Thin film absorbers for visible, near-infrared, and short-wavelength infrared spectra

In this study, the refractive indices were determined for Al2O3 films deposited with ALD, and amorphous Mo-Si-N films deposited with reactive sputtering. The measurements were made by spectroscopic reflectometry, ellipsometry, gonioreflectometry, and double-beam transfer standard spectrometry. Based on the results, two thin film absorbers were designed and manufactured: one for wavelengths of 350…1000 nm, the other for wavelengths of 1200…2000 nm. The manufactured absorbers showed high absorption over their whole working spectra varying from 93.4 % at the minimum to 99.9 % at the maximum. One of the absorbers was applied to a MEMS thermopile detector with successful process integration.