Talks Delivered: 28 ( 7 invited & 1 Gold Medal Honor)
Talks Delivered: 28 ( 7 invited & 1 Gold Medal Honor)
J. K. Tripathi, A. Hassanein
J. K. Tripathi, A. Hassanein
Fusion Energy Summer camp for minority students, Purdue University, July 31- Aug 4, 2023.
Fusion Energy Summer camp for minority students, Purdue University, July 31- Aug 4, 2023.
27. Performance of Plasma Facing Component Materials under Nearly Ideal Nuclear Fusion Environment: Alternate Materials to Tungsten for Harnessing the Power of the Sun on Earth
27. Performance of Plasma Facing Component Materials under Nearly Ideal Nuclear Fusion Environment: Alternate Materials to Tungsten for Harnessing the Power of the Sun on Earth
J. K. Tripathi, T. J. Novakowski, S. Gonderman, T. S. Sizyuk, A. Hassanein
J. K. Tripathi, T. J. Novakowski, S. Gonderman, T. S. Sizyuk, A. Hassanein
International e-Symposium on Plasma for Energy (ISPE) - in association with The Open University UK, The Royal Society UK, RSC local section South India, Asian African Association for Plasma Training, and Solar Energy Society of India; SRM Institute of Science & Technology, Kattankulathu, Tamil Nadu India, December 5-6, 2022 (online). (INVITED)
International e-Symposium on Plasma for Energy (ISPE) - in association with The Open University UK, The Royal Society UK, RSC local section South India, Asian African Association for Plasma Training, and Solar Energy Society of India; SRM Institute of Science & Technology, Kattankulathu, Tamil Nadu India, December 5-6, 2022 (online). (INVITED)
26. Mesoscopically Self-ordered Transition Metal Silicide Nanostructures: Electronic Growth and Magnetic Properties for Spintronics Applications
26. Mesoscopically Self-ordered Transition Metal Silicide Nanostructures: Electronic Growth and Magnetic Properties for Spintronics Applications
Jitendra Kumar Tripathi, Ilan Goldfarb
Jitendra Kumar Tripathi, Ilan Goldfarb
E Faculty development Program on Nanotechnology: Present advancement and Future Properties, AMITY Institute of Nanotechnology, AUUP, Noida, India January 18- 22, 2022. (INVITED)
E Faculty development Program on Nanotechnology: Present advancement and Future Properties, AMITY Institute of Nanotechnology, AUUP, Noida, India January 18- 22, 2022. (INVITED)
25. Tuning Mesoscopically Self-ordered Transition Metal Silicide Nanoisland Arrays for Spintronics Applications
25. Tuning Mesoscopically Self-ordered Transition Metal Silicide Nanoisland Arrays for Spintronics Applications
Jitendra Kumar Tripathi, Ilan Goldfarb
Jitendra Kumar Tripathi, Ilan Goldfarb
Research Colloquium, organized by the Department of Physics and Nanotechnology Department of Physics and Nanotechnology, SRM Institute of Science & Technology, Kattankulathu, Tamil Nadu India. for October 06, 2022 (INVITED)
Research Colloquium, organized by the Department of Physics and Nanotechnology Department of Physics and Nanotechnology, SRM Institute of Science & Technology, Kattankulathu, Tamil Nadu India. for October 06, 2022 (INVITED)
24. Performance of Plasma Facing Component Materials under extreme conditions: Alternative Materials to Tungsten for Fusion Technology on Earth (Honored by Gold Medal)
24. Performance of Plasma Facing Component Materials under extreme conditions: Alternative Materials to Tungsten for Fusion Technology on Earth (Honored by Gold Medal)
J. K. Tripathi, T. J. Novakowski, S. Gonderman, T. S. Sizyuk, A. Hassanein
J. K. Tripathi, T. J. Novakowski, S. Gonderman, T. S. Sizyuk, A. Hassanein
Research Day, SRM Institute of Science & Technology, Kattankulathu, Tamil Nadu India, March 1, 2021
Research Day, SRM Institute of Science & Technology, Kattankulathu, Tamil Nadu India, March 1, 2021
23. Tuning MoO3 nanostructures using low energy high flux He+ ion irradiation
23. 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
School of Nuclear Engineering, Center for Materials Under Extreme Environments, Purdue University, West Lafayette, IN 47907
School of Nuclear Engineering, Center for Materials Under Extreme Environments, Purdue University, West Lafayette, IN 47907
Materials Science & Technology 2017 (MS&T 17), Pittsburgh, Pennsylvania, USA; October 08 -12, 2017.
Materials Science & Technology 2017 (MS&T 17), Pittsburgh, Pennsylvania, USA; October 08 -12, 2017.
22. Experimental capabilities for advanced materials characterization at CMUXE, Purdue University (INVITED)
22. Experimental capabilities for advanced materials characterization at CMUXE, Purdue University (INVITED)
J. K. Tripathi, and A. Hassanein
J. K. Tripathi, and A. Hassanein
School of Nuclear Engineering, Center for Materials Under Extreme Environments, Purdue University, West Lafayette, IN 47907
School of Nuclear Engineering, Center for Materials Under Extreme Environments, Purdue University, West Lafayette, IN 47907
Annual Nuclear Science User Facilities (NSUF) users meeting, Idaho Falls, ID, USA, May 23 - 25, 2017
Annual Nuclear Science User Facilities (NSUF) users meeting, Idaho Falls, ID, USA, May 23 - 25, 2017
Objective: Obtain community consensus on capabilities to support ion beam irradiation of nuclear energy materials.
Objective: Obtain community consensus on capabilities to support ion beam irradiation of nuclear energy materials.
21. Performance of plasma facing component materials under high flux low energy helium ion irradiation, in extreme conditions: alternative material to tungsten for nuclear fusion applications
21. Performance of plasma facing component materials under high flux low energy helium ion irradiation, in extreme conditions: alternative material to tungsten for nuclear fusion applications
J. K. Tripathi, and A. Hassanein
J. K. Tripathi, and A. Hassanein
Homi Bhabha National Institute, Materials Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, India, November 9, 2016
Homi Bhabha National Institute, Materials Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, India, November 9, 2016
J. K. Tripathi, and A. Hassanein
J. K. Tripathi, and A. Hassanein
School of Nuclear Engineering, Center for Materials Under Extreme Environments, Purdue University, West Lafayette, IN 47907
School of Nuclear Engineering, Center for Materials Under Extreme Environments, Purdue University, West Lafayette, IN 47907
Annual Nuclear Science User Facilities (NSUF) Users Meeting, Idaho Falls, ID, USA; March 22-24, 2016
Annual Nuclear Science User Facilities (NSUF) Users Meeting, Idaho Falls, ID, USA; March 22-24, 2016
Objective: Obtain community consensus on capabilities to support ion beam irradiation of nuclear energy materials.
Objective: Obtain community consensus on capabilities to support ion beam irradiation of nuclear energy materials.
19. Tuning porosity of V2O5 by low energy He+ ion irradiation
19. Tuning porosity of V2O5 by low energy He+ ion irradiation
J. K. Tripathi, T. J. Novakowski, and A. Hassanein
J. K. Tripathi, T. J. Novakowski, and A. Hassanein
School of Nuclear Engineering, Center for Materials Under Extreme Environments, Purdue University, West Lafayette, IN 47907
School of Nuclear Engineering, Center for Materials Under Extreme Environments, Purdue University, West Lafayette, IN 47907
October 4-8, 2015
October 4-8, 2015
Porous V2O5 with nano-sized features attracted paramount interest in recent decades due to their quite high surface area, a key feature for several applications, viz., photocatalysts, electrochromic devices, sensors, supercapacitors, Li ion batteries, etc. This is because of the ease to uptake molecules or ions into its orthorhombic layered structure. We report on tuning of the porosity of V2O5 by 100 eV He+ ion irradiation with a fluence of 2.6x1024 ions m-2 having a flux of 1.2x1021 ions m-2 s-1, as a function of temperature. Surface morphology, chemical composition, and structural phase were monitored by field-emission scanning electron (FE-SEM) and atomic force (AFM) –microscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), respectively. In addition, optical-reflectivity and photoluminescence studies were also performed to determine the electronic and orbital states and to understand the mechanism involved in the recombination processes as well as information about the energy distribution of the carriers.
Porous V2O5 with nano-sized features attracted paramount interest in recent decades due to their quite high surface area, a key feature for several applications, viz., photocatalysts, electrochromic devices, sensors, supercapacitors, Li ion batteries, etc. This is because of the ease to uptake molecules or ions into its orthorhombic layered structure. We report on tuning of the porosity of V2O5 by 100 eV He+ ion irradiation with a fluence of 2.6x1024 ions m-2 having a flux of 1.2x1021 ions m-2 s-1, as a function of temperature. Surface morphology, chemical composition, and structural phase were monitored by field-emission scanning electron (FE-SEM) and atomic force (AFM) –microscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), respectively. In addition, optical-reflectivity and photoluminescence studies were also performed to determine the electronic and orbital states and to understand the mechanism involved in the recombination processes as well as information about the energy distribution of the carriers.
18. Engineering novel materials in extreme conditions for clean energy production
18. Engineering novel materials in extreme conditions for clean energy production
J. K. Tripathi
J. K. Tripathi
Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
August 31, 2015
August 31, 2015
17. Surface Science Nanostructure Group (SUSNAG) experimental capabilities at CMUXE, Purdue University
17. Surface Science Nanostructure Group (SUSNAG) experimental capabilities at CMUXE, Purdue University
J. K. Tripathi
J. K. Tripathi
Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
May 27, 2015
May 27, 2015
16. Surface Science Nanostructure Group (SUSNAG) at CMUXE: an overview
16. Surface Science Nanostructure Group (SUSNAG) at CMUXE: an overview
J. K. Tripathi
J. K. Tripathi
PIRE student workshop at Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
PIRE student workshop at Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
May 11-12, 2015
May 11-12, 2015
15. Low energy He+ ion irradiation induced surface modifications in molybdenum in extreme conditions: an alternative material for Tungsten in nuclear fusion applications
15. Low energy He+ ion irradiation induced surface modifications in molybdenum in extreme conditions: an alternative material for Tungsten in nuclear fusion applications
J. K. Tripathi
J. K. Tripathi
Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
May 13, 2015
May 13, 2015
14. Low energy He+ ion irradiation induced surface modifications on W, Mo, and Ta in extreme conditions
14. Low energy He+ ion irradiation induced surface modifications on W, Mo, and Ta in extreme conditions
J. K. Tripathi
J. K. Tripathi
Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
October 01, 2014
October 01, 2014
13. Low Energy Ar+ Ion Irradiation Induced Surface Modification in Cadmium Zinc Telluride (CdZnTe)
13. Low Energy Ar+ Ion Irradiation Induced Surface Modification in Cadmium Zinc Telluride (CdZnTe)
J. K. Tripthi, S. S. Harilal, and A. Hassanein
J. K. Tripthi, S. S. Harilal, and A. Hassanein
School of Nuclear Engineering, Center for Materials Under Extreme Environments, Purdue University, West Lafayette, IN 47907
School of Nuclear Engineering, Center for Materials Under Extreme Environments, Purdue University, West Lafayette, IN 47907
Grand Hyatt Hotel Riverwalk in San Antonio, Texas, USA
Grand Hyatt Hotel Riverwalk in San Antonio, Texas, USA
May 25-30 (2014)
May 25-30 (2014)
In recent years, paramount effort has been invested in developing a range of compound semiconductors with wide band gap and high atomic number (Z) for X- and gamma-ray detectors. Consequently, cadmium zinc telluride (Cd1-xZnxTe) has emerged as the most promising materials for these applications. It’s quite higher Z values and density ensures relatively superior stopping power compared with other conventional semiconductors and operating temperature close to room temperature. In addition, nano-semiconductor offers strong change in their energy band diagram which leads to a significant change in its properties, such as electrical (the change of free charge carriers concentration and their mobility), optical (absorption coefficient, reflectivity coefficient, and radiative recombination efficiency), mechanical and thermal properties. It has been noticed that even a very small amount of change in dopant (Zn) concentration can cause giant change in its physical and electronic properties.
In recent years, paramount effort has been invested in developing a range of compound semiconductors with wide band gap and high atomic number (Z) for X- and gamma-ray detectors. Consequently, cadmium zinc telluride (Cd1-xZnxTe) has emerged as the most promising materials for these applications. It’s quite higher Z values and density ensures relatively superior stopping power compared with other conventional semiconductors and operating temperature close to room temperature. In addition, nano-semiconductor offers strong change in their energy band diagram which leads to a significant change in its properties, such as electrical (the change of free charge carriers concentration and their mobility), optical (absorption coefficient, reflectivity coefficient, and radiative recombination efficiency), mechanical and thermal properties. It has been noticed that even a very small amount of change in dopant (Zn) concentration can cause giant change in its physical and electronic properties.
We report on modifications in structural, stoichiometry and optical properties of CdZnTe surface due surface due to 1keV Ar+ ion irradiation as function of ion fluence, using extremely high ion flux of 1.7×1017 ions cm-2 s-1. Atomic force microscopy studies show sequentially change in surface structure as a function of ion fluence, from homogeneously populated nano-hole to sub-micron sized holes which are well geometrically defined in shapes on whole sample (5mm×5mm). Using X-ray photoelectron microscopy characterizations, we observed a reduction in Zn concentration (at %). Raman and Photoluminescence studies show almost complete depletion of Te inclusions and slight red shifts due to ion irradiations, respectively. These results indicate for the possibility of large-area surface nanostructuring by ion beams which may be implemented in the fabrication of future CdZnTe-based devices.
We report on modifications in structural, stoichiometry and optical properties of CdZnTe surface due surface due to 1keV Ar+ ion irradiation as function of ion fluence, using extremely high ion flux of 1.7×1017 ions cm-2 s-1. Atomic force microscopy studies show sequentially change in surface structure as a function of ion fluence, from homogeneously populated nano-hole to sub-micron sized holes which are well geometrically defined in shapes on whole sample (5mm×5mm). Using X-ray photoelectron microscopy characterizations, we observed a reduction in Zn concentration (at %). Raman and Photoluminescence studies show almost complete depletion of Te inclusions and slight red shifts due to ion irradiations, respectively. These results indicate for the possibility of large-area surface nanostructuring by ion beams which may be implemented in the fabrication of future CdZnTe-based devices.
12. Self-organized ordering in Metal Silicides on Si (111)
12. Self-organized ordering in Metal Silicides on Si (111)
J. K. Tripathi
J. K. Tripathi
Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
Center for Materials Under Extreme Environments (CMUXE), School of Nuclear Engineering, Purdue University, USA
May 15, 2013
May 15, 2013
11. Superparamagnetism in self-ordered Iron-Silicide nanostructures on vicinal Si (111) surface
11. Superparamagnetism in self-ordered Iron-Silicide nanostructures on vicinal Si (111) surface
Jitendra Kumar Tripathi, Magnus Garbrecht, Wayen D. Kaplan, Gil Markovich and Ilan Goldfarb
Jitendra Kumar Tripathi, Magnus Garbrecht, Wayen D. Kaplan, Gil Markovich and Ilan Goldfarb
15th Israel Materials Engineering Conference (IMEC-15)
15th Israel Materials Engineering Conference (IMEC-15)
Le Meridien hotel at the Dead Sea, Israel
Le Meridien hotel at the Dead Sea, Israel
February 28-March 1 (2012)
February 28-March 1 (2012)
Iron-silicides may exhibit metallic, magnetic, or semiconducting behavior, as a function of stoichiometry, and hence show great potential of optical, electronic, and spintronic devices. Bottom-up self-assembled and self-organized fabrication of iron-silicide nanostructures may result in additional, quantum-size effects. In this work, we grew iron-silicide nanostructures by solid-phase epitaxy, namely room-temperature deposition of Fe onto atomically clean vicinal Si(111) substrates, followed by elevated-temperature anneals to promote Fe-Si reaction. We observed transformation of the initially flat silicide layer into a discrete bimodal distribution of nanoislands decorating the Si(111) step edges in a self-ordered fashion, upon annealing up to 550 degrees Celsius. Our scanning tunneling microscopy (STM), high-resolution transmission electron microscopy (HR-TEM), and x-ray photoelectron spectroscopy (XPS) indicated metallic α-FeSi2 phase embedded with small fraction of elemental Fe. SQUID magnetometry showed superparamagnetism most likely linked to the self-ordered nanostructures.
Iron-silicides may exhibit metallic, magnetic, or semiconducting behavior, as a function of stoichiometry, and hence show great potential of optical, electronic, and spintronic devices. Bottom-up self-assembled and self-organized fabrication of iron-silicide nanostructures may result in additional, quantum-size effects. In this work, we grew iron-silicide nanostructures by solid-phase epitaxy, namely room-temperature deposition of Fe onto atomically clean vicinal Si(111) substrates, followed by elevated-temperature anneals to promote Fe-Si reaction. We observed transformation of the initially flat silicide layer into a discrete bimodal distribution of nanoislands decorating the Si(111) step edges in a self-ordered fashion, upon annealing up to 550 degrees Celsius. Our scanning tunneling microscopy (STM), high-resolution transmission electron microscopy (HR-TEM), and x-ray photoelectron spectroscopy (XPS) indicated metallic α-FeSi2 phase embedded with small fraction of elemental Fe. SQUID magnetometry showed superparamagnetism most likely linked to the self-ordered nanostructures.
10. Coverage-dependent self-organized ordering in Metal Silicides
10. Coverage-dependent self-organized ordering in Metal Silicides
J. K. Tripathi, M. Levinshtein and I. Goldfarb
J. K. Tripathi, M. Levinshtein and I. Goldfarb
International Conference on Multifunctional Material-2010 (ICMM-2010)
International Conference on Multifunctional Material-2010 (ICMM-2010)
Department of Physics, Banaras Hindu University, Varanasi, India
Department of Physics, Banaras Hindu University, Varanasi, India
December 6-9 (2010)
December 6-9 (2010)
J.K.Tripathi, S. Manor, E. Roizin, M. Levinshtein and I. Goldfarb
J.K.Tripathi, S. Manor, E. Roizin, M. Levinshtein and I. Goldfarb
14th Israel Materials Engineering Conference (IMEC-14)
14th Israel Materials Engineering Conference (IMEC-14)
Tel Aviv University, Ramat Aviv, Israel
Tel Aviv University, Ramat Aviv, Israel
December 13-14 (2009)
December 13-14 (2009)
Growth of metals on silicon substrates has been attracting significant interest for quite some time now, because heterostructure interfaces, and metal/silicon interfaces in particular, are of paramount importance to many applications in contemporary and future device technology. Recent findings of lead and silver islands on Si, with single - or a few “magic” - heights, came as a surprise, since apriori a continuous distribution of island heights was to be expected. The explanation has been that those magic heights act as quantum wells (QW’s), and hence are stabilized by the electron energy. More specifically, QW states in stable islands are energetically distant from the Fermi level. Up until now, such stabilization of flat overgrowth morphology by a reduction of the overall electron energy in a QW (hence termed “electronic growth”), has been observed exclusively in heteroepitaxy of simple metals only, e.g., lead and silver. However in this work, based on scanning tunneling microscopy (STM) and spectroscopy (STS) measurements of heteroepitaxial island height distributions and density of states (DOS), respectively, we demonstrate first evidence of the above "electronic growth" in titanium- and cobalt-silicide heterostructures on Si(111). Since these silicides are certainly not “simple metals” in terms of their crystal and electronic structure, these results imply that the "electronic growth" mechanism may apply to a broader class of heterosystems. The importance of “electronic growth” is in the fact that it provides a possibility of growing single height islands or layers by self-assembly even in large-mismatch systems. In the particular case of the above silicides, the immediate advantage stems from them being technologically important materials for VLSI due to their low resistivity, resistance to electromigration, and the ability to self-align.
Growth of metals on silicon substrates has been attracting significant interest for quite some time now, because heterostructure interfaces, and metal/silicon interfaces in particular, are of paramount importance to many applications in contemporary and future device technology. Recent findings of lead and silver islands on Si, with single - or a few “magic” - heights, came as a surprise, since apriori a continuous distribution of island heights was to be expected. The explanation has been that those magic heights act as quantum wells (QW’s), and hence are stabilized by the electron energy. More specifically, QW states in stable islands are energetically distant from the Fermi level. Up until now, such stabilization of flat overgrowth morphology by a reduction of the overall electron energy in a QW (hence termed “electronic growth”), has been observed exclusively in heteroepitaxy of simple metals only, e.g., lead and silver. However in this work, based on scanning tunneling microscopy (STM) and spectroscopy (STS) measurements of heteroepitaxial island height distributions and density of states (DOS), respectively, we demonstrate first evidence of the above "electronic growth" in titanium- and cobalt-silicide heterostructures on Si(111). Since these silicides are certainly not “simple metals” in terms of their crystal and electronic structure, these results imply that the "electronic growth" mechanism may apply to a broader class of heterosystems. The importance of “electronic growth” is in the fact that it provides a possibility of growing single height islands or layers by self-assembly even in large-mismatch systems. In the particular case of the above silicides, the immediate advantage stems from them being technologically important materials for VLSI due to their low resistivity, resistance to electromigration, and the ability to self-align.
08. Tailoring magnetic properties by ion irradiation
08. Tailoring magnetic properties by ion irradiation
J. K. Tripathi
J. K. Tripathi
Dept. Cond. Matter and Mater. Science, Tata Institute of Fundamental Research (TIFR), Mumbai, India
Dept. Cond. Matter and Mater. Science, Tata Institute of Fundamental Research (TIFR), Mumbai, India
November 7-9 (2008)
November 7-9 (2008)
In recent years, it has been shown that magnetic properties of ultra-thin magnetic multilayers depend strongly on the surface and interface structure, chemical composition, crystallinity, and grain sizes and their distributions. In general, all these structural properties can be tailored by ion irradiation. In addition, it has been shown that the magnetic properties can also be tailored by ion irradiation. In this seminar, I shall talk on tailoring the magnetic properties of Pt/Cr/Co multilayers by ion irradiation.
In recent years, it has been shown that magnetic properties of ultra-thin magnetic multilayers depend strongly on the surface and interface structure, chemical composition, crystallinity, and grain sizes and their distributions. In general, all these structural properties can be tailored by ion irradiation. In addition, it has been shown that the magnetic properties can also be tailored by ion irradiation. In this seminar, I shall talk on tailoring the magnetic properties of Pt/Cr/Co multilayers by ion irradiation.
07. Tailoring magnetic properties of ultrathin Pt/Cr/Co multilayers by ion irradiation (INVITED)
07. Tailoring magnetic properties of ultrathin Pt/Cr/Co multilayers by ion irradiation (INVITED)
J. K. Tripathi
J. K. Tripathi
International conference and Humboldt-kolleg on structural characterization of materials relevant to nanotechnology, biomedical and Geobiology
International conference and Humboldt-kolleg on structural characterization of materials relevant to nanotechnology, biomedical and Geobiology
Banaras Hindu University, Varanasi, India
Banaras Hindu University, Varanasi, India
November 7-9 (2008)
November 7-9 (2008)
06. MeV ion irradiation of Pt/Cr/Co multilayers: Correlation of structural and magnetic properties, (INVITED)
06. MeV ion irradiation of Pt/Cr/Co multilayers: Correlation of structural and magnetic properties, (INVITED)
J. K. Tripathi, A. Gupta, and T. Som
J. K. Tripathi, A. Gupta, and T. Som
Seminar-cum-Workshop on Materials Characterization and surface modification in research and Industry using Ion Accelerators (MCIA)
Seminar-cum-Workshop on Materials Characterization and surface modification in research and Industry using Ion Accelerators (MCIA)
Institute of Physics, Bhubaneswar, India
Institute of Physics, Bhubaneswar, India
April 03 (2008)
April 03 (2008)
In recent years, it has been shown that magnetic properties of ultrathin magnetic multilayers depend strongly on the surface and interface structure, chemical composition, crystallinity, and grain sizes and their distributions. In general, all these structural properties can be tuned by ion irradiation. 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.
In recent years, it has been shown that magnetic properties of ultrathin magnetic multilayers depend strongly on the surface and interface structure, chemical composition, crystallinity, and grain sizes and their distributions. In general, all these structural properties can be tuned by ion irradiation. 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.
In this talk, I shall discuss on MeV ion irradiation of Pt/Cr/Co multilayer and subsequent changes in the structural and the magnetic properties. Ion-induced defect evolution and atomic displacements would be correlated the ion induced change in the structural and the magnetic properties of the multilayer.
In this talk, I shall discuss on MeV ion irradiation of Pt/Cr/Co multilayer and subsequent changes in the structural and the magnetic properties. Ion-induced defect evolution and atomic displacements would be correlated the ion induced change in the structural and the magnetic properties of the multilayer.
05.Tuning magnetic property of Pt/Cr/Co multilayer by Ion irradiation
05.Tuning magnetic property of Pt/Cr/Co multilayer by Ion irradiation
J. K. Tripathi
J. K. Tripathi
Institute of Physics, Bhubaneswar, India
Institute of Physics, Bhubaneswar, India
January 07 (2008)
January 07 (2008)
In recent years, it has been shown that magnetic properties of ultrathin magnetic multilayers depend strongly on the surface and interface structure, chemical composition, crystallinity, and grain sizes and their distributions. In general, all these structural properties can be tuned by ion irradiation. In addition, it has been shown that the magnetic properties can also be tuned by ion irradiation. In this seminar, I shall talk on tuning the magnetic properties of ultrathin magnetic multilayers by ion irradiation.
In recent years, it has been shown that magnetic properties of ultrathin magnetic multilayers depend strongly on the surface and interface structure, chemical composition, crystallinity, and grain sizes and their distributions. In general, all these structural properties can be tuned by ion irradiation. In addition, it has been shown that the magnetic properties can also be tuned by ion irradiation. In this seminar, I shall talk on tuning the magnetic properties of ultrathin magnetic multilayers by ion irradiation.
04. A Study on Cr doped GaN DMS system
04. A Study on Cr doped GaN DMS system
J. K. Tripathi, D. Kanjilal and T. Som
J. K. Tripathi, D. Kanjilal and T. Som
Workshop on Materials Science and Atomic/Molecular Physics Experiments using the Low Energy Ion Beam Facility
Workshop on Materials Science and Atomic/Molecular Physics Experiments using the Low Energy Ion Beam Facility
Inter-University Accelerator Centre, New Delhi, India
Inter-University Accelerator Centre, New Delhi, India
February 21 (2007)
February 21 (2007)
Spintronics has attracted much attention recently. The spintronics devices are being explored in which electronic spin shall carry the information instead of electronic charge. The ferromagnetic (FM) / semiconductor (SC) hybrid structures are expected to find applications for such devices. But in a diffusive transport regime, successful spin injection occurs only for two conditions: Either the conductivities of FM and SC are closely matched or FM is 100% polarized. No FM metal has been realized at present, which meets either of these two conditions. Since all current electronic devices operate in the diffusive transport regime, these results appear to preclude FM metals as viable candidate for spin contacts in such devices. Further, it is interesting to note that diluted magnetic semiconductors (DMS) satisfy both criteria at low temperatures and high magnetic fields. It provides excellent electrical spin injection in another semiconductor providing electron population with a spin polarization 80%. Recently, it has been found that Cr-doped GaN based DMS shows ferromagnetic ordering near-room-temperature.
Spintronics has attracted much attention recently. The spintronics devices are being explored in which electronic spin shall carry the information instead of electronic charge. The ferromagnetic (FM) / semiconductor (SC) hybrid structures are expected to find applications for such devices. But in a diffusive transport regime, successful spin injection occurs only for two conditions: Either the conductivities of FM and SC are closely matched or FM is 100% polarized. No FM metal has been realized at present, which meets either of these two conditions. Since all current electronic devices operate in the diffusive transport regime, these results appear to preclude FM metals as viable candidate for spin contacts in such devices. Further, it is interesting to note that diluted magnetic semiconductors (DMS) satisfy both criteria at low temperatures and high magnetic fields. It provides excellent electrical spin injection in another semiconductor providing electron population with a spin polarization 80%. Recently, it has been found that Cr-doped GaN based DMS shows ferromagnetic ordering near-room-temperature.
In view of the above, we plan to synthesize GaN based DMS system, viz. GaN:Cr using ion implantation technique. It is known that GaN is a wide band gap (Eg=3.45eV) semiconductor having tremendous applications in optoelectronics. On the other hand, advantages of using the ion implantation technique are manifold: (i) high spatial selectivity, (ii) precise control of the dopant density, and (iii) far-from-equilibrium processing of materials. Recently, it has been observed that Cr doped GaN shows extremely high Curie temperature (>900 K), which prompts us to take up this project. In this study, we propose to use 100-200 keV Cr ions at different temperatures and fluences (1×1016 – 1×1017 ions cm-2). The samples will be characterized later by X-ray diffraction (XRD), photoluminescence (PL), micro-Raman, and MOKE measurements.
In view of the above, we plan to synthesize GaN based DMS system, viz. GaN:Cr using ion implantation technique. It is known that GaN is a wide band gap (Eg=3.45eV) semiconductor having tremendous applications in optoelectronics. On the other hand, advantages of using the ion implantation technique are manifold: (i) high spatial selectivity, (ii) precise control of the dopant density, and (iii) far-from-equilibrium processing of materials. Recently, it has been observed that Cr doped GaN shows extremely high Curie temperature (>900 K), which prompts us to take up this project. In this study, we propose to use 100-200 keV Cr ions at different temperatures and fluences (1×1016 – 1×1017 ions cm-2). The samples will be characterized later by X-ray diffraction (XRD), photoluminescence (PL), micro-Raman, and MOKE measurements.
03. Spintronic Behaviour in Swift Heavy Ion Irradiated Fe/Si devices
03. Spintronic Behaviour in Swift Heavy Ion Irradiated Fe/Si devices
J. K. Tripathi, P.C. Srivastava
J. K. Tripathi, P.C. Srivastava
Workshop on Functional Oxide Materials
Workshop on Functional Oxide Materials
Inter-University Accelerator Centre, New Delhi, India
Inter-University Accelerator Centre, New Delhi, India
September 25 (2006)
September 25 (2006)
Fe/Si interface devices have been fabricated by electron beam evaporation technique. The above fabricated devices have also been irradiated from swift ( ~100 MeV ) heavy Fe7+ ions . After irradiation it is found that there is an occurrence of strong interfacial intermixing to result the nano granular magnetic silicides of Fe5Si3 . These nano granular magnetic silicides show a magnetic behaviour of coupled nano grains . Such a behaviour is characterized by a blocking temperature and a hysteresis . The blocking temperature of ~ 50 K could be estimated from ZFC and FC measurements on the irradiated devices. From MFM ( Magnetic Force Microscopy ), magnetic domain like features could be observed .
Fe/Si interface devices have been fabricated by electron beam evaporation technique. The above fabricated devices have also been irradiated from swift ( ~100 MeV ) heavy Fe7+ ions . After irradiation it is found that there is an occurrence of strong interfacial intermixing to result the nano granular magnetic silicides of Fe5Si3 . These nano granular magnetic silicides show a magnetic behaviour of coupled nano grains . Such a behaviour is characterized by a blocking temperature and a hysteresis . The blocking temperature of ~ 50 K could be estimated from ZFC and FC measurements on the irradiated devices. From MFM ( Magnetic Force Microscopy ), magnetic domain like features could be observed .
Electronic transport study show a temperature independent and nearly a linear I-V behaviour at lower voltages , suggesting a tunnel mechanism of the electronic flow across the devices ( of Fe/Si ). Magnetotransport and magnetization studies suggest a spin controlled transport across the tunnel barrier between the magnetically coupled nano granular magnetic silicides ( of Fe5Si3 ) separated by nanometer scaled silicon tunneling barrier .
Electronic transport study show a temperature independent and nearly a linear I-V behaviour at lower voltages , suggesting a tunnel mechanism of the electronic flow across the devices ( of Fe/Si ). Magnetotransport and magnetization studies suggest a spin controlled transport across the tunnel barrier between the magnetically coupled nano granular magnetic silicides ( of Fe5Si3 ) separated by nanometer scaled silicon tunneling barrier .
A GMR of 2400% has been found in the irradiated Fe/Si devices, which is unique observation and seem to be observed by us for the first time. The observed GMR has been understood in the realm of spin dependent interfacial scattering.
A GMR of 2400% has been found in the irradiated Fe/Si devices, which is unique observation and seem to be observed by us for the first time. The observed GMR has been understood in the realm of spin dependent interfacial scattering.
02. A Study on Magnetic Metal/Silicon Interface Devices; with and without Swift Heavy Ion Irradiation
02. A Study on Magnetic Metal/Silicon Interface Devices; with and without Swift Heavy Ion Irradiation
J. K. Tripathi
J. K. Tripathi
Department of Physics, Banaras Hindu University, Varanasi, India
Department of Physics, Banaras Hindu University, Varanasi, India
February 28 (2006)
February 28 (2006)
01. Nano Granular Magnetic silicide phase formation due to Swift Heavy ion irradiation in Fe/Si structures,
01. Nano Granular Magnetic silicide phase formation due to Swift Heavy ion irradiation in Fe/Si structures,
J. K. Tripathi
J. K. Tripathi
Inter-University Accelerator Centre, New Delhi, India
Inter-University Accelerator Centre, New Delhi, India
June 05 (2003)
June 05 (2003)