Impact of reduced graphene oxide on MoS2 grown by sulfurization of sputtered MoO3 and Mo precursor films

Abstract

Monolayer molybdenum disulfide (MoS2), a two dimensional semiconducting dichalcogenide material with a bandgap of 1.8–1.9 eV, has demonstrated promise for future use in field effect transistors and optoelectronics. Various approaches have been used for MoS2 processing, the most common being chemical vapor deposition. During chemical vapor deposition, precursors such as Mo, MoO3, and MoCl5 have been used to form a vapor reaction with sulfur, resulting in thin films of MoS2. Currently, MoO3 ribbons and powder, and MoCl5 powder have been used. However, the use of ribbons and powder makes it difficult to grow large area-continuous films. Sputtering of Mo is an approach that has demonstrated continuous MoS2 film growth. In this paper, the authors compare the structural properties of MoS2 grown by sulfurization of pulse vapor deposited MoO3 and Mo precursor films. In addition, they have studied the effects that reduced graphene oxide (rGO) has on MoS2 structure. Reports show that rGO increases MoS2 grain growth during powder vaporization. Herein, the authors report a grain size increase for MoS2 when rGO was used during sulfurization of both sputtered Mo and MoO3 precursors. In addition, our transmission electron microscopy results show a more uniform and continuous film growth for the MoS2 films produced from Mo when compared to the films produced from MoO3. Atomic force microscopy images further confirm this uniform and continuous film growth when Mo precursor was used. Finally, x-ray photoelectron spectroscopy results show that the MoS2 films produced using both precursors were stoichiometric and had about 7–8 layers in thickness, and that there was a slight improvement in stoichiometry when rGO was used.