Investigation of MoS2 growth on GaN/sapphire substrate using molecular beam epitaxy

• Wafer-scale growth of MoS 2 monolayers on GaN/Sapphire Substrates by MBE. • Initial formation of triangular-shaped MoS 2 flakes/domains. • Coexistence of 1 T and 1H phases with distinct layer interactions. The growth of two-dimensional molybdenum disulphide (MoS 2 ) layers on Gallium Nitride/Sapphire (GaN/Al 2 O 3 ) substrates using molecular beam epitaxy (MBE) growth technique has been investigated. We show that optimized conditions at a substrate temperature around 700 °C lead to full surface coverage of MoS 2 on GaN. The growth proceeds through the initial formation of triangular-shaped MoS 2 flakes/domains on the GaN surface. Raman spectroscopy and high-resolution scanning transmission electron microscopy reveal the formation at the wafer-scale of a MoS 2 monolayer and few bilayers. A closer analysis of regions with two MoS 2 layers reveals the coexistence of both 1 T and 1H phases, showing strong bonds between the top layer of GaN and the first MoS 2 layer, and van der Waals interactions between the first and second MoS 2 layers.