Four-terminal magneto-transport in graphene p-n junctions created by spatially selective doping

TL;DR

This study demonstrates a method for creating graphene p-n junctions via chemical doping that preserves mobility, enabling observation of quantum Hall effects and quantized resistances in four-terminal measurements.

Contribution

It introduces a chemical doping technique for graphene p-n junctions that maintains high mobility and enables quantum Hall measurements with quantized resistances.

Findings

Chemical doping does not reduce graphene mobility.

Spatially selective doping can be achieved with patterned PMMA.

Quantized resistances consistent with theory are observed.

Abstract

In this paper we describe a graphene p-n junction created by chemical doping. We find that chemical doping does not reduce mobility in contrast to top-gating. The preparation technique has been developed from systematic studies about influences on the initial doping of freshly prepared graphene. We investigated the removal of adsorbates by vacuum treatment, annealing and compensation doping using NH3. Hysteretic behavior is observed in the electric field effect due to dipolar adsorbates like water and NH3. Finally we demonstrate spatially selective doping of graphene using patterned PMMA. 4-terminal transport measurements of the p-n devices reveal edge channel mixing in the quantum hall regime. Quantized resistances of h/e^2, h/3e^2 and h/15e^2 can be observed as expected from theory.