Tantalum pentoxide (Ta2O5) thin films were grown by atomic layer deposition (ALD) using pentakis(dimethylamino)tantalum (PDMAT) and H2O at temperatures between 150 and 300 degrees C. A peak growth rate of 0.68 & Aring;/cycle was achieved at 200 degrees C. The as-deposited films from the optimal process are oxygen rich with an oxygen-to-tantalum (O/Ta) ratio of 3.3. Various thin film characterization methods were undertaken, and they showed that the as-deposited Ta2O5 films are amorphous and have a large optical bandgap of 4.1 eV. They possess a high breakdown strength of 3.9 MV cm(-1), a high electrical resistivity of 1 x 10(13) Omega cm, and a respectable dielectric constant of 14, indicating its suitability as high k dielectric materials in optical and electronic devices. Moreover, a phase transition to polycrystalline beta-Ta2O5 occurs after annealing at 700 degrees C, and it is stable up to 1000 degrees C.