Semiconductor to metal transition in two-dimensional gold and its van der Waals heterostack with graphene

TL;DR

This paper reports the synthesis of a large-area two-dimensional gold layer within a van der Waals heterostructure with graphene, revealing a tunable semiconductor-to-metal transition with potential spintronic applications.

Contribution

It demonstrates the first large-area synthesis of 2D gold stabilized between SiC and graphene and uncovers a novel, tunable semiconductor to metal transition in 2D gold layers.

Findings

2D gold is a semiconductor with a valence band 50 meV below Fermi level.

The heterostructure exhibits a 225 meV spin-orbit splitting.

Tuning gold at the interface induces a semiconductor to metal transition.

Abstract

The synthesis of transition metals in a two-dimensional (2D) fashion has attracted growing attention for both fundamental and application-oriented investigations, such as 2D magnetism, nanoplasmonics and non-linear optics. However, the large-area synthesis of this class of materials in a single-layer form poses non-trivial difficulties. Here we present the synthesis of a large-area 2D gold layer, stabilized in between silicon carbide and monolayer (ML) graphene. We show that the 2D-Au ML is a semiconductor with the valence band maximum 50 meV below the Fermi level. The graphene and gold layers are largely non-interacting, thereby defining a novel class of van der Waals heterostructure. The 2D-Au bands, exhibit a 225 meV spin-orbit splitting along the {\Gamma K} direction, making it appealing for spin-related applications. By tuning the amount of gold at the SiC/graphene interface, we induce a semiconductor to metal transition in the 2D-Au, which was never observed before and hosts great interest for fundamental physics.