Abstract

Large-scale integration of MoS$_2$ in electronic devices requires the development of reliable and cost-effective deposition processes, leading to uniform MoS$_2$ layers on a wafer scale. Here we report on the detailed study of the heterogeneous vapor-solid reaction between a pre-deposited molybdenum solid film and sulfur vapor, thus resulting in a controlled growth of MoS$_2$ films onto SiO$_2$/Si substrates with a tunable thickness and cm$^2$-scale uniformity. Based on Raman spectroscopy and photoluminescence, we show that the degree of crystallinity in the MoS$_2$ layers is dictated by the deposition temperature and thickness. In particular, the MoS$_2$ structural disorder observed at low temperature (<750 $^{\circ}$C) and low thickness (two layers) evolves to a more ordered crystalline structure at high temperature (1000 $^{\circ}$C) and high thickness (four layers). From an atomic force microscopy investigation prior to and after sulfurization, this parametrical dependence is associated with the inherent granularity of the MoS$_2$ nanosheet that is inherited by the pristine morphology of the pre-deposited Mo film. This work paves the way to a closer control of the synthesis of wafer-scale and atomically thin MoS$_2$, potentially extendable to other transition metal dichalcogenides and hence targeting massive and high-volume production for electronic device manufacturing.