Ultimate charge transport regimes in doping-controlled graphene laminates: phonon-assisted processes revealed by the linear magnetoresistance

TL;DR

This paper investigates charge transport in doping-controlled graphene laminates, revealing phonon-assisted processes as key factors influencing conductivity and mobility, with implications for printed electronics and thermoelectric applications.

Contribution

It demonstrates how thermolysis of aromatic intercalants enhances mobility and doping control, and identifies phonon-assisted tunneling as a main limiting factor for conductivity.

Findings

High intra-flake mobility observed via linear magnetoresistance

Phonon-assisted tunneling dominates at temperatures above 20K

Thermoelectric sensitivity of around 50 μV/K achieved in graphene thermocouples

Abstract

Understanding and controlling the electrical properties of solution-processed 2D materials is key to further printed electronics progress. Here we demonstrate that the thermolysis of the aromatic intercalants utilized in nanosheet exfoliation for graphene laminates opens the route to achieving high intrinsic mobility and simultaneously controlling doping type ($n$- and $p$-) and concentration over a wide range. We establish that the intra-flake mobility is high by observing a linear magnetoresistance of such solution-processed graphene laminates and using it to devolve the inter-flake tunneling and intra-layer magnetotransport. Consequently, we determine the temperature dependences of the inter- and intra-layer characteristics, which both appear to be dominated by phonon-assisted processes at temperature $T>$20 Kelvin. In particular, we identify the efficiency of phonon-assisted tunneling as the main limiting factor for electrical conductivity in graphene laminates at room temperature. We also demonstrate a thermoelectric sensitivity of around 50 ${\mu}$V K$^{-1}$ in a solution-processed metal-free graphene-based thermocouple.