Effects of forming gas annealing on the doping of monolayer MoS2 crystals

Abstract

Here we report the effects of forming gas (5% H2 in N2) annealing on the doping behavior of mechanically-exfoliated, natural n-type MoS2 monolayers. Although the fabricated MoS2 transistors exhibited an enhanced device performance because of the reduced contact resistance after annealing at 200 °C for 2 h, the corresponding Raman and photoluminescence spectra suggested that the forming gas annealing suppressed the n-type doping behavior of MoS2. X-ray photoelectron spectroscopy and Kelvin probe force microscopy measurements consistently suggested a downward movement of the Fermi level of the MoS2 monolayers after the forming gas annealing. These results demonstrate the importance of optimizing the process conditions during the forming gas annealing for the fabrication of MoS2 transistors and devices based on transition metal dichalcogenides.