Electron-irradiation induced unconventional phase transition of β-Ga2O3 epitaxial single-crystal thin film observed by in-situ TEM

In this work, the phase transition process of β-Ga2O3 thin films under heating and (or) electron irradiation condition was investigated by in-situ transmission electron microscopy. It is found that only under the high temperature, β-Ga2O3 did not undergo phase transition even when the temperature was up to 1000 °C. When under electron irradiation condition, the unconventional phase transition from β-Ga2O3 to δ-Ga2O3 occurred with a slow rate. When electron irradiation was coupled with a thermal field, the initial temperature of phase transition decreased, and the speed of phase transition also greatly accelerated. The new phase maintains crystallography relationship with the β-Ga2O3 parent phase as following: [010]β//[011¯]δ, (200)β//(2¯11)δ, and (402¯)β//(411)δ. The results reveal that electron irradiation can trigger the phase transition process from β-Ga2O3 to δ-Ga2O3, and the high temperature obviously accelerates the rate of phase transition process.