Accessing the transport properties of graphene and its multi-layers at high carrier density

TL;DR

This study investigates high carrier density transport in mono-, bi-, and trilayer graphene using electric-double-layer transistors, revealing saturation in monolayer and non-monotonic behavior in multilayers, with implications for future applications.

Contribution

It provides a systematic comparison of high-density transport in different graphene layers using ion-gated transistors, highlighting band-filling effects and quantum capacitance changes.

Findings

Monolayer graphene conductivity saturates at high carrier density.

Bi- and trilayer graphene exhibit non-monotonic conductivity due to higher energy band filling.

Ion-gated graphene demonstrates robustness suitable for future device applications.

Abstract

We present a comparative study of high carrier density transport in mono-, bi-, and trilayer graphene using electric-double-layer transistors to continuously tune the carrier density up to values exceeding 10^{14} cm^{-2}. Whereas in monolayer the conductivity saturates, in bi- and trilayer flling of the higher energy bands is observed to cause a non-monotonic behavior of the conductivity, and a large increase in the quantum capacitance. These systematic trends not only show how the intrinsic high-density transport properties of graphene can be accessed by field-effect, but also demonstrate the robustness of ion-gated graphene, which is crucial for possible future applications.