In situ X-ray photoelectron spectroscopy study: effect of inert Ar sputter etching on the core-level spectra of the CVD-grown tri-layer MoS2 thin films

Atomically thin molybdenum disulfide (MoS2) thin films are a promising avenue of investigation due to its potential applications in modern nanoscale electronic devices. In this work, we present a systematic investigation of the effect of in situ argon-ion sputter etching on the core-level X-ray photoelectron spectroscopy (XPS) of the chemical vapor-deposited MoS2 thin films. Raman spectroscopy of the MoS2 reveals that the thin films are tri-layer samples. Photoluminescence spectrum of the tri-layer MoS2 consists of A- and B-exciton emission peaks at 1.85 and 1.99 eV, respectively. The core-level XPS spectra of the Mo-3d and S-2p levels of the tri-layer MoS2 were investigated for various in situ sputter etch time. The as-grown and 6 s sputter-etched MoS2 sample exhibited Mo-3d spin-orbit doublets corresponding to + 4 oxidation state of Mo. For the sputter etch time beyond 40 s, the sample exhibited + 6 oxidation states of molybdenum suggesting the presence of thin molybdenum oxide at the interface between MoS2 and sapphire. We have also observed mid oxidation states like Mo5+, which is attributed to the argon-ion sputter etch-induced sulfur-deficient mixed S-Mo-O and sub-stoichiometric phases. (C) The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2021.

Automated summary

This study systematically investigated the effect of in situ argon-ion sputter etching on the core-level X-ray photoelectron spectroscopy of chemical vapor-deposited MoS2 thin films. The results showed that the chemical composition and oxidation states of the MoS2 thin films changed with different etch times, leading to sulfur deficiency and formation of molybdenum oxide at the interface between MoS2 and sapphire.