Micromechanical Properties of β -Ga 2 O 3 Single Crystal By Instrumented Indentation and Scratch Tests

Gallium oxide ( β -Ga 2 O 3 ), as a representative fourth-generation semiconductor material, exhibits exceptional physical properties. However, it’s challenging to achieve high-quality wafer surfaces of β -Ga 2 O 3 crystal due to its inherent cleavability. To provide theoretical guidance for the surface machining of such cleavable materials, this study systematically investigated the micro/nano-mechanical properties of β -Ga 2 O 3 crystal by integrating first-principles calculations with nanoindentation/micro-scratch testing. First-principles calculations were employed to analyze the atomic structure and cleavage behavior of β -Ga 2 O 3 , revealing that the [GaO 6 ] octahedron is more prone to disruption than the [GaO 4 ] tetrahedron, which explains why cleavage delamination occurs on the (100)A and (100)B planes. Combining the elastic parameters obtained from first-principles calculations with nanoindentation experimental results, the following values were obtained: shear modulus ( G ) of 76 ± 13 GPa, bulk modulus ( B ) of 168.5 ± 0.5 GPa, elastic modulus ( E ) of 197.5 ± 2 8.5 GPa, hardness ( H ) of 8.5 ± 2.5 GPa, and a Poisson’s ratio ( v ) of 0.3 05 ± 0.025 . Based on nanoindentation energy analysis, linear elastic fracture mechanics (LEFM) theory, and three distinct equivalent strain energy density (ESEL) theories, the fracture toughness ( K c ) of β -Ga 2 O 3 crystal was calculated to be approximately 1.87 MPa·m 1/2 . The K c calculation method derived from LEFM theory is particularly well-suited for exfoliation-prone brittle crystalline materials.