122nd General Meeting of the KCS

Type Oral Presentation
Area Oral Presentation for Young Scholars in Physical Chemistry
Room No. Room 324A
Time THU 09:00-:
Code PHYS.O-1
Subject Charge transfer at WS2-SiO2 interface studied with in-situ photoluminescence imaging
Authors Haneul Kang, Sunmin Ryu*
Department of Chemistry, Pohang University of Science and Technology, Korea
Abstract Understanding charge transfer (CT) between two-dimensional (2D) crystals and molecules is important for fundamental research and future applications of 2D material systems. Despite recent surge on this research subject, however, the roles of the interface formed by supporting substrates and their surfaces have not been investigated. In particular, ambient water may form a medium on hydrophilic surfaces for electrochemical reactions with oxygen in the air.[1] In this work, we investigated the CT interaction of single-layer WS2 with the proposed redox couple of O2/H2O serving as a hole dopant.[1] Photoluminescence (PL) and Raman spectra obtained for WS2/SiO2 in a gas-controlled optical cell served as an indicator of charge density and showed that hole doping is mediated by O2 and H2O. Much reduced CT on hexagonal boron nitride substrates suggested a conclusive role of interface between WS2 and hydrophilic SiO2 substrate. Wide-field PL imaging was exploited to investigate spatial inhomogeneity and anisotropy. We will further discuss detailed photophysics of charged excitons (trions) and possible roles of defects in the observed CT reactions. References [1] V. Chakrapani, J. C. Angus, A. B. Anderson, S. D. Wolter, B. R. Stoner, G. U. Sumanasekera, Science 318, 1424 (2007)
E-mail neul1231@postech.ac.kr