Ion implantation-induced nanoclusters were synthesized in reactive sputtered Ta2O5 films by Ge+ implantation and subsequent annealing. The effects of ion fluence and post-implantation thermal treatment on the kinetics of the nanoclustering were investigated. Ge+ ions with energy of 40 keV and fluences of 5×1015, 1×1016 and 5×1016 cm− 2 were implanted in the Ta2O5 layers at room temperature. The samples were thermally treated by rapid thermal annealing in vacuum at 700 °C and 1000 °C for 30, 60 and 180 s. Structural studies of all samples were done by Crosssectional Transmission Electron Microscopy in diffraction and phase contrast mode. Under optimized conditions (high implantation fluence, subsequent annealing) nanoclusters are formed around the projected ion range of the implanted Ge+ ions. The structure of the implanted Ta2O5 matrix changes from amorphous to orthorhombic when the annealing was performed at 1000 °C. Although the Ta2O5 matrix crystallizes, no evidence is obtained for crystallization of the embedded nanoclusters even after annealing at 1000 °C.