Sputtered Si:H alloys for edge filters: application to thermophotovoltaics

Si:H alloys are being investigated for the high-index material in an interference filter to provide spectral control in an application of thermophotovoltaic energy conversion. In particular, a multilayer edge filter is being developed to provide high transmission of photons with wavelengths between 1.0 and 2.4 microm and high reflectance for wavelengths outside this range. Thin films of Si:H were deposited by means of rf reactive sputtering. Deposition parameters were varied to optimize the H content in Si:H coatings such that the refractive index was greater than 3. Optical absorption near 1 microm and Si:H infrared absorptions near 5 and 12 microm were minimized.