Influence of the substrate on the diffusion coefficient and the momentum relaxation in graphene: the role of surface polar phonons

TL;DR

This study uses Monte Carlo simulations to analyze how different substrates affect the diffusion coefficient and momentum relaxation in graphene, highlighting the significant role of surface polar phonons at various electric fields.

Contribution

It provides a detailed evaluation of substrate effects on graphene's transport properties considering surface polar phonons at different electric field strengths.

Findings

Surface polar phonons reduce scattering time at low fields.

Substrate effects diminish at high fields, increasing saturation velocities.

h-BN substrate yields larger saturation velocities.

Abstract

Knowing the influence of the substrate type on the diffusion coefficient and the momentum relaxation in graphene is of great importance for the development of new device models specifically adapted to the peculiarities of this material. In this work, the influence of surface polar phonons at low and high electric fields is evaluated by means of ensemble Monte Carlo simulations for several types of substrates. The results show that at low fields surface polar phonons have a major role on reducing the scattering time, breaking the correlation of velocity fluctuations and degrading the diffusion coefficient. At high fields the differences with regard to suspended samples in terms of diffusivity and momentum relaxation tend to reduce, providing at the same time larger saturation velocities, particularly for h-BN.