We experimentally study the surface roughness and the lateral friction force in single-layer MoS2 crystals deposited on different substrates: SiO2, mica and hexagonal boron nitride (h-BN). Roughness and sliding friction measurements are performed by atomic force microscopy (AFM). We find a strong dependence of the MoS2 roughness on the underlying substrate material, being h-BN the substrate which better preserves the flatness of the MoS2 crystal. The lateral friction also lowers as the roughness decreases, and attains its lowest value for MoS2 flakes on h-BN substrates. However, it is still higher than for the surface of a bulk MoS2 crystal, which we attribute to the deformation of the flake due to competing tip-to-flake and flake-to-substrate interactions.
@article{arxiv.1407.2202,
title = {Single-layer MoS2 roughness and sliding friction quenching by interaction with atomically flat substrates},
author = {Jorge Quereda and Andres Castellanos-Gomez and Nicolás Agraït and Gabino Rubio-Bollinger},
journal= {arXiv preprint arXiv:1407.2202},
year = {2015}
}