|
The goal of the present study was the elucidation of the level, down to which it is possible to reduce a reflectivity of aluminium in visible, near infrared, and vacuum ultraviolet wavelengths ranges by introduction of nitrogen atoms into the skin layer of aluminium. The used method consists in coprecipitating the aluminium and nitrogen ions, such that the nitrogen atoms introduced into the lattice of aluminium cause infringements of periodicity of the aluminium crystal lattice field owing to local deformations when forming strong and spatially-oriented covalence bonds with surrounding aluminium atoms. In such deformed Al-N system, namely, on borders of areas with broken periodicity of the Al lattice field, there will take place a scattering of free electrons. An increase in electron scattering intensity within the skin layer results in reduction of probability of release of secondary photons by free electrons excited by light wave in the skin layer. The latter will cause reduction of reflectivity of the surface of deformed aluminium lattice. Reflectivity measurements of samples of Al-N were carried out at ten wavelengths within a range from 400 up to 927 nm, and also at 121.6 nm. It turned out, evaporation of aluminium in argon plasma containing the nitrogen is really capable to lower reflectivity of such coating to values acceptable for practical applications, just down to a level of 4% in a visible range, 5% in near infrared, and 2% at 121.6 nm. So low levels of reflectivity (especially, at 121.6nm - the most intensive line of the short-wave part of ultraviolet solar spectrum) allow to apply this coating for reduction of solar stray light in instruments and to decrease the detectors noise of space equipment operating under conditions of open space and intensive solar ultraviolet illumination.
|
