Gold-alumina cermet photothermal films

Cermet films of gold and aluminum oxide were sputter deposited onto silicon substrates. These films consisted of nanometer-sized gold grains embedded in a matrix of aluminum oxide and were designed to absorb visible radiation and minimally emit infrared radiation. Ex situ and in situ spectroscopic ellipsometry were used to characterize film optical constants from deep ultraviolet to middle infrared. The optical constants, for cermet films with gold volume fractions ranging from 0 to 1, were used in predictive optical models. Thermal performance was optimized using a new algorithm based on energy balances. This algorithm weights the parameter fit in predictive optical models to an ideal reflectance spectrum. This weighting factor emphasizes fitting in more significant spectral ranges and de-emphasizes fitting in less significant wavelength ranges. Absorptivity, emissivity, and their ratio were calculated for optimized film structures.