Growth behavior during metalorganic chemical vapor deposition of MoS2 using di-tert-butyl sulfide as organic sulfur precursor

Abstract

Metalorganic chemical vapor deposition is a promising synthesis technique for two-dimensional materials such as MoS2. In this study, we controlled the growth mode of MoS2 on SiO2 using Mo(CO)6 and di-tert-butyl sulfide as precursors by adjusting the process conditions. The growth was directed from amorphous deposition at 400 ∘C and 500 ∘C, to crystalline MoS2 at 600 ∘C and higher. From 750 ∘C, not only MoS2 grains were deposited, but Mo metal nuclei were also formed during the process. An enhancement of the grain size was achieved by increasing the S/Mo precursor ratio. A more effective method to enlarge the grains and to lower the number density of crystals was to anneal the SiO2 substrate in Ar atmosphere prior to deposition. The reduced number density suggested that the pretreatment increased the diffusion length of Mo adatom species on the surface. Furthermore, addition of H2 to the N2 carrier gas had two effects on the growth mode, without altering the amount of deposited Mo. On one hand, due to a higher fraction of H2 in the carrier gas, the grain size slightly increased, and on the other hand, a change towards Mo metal deposition was observed. Control of the process conditions offers the opportunity to deposit large MoS2 grains without co-depositing Mo metal.