Dielectric Thickness Dependence of Carrier Mobility in Graphene with HfO2 Top Dielectric

TL;DR

This study examines how the thickness of HfO2 dielectric layers affects carrier mobility in graphene, revealing that mobility drops during initial dielectric deposition and is mainly limited by nearby fixed charged impurities rather than phonon scattering.

Contribution

It provides new insights into the dielectric thickness dependence of carrier mobility in graphene and identifies fixed charged impurities as the primary mobility-limiting factor.

Findings

Mobility decreases during the first 2-4 nm of dielectric deposition.

Mobility remains constant for thicker dielectric layers.

Temperature has a weak effect on mobility, indicating phonon scattering is not dominant.

Abstract

We investigate the carrier mobility in mono- and bi-layer graphene with a top HfO2 dielectric, as a function of the HfO2 film thickness and temperature. The results show that the carrier mobility decreases during the deposition of the first 2-4 nm of top dielectric and remains constant for thicker layers. The carrier mobility shows a relatively weak dependence on temperature indicating that phonon scattering does not play a dominant role in controlling the carrier mobility. The data strongly suggest that fixed charged impurities located in close proximity to the graphene are responsible for the mobility degradation.