Germanium Diselenide Ribbons with Orthorhombic Crystal Structure.

Sutter, Eli; French, Jacob S; Sutter, Peter · Nano Lett · 2022

basic_science · Level V

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Abstract

Many materials are known to exist in several stable polymorphs, but synthesis only provides access to a subset. This situation is exemplified by the dichalcogenide semiconductor GeSe<sub>2</sub>. Besides the amorphous form, which attracted intense interest, crystalline GeSe<sub>2</sub> in the bulk and in nanostructures such as flakes and nanobelts invariably adopts the 2D/layered monoclinic β-phase. Hence, the properties of other polymorphs such as the orthorhombic 3D GeSe<sub>2</sub> phase remain unknown. Here, we report the high-yield synthesis of orthorhombic GeSe<sub>2</sub> nanoribbons by GeSe/Se vapor transport over Au catalysts. Access to air-stable monocrystalline, single-phase ribbons enabled investigating the properties of orthorhombic GeSe<sub>2</sub> including its characteristic Raman spectrum. Optical absorption on ensembles and cathodoluminescence spectroscopy on individual ribbons show a wide bandgap and intense band-to-band emission in the visible, with a broad sub-bandgap emission tail. Our results establish orthorhombic GeSe<sub>2</sub> ribbons as a promising wide-bandgap semiconductor nanostructure for applications in optoelectronics and energy conversion.