Influnence of the substrate and thickness of HMVF layers on performance of NbSiN/NbSiNO/Si₃N₄ tandem

NbSiN/NbSiNO/Si₃N₄ and Mo/NbSiN/NbSiNO/Si₃N₄ multilayer Films were deposited on single-sided polishing stainless steel and Cu substrates by a reactive magnetron sputtering system. Four Nb chips (99.95%, Φ60 mm×3 mm) were put on the polysilicon target. The thickness and optical performance were investigated by DEKTAK IIA X-step, UVPC3100 spectrophoto-meter and EXCALIBUR FTS 3000 Fourier Transform Infrared Spectrophotometer (FTIR). It was found that a high solar absorptance (0.90) and low emittance (0.12) on Cu substrate has been obtained. Infrared reflectance is relatively high when Mo layer thickness is 230 nm at>2.5 μm of wavelength. The surfaces exhibits high absorptance α=0.95 and emittance ε=0.33 when high metal fraction volume (HMVF) layer thickness is about 80 nm. The coating remains stable in vacuum up to 600°C for 20 hours.