Research

Terahertz Biosensor

Metamaterial and plasmonic devices operating in the terahertz (THz) frequency range turned out to be one of the ideal candidates for highly sensitive and selective microbial sensing. The target substance includes fungi, bacteria, viruses, proteins, and DNAs.

Terahertz thermal curve analysis for label-free identification of pathogens

Nature Communications 13, 3470 (2022); DOI: 10.1038/s41467-022-31137-2

S. W. Jun, Y. H. Ahn*

Identifying different types of microorganisms with terahertz spectroscopy

Biomedical Optics Express 11, 406 (2020); DOI: 10.1364/BOE.376584

S. A. Yoon, S. H. Cha, S. W. Jun, S. J. Park, J.-Y. Park, S. Lee, H. S. Kim, Y. H. Ahn*

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 with Novel Functional Materials

We are developing hybrid devices with tunable quantum states by incorporating lead halide perovskites into metamaterials.

Phonon-Polaritons in Lead Halide Perovskite Film Hybridized with THz Metamaterials

Nano Letters 20, 6690 (2020); DOI: 10.1021/acs.nanolett.0c02572

H. S. Kim, N. Y. Ha, J.-Y. Park, S. Lee, D.-S. Kim, Y. H. Ahn*

Mechanical Control of Polaritonic States in Lead Halide Perovskite Phonons Strongly Coupled in THz Microcavity

J. Phys. Chem. Lett. 14, 10318 (2023); DOI: 10.1021/acs.jpclett.3c02717

H. S. Kim, A. A. Khan, J.-Y. Park, S. Lee, Y. H. Ahn*

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*

We also 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.

Graphene Oxides as Epsilon-Near-Zero Platforms Operating in Terahertz Frequency Range

Laser & Photonics Reviews, 2300726 (2023); DOI: 10.1002/lpor.202300726

S. W. Jun, J. H. Yim, J.-Y. Park, S. Lee, Y. H. Ahn*

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

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 signals originate from local electric fields, their position, intensity, and polarity provide the localized electronic information originating from metal contacts, defects, inhomogeneities, junctions, and interfaces.

- In-plane mixed-dimensional 2D/2D/1D MoS2 /MoTe2 /Mo6Te6 heterostructures for low contact resistance optoelectronics

Chemical Engineering Journal 468, 143678 (2023); DOI: 10.1016/j.cej.2023.143678

H. Kim, Y. C. Kim, Y. H. Ahn*, Y. Yoo*

- 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

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.

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

Evaluation of Transport Parameters in MoS2/Graphene Junction Devices Fabricated by Chemical Vapor Deposition

ACS Appl. Mater. Interfaces 10, 5771 (2018); DOI: 10.1021/acsami.7b16177

Y. C. Kim, V. T. Ngyuen, S. Lee, J.-Y Park*, Y. H. Ahn*

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.

- 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