<title>Chemical composition of TiNxOy solar selective absorbers</title>

Abstract

TiNXOY films were prepared by activated reactive evaporation (ARE) [1J on copper to produce a tandem solar absorber exhibiting a low emissivity c(250 °C) 0.05. The optical selectivity of the absorber is determined by the preparation conditions. Coatings deposited with different nitrogen to oxygen (pN2 /po2) gas pressure ratios, show that maximum c is obtained when the ratio PN2 /po2 is held 8. The chemical composition of these TiNXOY films was determined by x-ray photoelectron spectroscopy (XPS) and related to solar selective properties. The investigated samples consist of about 38 -42 atomic % titanium, 35 -37 at% oxygen and 21 -23 at% nitrogen (bulk values), depending on preparation conditions. A depth profile indicates an oxygen enrichment at the surface, partially due to the exposure of the samples to atmosphere.After sputtering the photoelectron spectra show a marked peak at the TiO and TiN positions and a weaker one at the Ti02 position. Therefore, with regard to the known composition, the film is mainly a TiO(-N) compound with a small admixture of Ti02 . The surface layer is almost entirely consisting of Ti02. Additionally there might also be a small amount of TiC. (3 at% carbon impurity was detected)

<title>Thermal and chemical metallic-dielectric transitions of TiNxOy-Cu absorber tandems</title>

“…The experiments did not lead to film degradation which is prevented by the Si02 barrier film. This has been confirmed by XPS measurements under UHV conditions [14], where only the Ti02 signal decreases little in time but TiN and TiO signals remained constant. Although (t9 > 600) of tempered samples is greater than before treatment its contribution to the hemispherical emittance remains small due to the cos(t9) factor.…”

“…Normal emittance of copper is increased by 0.05 when covered with 100 nm TiNXOY (see fig.8, 'copper' and 'as received'). Evidence for Ti2N has been obtained by a peak at 78.4 0 However this phase was not observed in XPS measurements [14]. The measured maximum at 82 °i s considerably higher than calculated which is not yet understood.…”

“…The deposition process ARE (Activated Reactive Evaporation) and detailed properties of coatings prepared under different conditions are reported elsewhere [3,14]. Titanium is evaporated with an electron gun in a reactive gas mixture of nitrogen and oxygen.…”

<title>Optimization of SiO2-TiNxOy-Cu interference absorbers: numerical and experimental results</title>

“…Using an antireflecting coating instead of roughness has the advantage of achieving a steeper rise of reflectance at This explains the lower emittancies observed in the presented films compared to the emittancies of rough ones [1 1] . Eitle et al [31] observed on uncovered TiNZOY a change from more dielectric to metallic behavior (i. e. rise in k) when examing the films at 400 °C in vacuum. In contrast we have no possibility to produce predicted rough surfaces.…”

Deposition of Ti-Zr-O-N films by reactive magnetron sputtering of Zr target with Ti ribbons

“…In addition, it has been previously observed that the composition of Zr-O-N films from literature was localized in a very specific region of the Zr-O-N ternary diagram [17] , which could explain the observed color restrictions. Titanium oxynitride coatings are also used in a broad range of applications such as solar collector devices [18,19], diffusion barriers [20,21], isolation films in metal-isolatormetal structures [21], wear resistance coatings [22], among others. In terms of decorative applications TiN films are known for their golden appearance [23,24], and ranges of colors from metallic grey to gold and red brownish were also reported in TiN films [25].…”