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

In this work, the phase transition process of fi-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, fi-Ga2O3 did not undergo phase transition even when the temperature was up to 1000 degrees C. When under electron irradiation condition, the unconventional phase transition from fi-Ga2O3 to delta-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 fi-Ga2O3 parent phase as following: [010]fi//[011]delta, (200)fi//(211)delta, and (402)fi//(411)delta. The results reveal that electron irradiation can trigger the phase transition process from fi-Ga2O3 to delta-Ga2O3, and the high temperature obviously accelerates the rate of phase transition process.