Investigation of the nano and micromechanical performance of β-Ga2O3 epitaxial films on sapphire using nanoindentation

Beta-phase gallium oxide (β-Ga2O3) has attracted considerable attention because of its excellent properties as one of the emerging semiconductor materials. However, not only the fabrication of high quality β-Ga2O3 thin films on heterogeneous substrates is challenging, but there is also a lack of research pertaining to their mechanical properties. In this work, the mechanical properties of β-Ga2O3 epitaxial films of varying thicknesses on c-plane sapphire substrates fabricated via plasma enhanced chemical vapor deposition were investigated through nanoindentation and nano-scratch experiments. The β-Ga2O3 hetero-epitaxial thin films exhibit preferential orientation growth along the (−201) plane when deposited on the c-plane sapphire substrate. The elastic modulus, hardness, and fracture toughness of β-Ga2O3 films grown on sapphire substrates are 249.1±14.1 GPa, 18.7±0.9 GPa, and 1.822 MPa⋅m1/2, respectively. The elastic-plastic behavior of β-Ga2O3 thin films with varying thicknesses is consistent. The critical loads for the elastic-plastic and plastic-brittle transitions are 9.4±1.8 mN and 50.7±2.7 mN respectively, while the scratch depths for the same are 91.8±7.8 nm and 216.4±10.1 nm, respectively. The critical adhesion and adhesive energy for the desquamation of the β-Ga2O3 film from the substrate are dependent on the thickness of the film. These results establish an experimental basis for understanding the mechanical behavior in the preparation and application of β-Ga2O3 thin films grown on sapphire substrates.