A first-principles study of van der Waals interactions and lattice mismatch at MoS2/metal interfaces

TL;DR

This study uses first-principles density functional theory to analyze van der Waals interactions and lattice mismatch effects at MoS2/metal interfaces, revealing how different metals influence electronic properties and Fermi level pinning.

Contribution

It provides detailed insights into the electronic interactions and interface states of MoS2 on various metals, emphasizing the importance of van der Waals forces in accurate modeling.

Findings

MoS2 chemisorbs on Ti, strongly perturbing electronic structure

MoS2 physisorbs on Au with minimal electronic disturbance

Interface states pin Fermi level below conduction band in some metals

Abstract

We explore the adsorption of MoS2 on a range of metal substrates by means of first-principles density functional theory calculations. Including van der Waals forces in the density functional is essential to capture the interaction between MoS2 and a metal surface, and obtain reliable interface potential steps and Schottky barriers. Special care is taken to construct interface structures that have a mismatch between the MoS2 and the metal lattices of <1%. MoS2 is chemisorbed on the early transition metal Ti, which leads to a strong perturbation of its (electronic) structure and a pinning of the Fermi level 0.54 eV below the MoS2 conduction band due to interface states. MoS2 is physisorbed on Au, where the bonding hardly perturbs the electronic structure. The bonding of MoS2 on other metals lies between these two extreme cases, with interface interactions for the late 3d transition metals Co, Ni, Cu and the simple metal Mg that are somewhat stronger than for the late 4d/5d transition metals Pd, Ag, Pt and the simple metal Al. Even a weak interaction, such as in the case of Al, gives interface states, however, with energies inside the MoS2 band gap, which pin the Fermi level below the conduction band.