Layer Number Determination and Thickness-dependent Properties of Graphene Grown on SiC

TL;DR

This paper investigates how the electronic properties of graphene grown on SiC depend on the number of layers, revealing layer-dependent mobility and proposing SEM contrast as a rapid characterization method.

Contribution

It provides new insights into layer-dependent electronic behavior and introduces SEM contrast as an efficient tool for layer number determination in graphene on SiC.

Findings

Carrier mobility increases with layer thickness due to reduced substrate scattering.

Transition in mobility behavior occurs around 2 layers.

SEM contrast effectively determines layer number with higher throughput.

Abstract

The electronic properties of few-layer graphene grown on the carbon-face of silicon carbide (SiC) are found to be strongly dependent on the number of layers. The carrier mobility is larger in thicker graphene because substrate-related scattering is reduced in the higher layers. The carrier density dependence of the mobility is qualitatively different in thin and thick graphene, with the transition occurring at about 2 layers. The mobility increases with carrier density in thick graphene, similar to multi-layer graphene exfoliated from natural graphite, suggesting that the individual layers are still electrically coupled in spite of reports recording non-Bernal stacking order in C-face grown graphene. The Hall coefficient peak value is reduced in thick graphene due to the increased density of states. A reliable and rapid characterization tool for the layer number is therefore highly desirable. To date, AFM height determination and Raman scattering are typically used since the optical contrast of graphene on SiC is weak. However, both methods suffer from low throughput. We show that the scanning electron microscopy (SEM) contrast can give similar results with much higher throughput.