Quality heterostructures from two dimensional crystals unstable in air by their assembly in inert atmosphere

TL;DR

This paper presents a method for fabricating air-sensitive two-dimensional crystal heterostructures in an inert atmosphere, enabling stable, high-quality devices from materials previously unstable in air, such as black phosphorus and niobium diselenide.

Contribution

The authors introduce an inert atmosphere assembly technique for air-sensitive 2D crystals, allowing stable device fabrication and expanding research possibilities.

Findings

Devices from black phosphorus and NbSe2 are stable in ambient conditions.

NbSe2 remains superconducting at monolayer thickness.

Phosphorene devices exhibit Landau quantization at high mobilities.

Abstract

Many layered materials can be cleaved down to individual atomic planes, similar to graphene, but only a small minority of them are stable under ambient conditions. The rest reacts and decomposes in air, which has severely hindered their investigation and possible uses. Here we introduce a remedial approach based on cleavage, transfer, alignment and encapsulation of air-sensitive crystals, all inside a controlled inert atmosphere. To illustrate the technology, we choose two archetypal two-dimensional crystals unstable in air: black phosphorus and niobium diselenide. Our field-effect devices made from their monolayers are conductive and fully stable under ambient conditions, in contrast to the counterparts processed in air. NbSe2 remains superconducting down to the monolayer thickness. Starting with a trilayer, phosphorene devices reach sufficiently high mobilities to exhibit Landau quantization. The approach offers a venue to significantly expand the range of experimentally accessible two-dimensional crystals and their heterostructures.