title: Optical investigation of the natural electron doping in thin MoS2 films deposited on dielectric substrates.
abstract: Two-dimensional (2D) compounds provide unique building blocks for novel layered devices and hybrid photonic structures. However, large surface-to-volume ratio in thin films enhances the significance of surface interactions and charging effects requiring new understanding. Here we use micro-photoluminescence (PL) and ultrasonic force microscopy to explore the influence of the dielectric environment on optical properties of a few monolayer MoS2 films. PL spectra for MoS2 films deposited on SiO2 substrates are found to vary widely. This film-to-film variation is suppressed by additional capping of MoS2 with SiO2 and Si(x)N(y), improving mechanical coupling of MoS2 with surrounding dielectrics. We show that the observed PL non-uniformities are related to strong variation in the local electron charging of MoS2 films. In completely encapsulated films, negative charging is enhanced leading to uniform optical properties. Observed great sensitivity of optical characteristics of 2D films to surface interactions has important implications for optoelectronics applications of layered materials.
authors: Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom.
authors: D
authors: D
authors: Sercombe
authors: Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom.
authors: S
authors: S
authors: Schwarz
authors: Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom.
authors: O
authors: O
authors: Del Pozo-Zamudio
authors: 1] Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom [2] Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany.
authors: F
authors: F
authors: Liu
authors: Department of Physics, University of Lancaster, Lancaster LA1 4YB, United Kingdom.
authors: B J
authors: BJ
authors: Robinson
authors: Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom.
authors: E A
authors: EA
authors: Chekhovich
authors: Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, 142432, Russia.
authors: I I
authors: II
authors: Tartakovskii
authors: Department of Physics, University of Lancaster, Lancaster LA1 4YB, United Kingdom.
authors: O
authors: O
authors: Kolosov
authors: Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom.
authors: A I
authors: AI
authors: Tartakovskii