Engineering high quality graphene superlattices via ion milled ultra-thin etching masks

TL;DR

This paper introduces a novel nanofabrication method using focused ion beam milling to create ultra-fine, high-quality graphene superlattices with a 16 nm pitch, enabling advanced quantum material studies.

Contribution

It presents a new technique for patterning sub-20 nm structures with minimal proximity effects, surpassing current electron beam lithography capabilities.

Findings

Achieved 16 nm pattern pitch in graphene superlattices

Demonstrated high-quality superlattice properties via electronic transport

Observed a rich Hofstadter butterfly spectrum in the fabricated structures

Abstract

Nanofabrication research pursues the miniaturization of patterned feature size. In the current state of the art, micron scale areas can be patterned with features down to ~ 30 nm pitch using electron beam lithography. Our work demonstrates a new nanofabrication technique which allows patterning periodic structures with a pitch down to 16 nm. It is based on focused ion beam milling of suspended membranes, with minimal proximity effects typical to electron beam lithography. The membranes are then transferred and used as hard etching masks. We benchmark our technique by engineering a superlattice potential in single layer graphene using a thin graphite patterned gate electrode. Our electronic transport characterization shows high quality superlattice properties and a rich Hofstadter butterfly spectrum. Our technique opens the path towards the realization of very short period superlattices in 2D materials, comparable to those in natural moire systems, but with the ability to control lattice symmetries and strength. This can pave the way for a versatile solid-state quantum simulator platform and the study of correlated electron phases.