Research
Scanning Photocurrent Microscopy on Nanoscale Devices
Scanning photocurrent microscopy (SPCM) uses a focused light beam as a local excitation source to generate a photocurrent and maps the measured current signal as a function of position in a non-contact and non-destructive manner. Since the SPCM signal originates from local electric fields, the position, intensity, and the shape of the signal provide detailed information regarding the presence of metal contacts, local defects, inhomogeneities, junctions, and interfaces.
Related articles:
Electronic Band Alignment at Complex Oxide Interfaces Measured by Scanning Photocurrent Microscopy
Scientific Reports 7, 3824 (2017); DOI: 10.1038/s41598-017-04265-9
J. H. Yoon, H. J. Jung, J. T. Hong, J. Y. Park, S. Lee, S. W. Lee, Y. H. Ahn
Imaging surface charge distribution near carbon nanotube device in aqueous environments
Appl. Phys. Lett. 105, 223101 (2014); DOI: 10.1063/1.4902401; featured (cover) article
J. K. Park, B. H. Son, J. Y. Park, S. Lee, Y. H. Ahn
High-speed scanning photocurrent imaging techniques on nanoscale devices
Curr. Appl. Phys.13 2076 (2013); DOI: 10.1016/j.cap.2013.08.019
J. K. Park, B. H. Son, J. Y. Park, S. Lee, Y. H. Ahn
Imaging of Photocurrent Generation and Collection in Single-Layer Graphene
Nano Lett. 9, 1742 (2009)
J. Park, Y. H. Ahn, C. Ruiz-Vargas
Photocurrent Imaging of p-n Junctions in Ambipolar Carbon Nanotube Transistors
Nano Lett. 7, 3320 (2007)
Y. H. Ahn, A. W. Tsen, B. Kim, Y. W. Park, J. Park
Solar Cell Characterization
The carrier diffusion lengths in semiconductor electrode layers of solar cells can be determined by using scanning photocurrent microscopy. We found a strong correlation between the carrier diffusion length and the cell efficiency, which proved that improvement in the diffusion length is the crucial factors for optimizing device performance. Our work will provide an important guideline for optimizing various contemporary and future photovoltaic devices based on the nanoscale materials and structures.
Related articles:
Crystallization Kinetics of Lead Halide Perovskite Film Monitored by In Situ Terahertz Spectroscopy
J. Phys. Chem. Lett. 8, 401 (2017); DOI: 10.1021/acs.jpclett.6b02691
S. J. Park, A. R. Kim, J. T. Hong, J. Y. Park, S. Lee, Y. H. Ahn
Diffusion Length in Nanoporous Photoelectrodes of Dye-Sensitized Solar Cells under Operating Conditions Measured by Photocurrent Microscopy
J. Phys. Chem. Lett. 3, 3632 (2012); DOI: 10.1021/jz301751j
J.-K. Park, J.-C. Kang, S. Y. Kim, B. H. Son, J.-Y. Park, S. Lee, Y. H. Ahn
Diffusion Length in Nanoporous TiO2 Films under Above-Band-Gap Illumination
AIP. Adv. 4, 067106 (2014); DOI: 10.1063/1.4881875
J. D. Park, B. H. Son, J. K. Park, S. Y. Kim, J. Y. Park, S. Lee, Y. H. Ahn
Ultrafast Scanning Photocurrent Microscopy
Ultrafast Scanning Photocurrent Microscopy, which is combined scanning photocurrent microscopy and femtosecond (10-15 second) pump-probe optical techniques, can be used for visualization of the charge carrier movement inside the working semiconductor devices. This information will provide an important guideline to fabricate high-speed electronic and optoelectronic devices.
Related article:
Imaging Ultrafast Carrier Transport in Nanoscale Field-Effect Transistors
ACS Nano 8, 11361 (2014); DOI: 10.1021/nn5042619; SPIE newsroom
B. H. Son, J. K. Park, J. T. Hong, J. Y. Park, S. Lee, Y. H. Ahn
Terahertz Biosensor
Nowadays, we are researching the terahertz (THz) metamaterial and plasmonic devices to realize a highly sensitive and selective microbial biosensor operating in the terahertz frequency. We optimize the various THz biosensors by changing their parameters through Finite Difference Time Domain (FDTD) simulation and fabricate the optimized biosensor by using our various fabrication facilities. With optimized THz biosensor, we are trying to detect various biological substances such as fungi, bacteria, virus, protein, DNA and ETC.
Related Article:
Detection of microorganisms using terahertz metamaterials
Scientific Reports 4, 4988 (2014); DOI: 10.1038/srep04988
S. J. Park, J. T. Hong, S. J. Choi, H. S. Kim, W. K. Park, S. T. Han, J. Y. Park, S. Lee, D. S. Kim, Y. H. Ahn
Sensing viruses using terahertz nano-gap metamaterials
Biomedical Optics Express 8, 3551 (2017); DOI: 10.1364/BOE.8.003551
S. J. Park, S. H. Cha, G. A. Shin, Y. H. Ahn
Dielectric constant measurements of thin films and liquids using terahertz metamaterials
RSC Adv. 6, 69381 (2016); DOI: 10.1039/c6ra11777e
S. J. Park, S. A. N. Yoon, Y. H. Ahn
Terahertz metamaterial sensing on polystyrene microbeads: shape dependence
Opt. Mater. Express 5, 2150 (2015); DOI: 10.1364/OME.5.002150
S. J. Park, S. W. Jun, A. R. Kim, Y. H. Ahn
Sensitive detection of yeast using terahertz slot antennas
Opt. Express 22, 30467 (2014); DOI: 10.1364/OE.22.030467
S. J. Park, B. H. Son, S. J. Choi, H. S. Kim, Y. H. Ahn
Suspended single-walled carbon nanotube fluidic sensors
Nanoscale 7, 15421 (2015); DOI: 10.1039/C5NR03215F
B. H. Son, J. Y. Park, S. Lee, Y. H. Ahn
Terahertz Metamaterials and Plasmonics Using Low-Dimensional Materials
We use the highly conductive nanomaterial films (such as carbon nanotube, graphene, silver nanowire) as a novel platform for THz optical devices such as polarizers, metamaterials, and plasmonic devices.
Related Article:
Terahertz slot antenna devices fabricated on silver nanowire network films
Opt. Mater. Express 7, 1679 (2017); DOI: 10.1364/OME.7.001679
J. T. Hong, S. J. Park, J-. Y. Park, S. Lee, Y. H. Ahn
UV-induced terahertz wave modulation in freestanding ZnO nanowire films
Opt. Mater. Express 6, 3751 (2016); DOI: 10.1364/OME.6.003751
J. T. Hong, J. Y. Park, S. Lee, Y. H. Ahn
Dielectric Constant Engineering of Single-Walled Carbon Nanotube Films for Metamaterials and Plasmonic Devices
J. Phys. Chem. Lett. 4, 3950 (2013); DOI: 10.1021/jz4020053
J. T. Hong, D. J. Park, J. H. Yim, J. K. Park, J. Y. Park, S. Lee, Y. H. Ahn
Terahertz conductivity of reduced graphene oxide films
Opt. Express 21, 7633 (2013); DOI: 10.1364/OE.21.007633
J. T. Hong, K. M. Lee, B. H. Son, S. J. Park, D. J. Park, J. Y. Park, S. Lee, and Y. H. Ahn
Terahertz Wave Applications of Single-Walled Carbon Nanotube Films with High Shielding Effectiveness
Appl. Phys. Express 5, 015102 (2012)
J. T. Hong, D. J. Park, J. Y. Moon, S. B. Choi, J. K. Park, F. Rotermund, J. Y. Park, S. Lee, Y. H. Ahn