PNNL

Abstract

Si:H/CaF2 and Si:H/HfF4 high reflectors with as many as 27 layers were deposited by a hybrid process that combined reactive magnetron sputtering and electron beam evaporation. The ultimate goal of this work was to deposit interference filters with low NIR and LWIR absorption for use in thermophotovoltaic systems. The high index Si:H layers were deposited by reactive magnetron sputtering in mixtures of Ar + H2. Electron beam evaporation was the preferred deposition method for the CaF2 layers. The multilayer hybrid coatings were deposited in the same chamber by sequentially rotating the substrate over the Si sputtering target and the CaF2 evaporation source. The deposition rate of the evaporated CaF2 was 18.3 Å/s, compared to 0.42 Å/s for sputtered CaF2. The deposition rate of the Si:H layers was 1Å /sec. The refractive index of the SiH at NIR wavelengths was 3.45, with extinction coefficient