报 告 人：Prof. Dong-Wook Kim
工作单位：Ewha Womans University
Dr. Dong-Wook Kim received his Ph.D in Physics from Seoul National University. He had been selected as the Senior Researcher in Samsung Advanced Inst. of Technology in the period of 2001-2005. From 2005 to 2008, he worked as the research professor and assistant professor at POSTECH and Hanyang University respectively. From 2008 he has moved to Ewha Womans University as an assistant Professor of physics, and he has been promoted as associate Professor in 2012. Now, he is the Dean of Department of Physics, in Ewha Womans University. His Research Interests include Nanoscopic characterizations using scanning probe microscopy, Metal-semiconductor hybrid nanostructures for optoelectronic applications, and Epitaxial oxide heterostructures: growth and physical characterizations. Dr. Dong-Wook Kim has been selected as the Chair of Division of Sensor & Energy, Korea Society of Optoelectronics, and he has also been selected as the Editorial Board Member of Scientific Reports and Editorial Board Member of Current Applied Physics from 2015. He has published more than 200 refereed journal papers in these research fields, with his H-index as 27.
Metal and semiconductor nanostructures exhibit unique optical characteristics, including enhanced absorption/scattering cross-sections and strong light confinement near the surface at the resonance. It is very important to understand and control the interplay among photons, surface plasmons, and charges in such nanostructures, in order to realize novel nanostructure-based optoelectronic devices. In this talk, I will introduce three research achievements in my group, relevant to real-space mapping of surface photovoltage (SPV), i.e., changes in the surface potential under illumination, using Kelvin probe force microscopy.
We fabricated ZnO/Ag nanogratings, which could couple surface plasmon polaritons (SPPs) with photons, resulting in significant increase of the photoluminescence intensity . SPVof the nanogratings was larger than that of the planar counterpart when SPPs were excited. As another signature of the SPP excitation, the SPV relaxation time of the nanogratings clearly depended on the wavelength and polarization. We also fabricated Si nanopillar (NP) arrays coated with organic semiconductor P3HT layers . SPV on the NP top was much larger than that on a planar sample, indicating generation of numerous carriers within the NPs. Such distinct SPV behaviors could be attributed to strongly confined light in the nanostrucutres via thegeometric Mie-like resonance.Recently, we could visualize conversion of near-infrared incident light to visible light by Gd3+-doped β-NaYF4:Yb3+/Er3+ upconversion nanorods (UCNs) . The SPV measurements successfully confirmed the formation of charge carriers in P3HT layers coated on the UCNs.