nm)]x6/Si multilayer thin films due to 1 MeV N-ion irradiation at room temperature in the fluence range of 1 x 1012 to 1 x 1016 ions-cm-2. From glancing angle X-ray diffraction (GAXRD) studies, we see the formation of CoCrPt alloy due to mixing across the interfaces. In addition, X-ray reflectivity (XRR) measurements provide the change in the film thickness, roughness, and composition. The change in the magnetic property of the Co/Cr/Pt samples before and after irradiation were studied by magneto-optical Kerr effect (MOKE) measurements. The results are attributed to ion induced recoil mixing across the interfaces.
We report on the change in structural and magnetic properties of [Pt(2.5nm)/Cr(0.8nm)/Co(3.0nm)]x6/Si multilayer thin films due to 1 MeV N-ion irradiation at room temperature in the fluence range of 1 x 1012 to 1 x 1016 ions-cm-2. From glancing angle X-ray diffraction (GAXRD) studies, we see the formation of CoCrPt alloy due to mixing across the interfaces. In addition, X-ray reflectivity (XRR) measurements provide the change in the film thickness, roughness, and composition. The change in the magnetic property of the Co/Cr/Pt samples before and after irradiation were studied by magneto-optical Kerr effect (MOKE) measurements. The results are attributed to ion induced recoil mixing across the interfaces.
2. Effect of ion beam irradiation on magnetic and structural properties of Pt/Cr/Co multilayers
2. Effect of ion beam irradiation on magnetic and structural properties of Pt/Cr/Co multilayers
18th International Conference on Ion Beam Analysis, Hyderabad, India; September 23-28 ( 2007)
18th International Conference on Ion Beam Analysis, Hyderabad, India; September 23-28 ( 2007)
Thin mutilayer films typically involve heterogeneity both in magnetic and chemical properties and so to understand the interrelationship between the magnetic and the structural properties, thin multilayer films are very useful. CoCrPt ternary alloys are most promising candidates for high-density perpendicular magnetic recording media. They show drastic variation in magnetic anisotropy and have higher coercivity, proper coercivity squareness and low media noise. Ion beam irradiation is a very unique technique to modify several extrinsic magnetic properties of multilayer thin films like, coercivity, magnetic anisotropy, and magnetic exchange coupling in a highly localized region.
Thin mutilayer films typically involve heterogeneity both in magnetic and chemical properties and so to understand the interrelationship between the magnetic and the structural properties, thin multilayer films are very useful. CoCrPt ternary alloys are most promising candidates for high-density perpendicular magnetic recording media. They show drastic variation in magnetic anisotropy and have higher coercivity, proper coercivity squareness and low media noise. Ion beam irradiation is a very unique technique to modify several extrinsic magnetic properties of multilayer thin films like, coercivity, magnetic anisotropy, and magnetic exchange coupling in a highly localized region.
We report on the synthesis of CoCrPt ternary alloy by N-ion irradiation of [Pt(2.5nm)/Cr(0.8nm)/Co(3.0nm)]x6/Si multilayer thin films. The multilayer thin films have been irradiated at room temperature with 1 MeV N+ ions in a fluence range of 5x1015 to 2 x 1016 ions-cm-2. Atomic force microscopy (AFM), glancing angle X-ray diffraction (GIXRD), high resolution Rutherford backscattering spectrometry (HRRBS), and magneto-optical Kerr effect (MOKE) techniques have been used to study the surface morphology, phase identification, thickness and composition, and change in the magnetic properties of the Pt/Cr/Co multilayer thin films before and after irradiation. Monte Carlo simulation results for ion-induced atomic displacements will be correlated to explain the above observed effects.
We report on the synthesis of CoCrPt ternary alloy by N-ion irradiation of [Pt(2.5nm)/Cr(0.8nm)/Co(3.0nm)]x6/Si multilayer thin films. The multilayer thin films have been irradiated at room temperature with 1 MeV N+ ions in a fluence range of 5x1015 to 2 x 1016 ions-cm-2. Atomic force microscopy (AFM), glancing angle X-ray diffraction (GIXRD), high resolution Rutherford backscattering spectrometry (HRRBS), and magneto-optical Kerr effect (MOKE) techniques have been used to study the surface morphology, phase identification, thickness and composition, and change in the magnetic properties of the Pt/Cr/Co multilayer thin films before and after irradiation. Monte Carlo simulation results for ion-induced atomic displacements will be correlated to explain the above observed effects.
1. Nanomagnetism in Swift Heavy Ion Irradiated Ferromagnetic Metal/ Silicon interface
1. Nanomagnetism in Swift Heavy Ion Irradiated Ferromagnetic Metal/ Silicon interface
Indo German workshop on Synthesis and Modification of Nano-structured materials by Energetic Ion-Beams, New Delhi, India, February 20-24 (2005)
Indo German workshop on Synthesis and Modification of Nano-structured materials by Energetic Ion-Beams, New Delhi, India, February 20-24 (2005)