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 MoS₂. In this study, we controlled the growth mode of MoS₂on SiO₂using Mo(CO)₆and 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 MoS₂at 600 °C and higher. From 750 °C, not only MoS₂grains 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 SiO₂substrate 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 H₂to the N₂carrier gas had two effects on the growth mode, without altering the amount of deposited Mo. On one hand, due to a higher fraction of H₂in 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 MoS₂grains without co-depositing Mo metal.