Unveiling the distinctive mechanical and thermal properties of γ-GeSe.

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 ([Formula: see text]) 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[Formula: see text]7.5 GPa as determined by optical interferometry and 109.4[Formula: see text]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 [Formula: see text] 0.4 WmK and a total thermal conductivity of 7.5 [Formula: see text] 0.4 WmK in the in-plane direction at room temperature. The notably high [Formula: see text] ratio in γ-GeSe, compared to other layered materials, underscores its distinctive structural and dynamic characteristics.