γ-GeSe:a new hexagonal polymorph from group IV-VI monochalcogenides

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 γ-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 γ-GeSe exhibits high electrical conductivity of 3x10^5 S/m, which is comparable to those of other two-dimensional layered semimetallic crystals. Moreover, γ-GeSe can be directly grown on h-BN substrates, demonstrating a bottom-up approach for constructing vertical van der Waals heterostructures incorporating γ-GeSe. The newly identified crystal symmetry of γ-GeSe warrants further studies on various physical properties of γ-GeSe.

24 pages, 5 figures

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• Review of Nanolayered Post-transition Metal Monochalcogenides: Synthesis, Properties, and Applications
• First-principles Study of Phonon Lifetime and Low Lattice Thermal Conductivity of Monolayer γ-GeSe: A Comparative Study
• Versatile van der Waals Heterostructures of Gamma-GeSe with h-BN/Graphene/MoS2
• Abnormal behavior of preferred formation of cationic vacancy from the interior in γ-GeSe monolayer with the stereo-chemical antibonding lone-pair state
• Tunable bulk photovoltaic effect in strained $\gamma$-GeSe
• Controllable spin splitting in 2D Ferroelectric few-layer ${$γ}$-GeSe
• Crystalline-to-Crystalline Phase Transition between Germanium Selenide Polymorphs with High Resistance Contrast