Understanding the growth mechanisms of γ-GeSe for polymorph-selective large-area deposition

Understanding the growth mechanisms of a newly discovered polymorphic material and achieving large-scale selective growth is critical for accurate material characterization and application. Post-transition metal monochalcogenides, including Ge chalcogenides, are known to exhibit various polymorphic configurations, and selectively growing a target metastable polymorph is challenging. This study delves into the growth mechanisms and polymorph-selective growth methods of γ-phase germanium selenide (GeSe), a recently identified hexagonal polymorph. The role of the Au catalyst in the vapor-liquid-solid synthesis of γ-GeSe is investigated in detail via crystallographic and morphological investigations of growth products as a function of Au catalyst size. Azimuthally-aligned γ-GeSe flakes grow more efficiently and selectively on boron nitride and graphite templates, indicating the importance of the growth substrate. Chemical-vapor-deposited graphene-covered substrates allow for large-area growth of γ-GeSe, leading to practical applications.