Single layers of TiO2 and TiN films, as well as triple layer structures of TiO2/TiN/TiO2, have been sputtered on substrates at temperatures ranging from room temperature to 450 °C. A new combination of materials was used to make the substrate heater. X-ray diffraction (XRD) was used to study the infiuence of substrate temperature upon the grain size. The optical constants n and k for TiO2 were evaluated. The oxide films grown at a higher deposition rate and on 300 °C substrates had a refractive index of 2.48 at 550 nm, compared to 2.29 for the film grown at a lower rate and at room temperature. A single layer of TiN exhibits improved optical selectivity with increased substrate temperature up to 300 °C. Further increase of the substrate temperature only caused a small effect on the heat mirror properties of the film. The triple layer is improved with increased substrate temperature. However, at temperatures of 300 °C and higher, a reduction of the heat mirror performance occurs and it is demonstrated by optical multilayer calculations that this is probably due to oxide growth on the outer TiN-TiO2 interface.
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Georgson et al. (1991) studied this question.