Controllable growth of γ-GeSe microflakes by vapor phase deposition via rapid cooling strategy

Abstract

γ-GeSe has recently emerged as a promising material for electronics and optoelectronics due to its unique band structure and excellent electrical properties. However, controllable growth of γ-GeSe remains a significant challenge. In this work, the controllable growth of γ-GeSe microflakes (MFs) on a mica substrate was reported by vapor phase deposition via a rapid cooling strategy. The screw dislocation-driven growth behavior is confirmed based on systematic characterizations. Our experimental results demonstrate that the stress induced during the rapid cooling process is critical for the controllable synthesis of γ-GeSe MFs and corresponding growth mechanism was proposed. Our work provides a new experimental strategy for the controlled growth of γ-GeSe MFs, which is beneficial for constructing GeSe-based nanoelectronic and optoelectronic devices.

Unveiling the distinctive mechanical and thermal properties of γ-GeSe

“…Conversely, γ-GeSe features a distinct hexagonal crystal structure, characterized by individual layers that are four-atom-thick (Fig. 1 a), as verified recently [ 24 , 29 ]. The hexagonal symmetry of γ-GeSe suggests that it should exhibit isotropic physical properties within its plane.…”

“…GeSe is a unique group-IV monochalcogenide, which exhibits various types of stable polymorphs at room temperature [ 23 – 26 ]. Recently, γ-GeSe has been recognized as a stable monochalcogenide featuring a distinctive intralayer structure, characterized by a Se-Ge-Ge-Se quadruple atomic sequence [ 24 , 27 – 29 ]. Intriguingly, its inter-atomic bonding configuration deviates from the conventional 8 -N rule, resembling instead the bonding pattern found in crystals exhibiting so-called metavalent bonding [ 27 , 30 ].…”

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

“…26 The synthesis of γ-GeSe, with its layered hexagonal structure and four-atom-thick layer units, has been reported recently. 27,28 γ-GeSe has an indirect bandgap of 0.33 eV and a direct bandgap of 0.54 eV, as calculated by the GW approximation. 27 Experimentally, the electrical conductivity γ-GeSe is significantly high (∼10 6 S m −1 ) due to the formation of Ge vacancies and resulted p-type doping.…”

“…29 The high electrical conductivity and the unique bonding configuration of γ-GeSe make it a promising material for energy storage, ferroelectric and thermoelectric applications. 29–35 However, previous reports on γ-GeSe synthesis have suffered owing to the formation of mixed products (such as α-GeSe or GeSe 2 ), 27,28 and the large-scale selective growth of γ-GeSe has not been accomplished. Additionally, Ge–Se binary compounds exhibit various types of structures, such as Ge 4 Se 9 , which may complicate the synthesis of γ-GeSe.…”