Horizontal to Vertical Transition of MoS2 grown by CVD on Mo studied by Spectroscopic Ellipsometry

Dresden

Congreso; 8th edition of Graphene Conference series; 2018

Graphene Conference

The control in the orientation of MoS2 layers with respect to the growing substrate is of upmost importance in MoS2 applications. Horizontally aligned MoS2 layers are preferred for microelectronic devices, whereas vertically aligned MoS2 layers are much useful for the hydrogen evolution reaction and energy storage. Fast sulfurization of metal-seeded substrates has been used to grow vertically standing MoS2 nanosheets. The layers grow until the thin Mo film (5-25 nm) is consumed. However, the growth of MoS2 films on thicker Mo foils has not been investigated yet. In this work we investigate structural transitions as a function of temperature for CVD grown MoS2 on specular polished molybdenum surfaces exposed to sulphur gas. The thickness of the MoS2 films obtained from the elllipsometric spectra have an abrupt transition around 800oC in agreement with the topography of SEM images which show a change from smooth films to structures with vertically aligned layers.