Al₂O₃ as a suitable substrate and a dielectric layer for n -layer MoS₂

Sapphire (α-Al₂O₃) is a common substrate for the growth of single- to few-layer MoS₂ films, and amorphous aluminium oxide serves as a high-κ dielectric gate oxide for MoS₂ based transistors. Using density-functional theory calculations with a van der Waals functional, we investigate the structural, energetic, and electronic properties of n-layer MoS₂ (n=1and 3) on the α-Al₂O₃ (0001) surface. Our results show that the sapphire stabilizes single-layer and tri-layer MoS₂, while having a negligible effect on the structure, band gap, and electron effective masses of MoS₂. This combination of a strong energetic stabilization and weak perturbation of the electronic properties shows that α-Al₂O₃ can serve as an ideal substrate for depositing ultra-thin MoS₂ layers and can also serve as a passivation or gate-oxide layer for MoS₂ based devices.