Electrical transport and low-temperature scanning tunneling microscopy of microsoldered graphene

TL;DR

This study uses microsoldering to investigate electrical transport and low-temperature STM of graphene, revealing doping effects, minimal contamination, and non-linear phenomena related to phonons and Landau levels.

Contribution

It introduces a microsoldering technique for graphene, showing its effects on doping, contamination, and electronic properties with detailed STM and transport analysis.

Findings

PMMA causes doping up to 3.8x10^12 1/cm^2

Microsoldered graphene is contamination-free

Observation of phonon gap closing and Landau level features

Abstract

Using the recently developed technique of microsoldering, we perform a systematic transport study of the influence of PMMA on graphene flakes revealing a doping effect of up to 3.8x10^12 1/cm^2, but a negligible influence on mobility and gate voltage induced hysteresis. Moreover, we show that the microsoldered graphene is free of contamination and exhibits a very similar intrinsic rippling as has been found for lithographically contacted flakes. Finally, we demonstrate a current induced closing of the previously found phonon gap appearing in scanning tunneling spectroscopy experiments, strongly non-linear features at higher bias probably caused by vibrations of the flake and a B-field induced double peak attributed to the 0.Landau level of graphene.