Optical properties of ion-beam sputtered TiO/sub 2/ films

Ion-beam sputtered TiO/sub 2/ films were simultaneously deposited onto Corning 7059 and silicon substrates for ellipsometric and spectrophotometric investigation of optical parameters. Film thicknesses ranged from 5 to 500 nm, and spectrophotometer wavelengths from 400 to 2500 nm. Results from the two techniques agree well at the 632.8 nm wavelength used for ellipsometry. At thicknesses above 100 nm and wavelengths above 1 μm, the TiO/sub 2/ refractive index was insensitive to changes in thickness or wavelength. It increased, as expected, at shorter visible wavelengths, and it decreased markedly for films below 100 nm in thickness. The index varied with the oxygen to argon ratio of the ion beam, showing a maximum value of 2.52 for 632.8 nm wavelength light. The extinction coefficient was too small for spectrophotometric measurement in the infrared; previous calorimetric measurements for half wave films at 1.06 μm showed absorption below 100 p/m. The extinction coefficient, however, increased in the visible, typically reaching values corresponding to a few tenths percent absorption at 0.4 μm