Point contacts in encapsulated graphene

TL;DR

This paper introduces a new method for creating small, inner point contacts in encapsulated graphene, enabling advanced electronic and quantum Hall experiments with low contact resistance.

Contribution

A novel dry-stacking technique for fabricating sub-100 nm inner point contacts in hBN-encapsulated graphene structures.

Findings

Contact resistances of 0.5-1.5 kΩ per contact

Qualitative agreement with electrostatic models

Observation of insulating behavior in quantum Hall regime

Abstract

We present a novel method to establish inner point contacts on hexagonal boron nitride (hBN) encapsulated graphene heterostructures with dimensions as small as 100 nm by pre-patterning the top-hBN in a separate step prior to dry-stacking. 2 and 4-terminal field effect measurements between different lead combinations are in qualitative agreement with an electrostatic model assuming pointlike contacts. The measured contact resistances are 0.5-1.5 k$\Omega$ per contact, which is quite low for such small contacts. By applying a perpendicular magnetic fields, an insulating behaviour in the quantum Hall regime was observed, as expected for inner contacts. The fabricated contacts are compatible with high mobility graphene structures and open up the field for the realization of several electron optical proposals.