Ion beam deposition of tantalum pentoxide thin film at room temperature.

Tantalum pentoxide (Ta₂O₅) thin films have been deposited by reactive ion beam sputtering at room temperature. The films have been characterized by scanning electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), variable angle ellipsometry, and UV-VIS spectroscopy. The main parameter varied was the oxygen partial pressure. Stoichiometry is reached for p_O>=3×10^-2 Pa; within the limit of XPS (∼1%) the films are free of contaminations. They are extremely smooth with a surface roughness of 0.14 nm only. From FTIR, it can be concluded that they are amorphous. For stoichiometric Ta₂O₅ films, the refractive index at 532 nm is in the range from 2.05 to 2.2, while the extinction coefficient is below the detection limit of our ellipsometer. UV-VIS spectra show stoichiometric films to possess a high transmission in a wide wavelength range with an absorption edge below 300 nm. [ABSTRACT FROM AUTHOR]