Growth behavior during metalorganic chemical vapor deposition of MoS ₂ using di-tert-butyl sulfide as organic sulfur precursor

Metalorganic chemical vapor deposition (MOCVD) is a promising synthesis technique for two-dimensional materials such as MoS 2 . In this study, we controlled the growth mode of MoS 2 on SiO 2 using Mo(CO) 6 and di-tert-butyl sulfide (DTBS) as precursors by adjusting the process conditions. The growth was directed from amorphous deposition at 400 and 500 °C, to crystalline MoS 2 at 600 °C and higher. From 750 °C, not only MoS 2 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 SiO 2 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 H 2 to the N 2 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 H 2 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 MoS 2 grains without co-depositing Mo metal.