Some Aspects Regarding I. R. Absorbing Materials Based On Thin Alumina Films for Solar-Thermal Energy Conversion, Using X-Ray Diffraction Technique
Solar energy is the most “available”, ecological and clean energy. This energy can be used in active or passive mode. The active mode implies the transformation of solar energy into a useful energy. The solar energy can be transformed into thermal energy, using solar collectors. In these collectors, the active and the most important element is the absorber, material which performs the absorption of solar radiation and, in at the same time, limits its reflection. The paper presents some aspects regarding the IR absorbing material – a type of cermets, used as absorber in the solar collectors, by X Ray Diffraction Technique (XRD) characterization. Keywords—Alumina films, solar energy, X-ray diffraction.
Al2O3 thin films by plasma-enhanced chemical vapour deposition using trimethyl-amine alane (TMAA) as the Al precursor

2O3 thin films by plasma-enhanced chemical vapour deposition (PECVD) using trimethyl-amine alane (TMAA) as the Al precursor. The thin films were deposited on both Si and quartz silica (SiO2) substrates. Deposition rates were typically 60 Å min-1 keeping the TMAA temperature constant at 45 °C. The deposited Al2O3 thin films were stoichiometric alumina with low carbon contamination (0.7–1.3 At%). The refractive index ranged from 1.54 to 1.62 depending on the deposition conditions. The deposition rate was studied as a function of both the RF power and the substrate temperature. The structure and the surface of the deposited Al2O3 thin films were studied using X-ray diffraction, atomic force microscopy (AFM) and scanning electron microscopy (SEM).

Chemical vapour deposition of κ-Al2O3
Abstract The influence of experimental variables in combination with catalysis on the growth and microstructure of chemically vapour deposited κ-Al 2 O 3 was investigated. The Al 2 O 3 coatings were deposited in the temperature range of 800–1000°C and at pressures of 50–400 mbar. Hydrogen sulfide (H 2 S) was used as a doping/catalysing agent. General deposition characteristics of κ-Al 2 O 3 as a function of temperature, pressure and H 2 S concentration are reported. In addition to scanning electron microscopy and X-ray diffraction, the microstructure and chemistry of the κ-Al 2 O 3 layers were analysed using transmission electron microscopy. The growth rate of κ-Al 2 O 3 could be strongly enhanced by applying H 2 S doping and reasonable deposition rates for κ-Al 2 O 3 could be obtained at 800°C. Relatively very high growth rates could be obtained by increasing the total pressure simultaneously with H 2 S doping. Higher deposition pressure, however, increased the contribution of the homogenous gas phase reaction resulting in unacceptable thickness variations. In general, κ-Al 2 O 3 deposited at different process conditions did not exhibit any pronounced microstructural or morphological differences, except at the deposition temperature of 800°C together with at higher doping levels (H 2 S>0.8%). Under these experimental conditions γ-Al 2 O 3 was obtained. Enrichment of sulfur could be confirmed to occur in γ-Al 2 O 3 while no sulfur was found in κ-Al 2 O 3 . Production-scale aspects concerning deposition of κ-Al 2 O 3 and α-Al 2 O 3 will be dealt with.