{\gamma}-GeSe:a new hexagonal polymorph from group IV-VI monochalcogenides

TL;DR

This paper reports the synthesis and characterization of a novel hexagonal polymorph of GeSe, expanding the family of group IV-VI monochalcogenides with potential applications in layered heterostructures.

Contribution

The first synthesis and structural confirmation of the hexagonal {3}-GeSe polymorph, previously only predicted, with detailed characterization and demonstration of its growth on h-BN substrates.

Findings

{33}-GeSe exhibits high electrical conductivity of 3x10^5 S/m.

{33}-GeSe can be grown directly on h-BN substrates.

The new polymorph has a different crystal symmetry warranting further physical property studies.

Abstract

The family of group IV-VI monochalcogenides has an atomically puckered layered structure, and their atomic bond configuration suggests the possibility for the realization of various polymorphs. Here, we report the synthesis of the first hexagonal polymorph from the family of group IV-VI monochalcogenides, which is conventionally orthorhombic. Recently predicted four-atomic-thick hexagonal GeSe, so-called {\gamma}-GeSe, is synthesized and clearly identified by complementary structural characterizations, including elemental analysis, electron diffraction, high-resolution transmission electron microscopy imaging, and polarized Raman spectroscopy. The electrical and optical measurements indicate that synthesized {\gamma}-GeSe exhibits high electrical conductivity of 3x10^5 S/m, which is comparable to those of other two-dimensional layered semimetallic crystals. Moreover, {\gamma}-GeSe can be directly grown on h-BN substrates, demonstrating a bottom-up approach for constructing vertical van der Waals heterostructures incorporating {\gamma}-GeSe. The newly identified crystal symmetry of {\gamma}-GeSe warrants further studies on various physical properties of {\gamma}-GeSe.