IR characterization of graphite black-coating for cryogenic detectors

We are developing an infrared thermal sensor to meet the growing needs of such detectors, operating at room and cryogenic temperature. For these facilities, two types of optical absorbing coatings were investigated. First was graphite-black coating and second was matt black paint, both are deposed on substrates simply by spray. IR spectroscopy measurements made on graphite layer revealed that reflectance at normal incidence varies by less than 10% at 10 μm and at 20 μm. Hence, thermal sensors using this coating had high and flat spectral sensitivity from 2.5 μm to 20 μm. These results are compared to measurements made on matt black paint and gold-black coatings documented in bibliography. Electrical characterization at room and cryogenic temperature indicated that graphite-black had a temperature coefficient of 5.510−3 K−1 at 300 K and −5.110−3 K−1 at 80 K, while matt black paints was electrically insulator.