Substrate Effects on Growth Dynamics of WTe2 Thin films

Abstract

Synthesis of transition metal dichalcogenides (TMDCs) has been achieved through the direct conversion of metal and metal-oxide films, demonstrating the ability to grow large area thin films with uniform thickness on a variety of substrates and direct control over the growth orientation (horizontal vs vertical) of the TMDC layers. However, the synthesized TMDC films often exhibit small grains and are more defective than their bulk counterparts. This is especially true for 2D telluride films due to the low reactivity between tellurium and transition metals such as W and Mo. In this work, the substrate interactions is examined for WTe2 converted from amorphous WOx thin films grown by atomic layer deposition, on c-plane sapphire and SiO2 through tellurization at high temperatures. Similar to TMDC telluride MoTe2, the formation of monolayer WTe2 on sapphire is observed, but not on SiO2. However, due to decreased diffusion of W on sapphire compared to Mo, the formation of WTe2 flakes instead of continuous films is observed, providing insight into the role of the specific transition metal during the direct synthesis of TMDC telluride films.