First-principles study on surface passivation of the GaN substrate during the synthesis of MoS2 monolayer using MOCVD

Abstract

GaN has been investigated as a substrate for synthesizing MoS2 monolayer (ML), which are promising semiconductor materials due to their similarity in lattice structure. In this study, surface passivation of the GaN substrate, when synthesizing MoS2 ML using metal organic chemical vapor deposition (MOCVD), is predicted by first-principles calculations. Firstly, H, S, O, and OH are selected as candidates for passivating adsorbents based on the synthetic environment and the XPS measurement results. Calculating the surface formation energy when each adsorbent passivates the GaN surface, at the experimental condition of 750 K and 1.6 Torr, the GaN surface is passivated by OH. In this case, 3 OH are located on the H3 site per 4 surface Ga. However, the GaN surface is passivated by S beyond 1000 K. In this case, 3 S are located on the H3 site per 8 surface Ga. Furthermore, it is difficult to distinguish which of OH or S passivate the GaN surface by only measuring the van der Waals (vdW) distance between the GaN substrate and MoS2 ML.