We　investigated　annealing　effects　on　the　Ga2O3　thin　films　deposited　on　c-sapphire　by　plasma-enhanced　atomic　layer　deposition.　A　metastable　Ga2O3　films　was　deposited　on　c-sapphire　substrate　by　PEALD　with　high　plasma　power　at　250　degrees　C.　The　((2)　over　bar　01)　preferred　orientation　beta-Ga2O3　films　were　obtained　after　annealing　in　oxygen　atmosphere.　Structure　and　surface　analysis　revealed　that　the　annealed　films　had　more　fine-grained　surface　features.　The　film　annealed　for　2　h　exhibited　the　best　crystallinity.　The　bandgap　of　the　as-deposited　and　annealed　films　for　2　h　were　4.56　and　4.97　eV,　respectively.　The　process　of　high-temperature　annealing　contributed　gallium,　oxygen　atoms　to　obtain　enough　energy　to　migrate　to　the　suitable　location　and　increased　the　vigilance　of　crystallinity.　(C)　2018　Elsevier　B.V.　All　rights　reserved.