Unveiling the Distinctive Mechanical and Thermal Properties of γ-GeSe

Abstract γ-GeSe is a newly identified polymorph among group-IV monochalcogenides, characterized by a distinctive interatomic bonding configuration. Despite its promising applications in electrical and thermal domains, the experimental verification of its mechanical and thermal properties remains unreported. Here, we experimentally characterize the in-plane Young’s modulus (E) and thermal conductivity (\(κ\)) of γ-GeSe. The mechanical vibrational modes of freestanding γ-GeSe flakes are measured using optical interferometry. Nano-indentation via atomic force microscopy is also conducted to induce mechanical deformation and to extract the E. Comparison with finite-element simulations reveals that the E is 97.3\(±\)7.5 GPa as determined by optical interferometry and 109.4\(±\)13.5 GPa as established through the nano-indentation method. Additionally, optothermal Raman spectroscopy reveals that γ-GeSe has a lattice thermal conductivity of 2.3\(±\)0.4 Wm⁻¹K⁻¹ and a total thermal conductivity of 7.5\(±\)0.4 Wm⁻¹K⁻¹ in the in-plane direction at room temperature. The notably high \(E/κ\) ratio in γ-GeSe, compared to other layered materials, underscores its distinctive structural and dynamic characteristics.