γ-GeSe: A New Hexagonal Polymorph from Group IV-VI Monochalcogenides

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Group IV-VI monochalcogenides possess puckered layered structures.
• Atomic configurations suggest potential for diverse polymorphs.

Purpose of the Study:

• To synthesize and characterize the first hexagonal polymorph of germanium selenide (GeSe).
• To explore the electronic and optical properties of the novel γ-GeSe phase.

Main Methods:

• Synthesis of four-atomic-thick hexagonal GeSe (γ-GeSe).
• Structural characterization using elemental analysis, electron diffraction, HRTEM, and Raman spectroscopy.
• Electrical and optical measurements.

Main Results:

• Successful synthesis and identification of hexagonal γ-GeSe.
• High electrical conductivity (3 × 10⁵ S/m) comparable to 2D semimetallic crystals.
• Direct growth on hexagonal boron nitride (h-BN) substrates demonstrated.

Conclusions:

• Hexagonal γ-GeSe is a novel 2D material with significant electrical conductivity.
• Offers a bottom-up approach for creating vertical van der Waals heterostructures.
• The unique crystal symmetry warrants further investigation into its physical properties.