The　intrinsic　and　Nb-doped　beta-Ga2O3　(beta-Ga2O3:Nb)　thin　films　have　been　deposited　on　the　Si　and　quartz　substrates　by　radio　frequency　magnetron　technique　in　argon　ambient.　The　effects　of　Nb　doping　on　the　structural　and　optical　properties　of　Ga2O3:Nb　thin　films　have　been　investigated.　After　Nb-doping,　the　crystal　lattice,　surface　morphology,　optical　transmittance　and　optical　energy　gap　of　the　beta-Ga2O3　films　are　greatly　changed.　The　crystal　lattice　of　the　beta-Ga2O3:Nb　films　is　augmented,　the　energy　gap　shrinks　and　the　crystalline　quality　is　improved.　XPS　spectra　shows　that　niobium　is　incorporated　into　the　oxide　matrix　and　present　in　the　(beta-Ga2O3　as　Nb(IV).　(C)　2017　Elsevier　Ltd.　All　rights　reserved.