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.
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.
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.
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.
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.