Effect of Substrate on Sulfur Vacancy Defect-Mediated Photoluminescence in Two-Dimensional MoS<sub>2</sub>
Yiru Zhu, Zhepeng Zhang, Ye Wang, Soumya Sarkar, Yang Li, Han Yan, Larissa Ishibe-Veiga, Anita Bagri, Ziwei Jeffrey Yang, Hugh Ramsden, Goki Eda, Robert L. Z. Hoye, Yan Wang, Manish Chhowalla
Abstract
High Resolution Image Download MS PowerPoint Slide Chalcogen vacancy defects in monolayer transition metal dichalcogenides form in-gap states that can trap excitons, leading to defect-mediated photoluminescence (PL) emission. Here, we show that room-temperature (RT, 300 K) PL from sulfur vacancies in defective monolayer MoS 2 is sensitive to doping from dielectric substrates such as SiO 2 and HfO 2 . The defect-mediated PL is observed for monolayer MoS 2 on untreated HfO 2 but is quenched on untreated SiO 2, which is attributed to electron doping of MoS 2 on SiO 2 . Electron doping of MoS 2 is confirmed by Raman and synchrotron X-ray photoelectron spectroscopy. Annealing of the SiO 2 substrate modifies its surface states, which is reflected in the recovery of the defect-mediated PL emission. The role of substrate-induced doping on sulfur vacancy-mediated PL is further supported by gate-dependent PL measurements. Our results suggest that excess electrons fill the defect energy states from sulfur vacancies in MoS 2, reducing the probability of photoexcited carrier occupation and subsequent defect-mediated emission.