Preparation Of Fe-doped AlN Films And Design Of Colored Solar Selective Absorbing Films

More and more attention has been paid to the exploitation and application of soalr energy because of use up of unrenewable energy such as petroleum, coal, and natural gas. As an important usage of solar energy, colored solar selective absorbing films have the advantages of high solar-thermal conversion efficiency, low thermal emittance, and compatibleness with the color and architecture of the buildings. Therefore, this dissertation will focus on the preparation and design of solar selective absorbing films. Effect of substrate temperature on optical properties of bismuth oxide thin films, and the optical and structural properties of Fe-doped AlN films prepared by reactive DC magnetron sputtering had been investigated. The colored solar selective absorbing films with three-layer structure had been designed and analyzed. The main contents are arragned as follows.Firstly, bismuth oxide films were deposited on glass substrates by direct current magnetron sputtering and the substrate temperature was changed from room temperature to300℃. The effect of substrate temperature on the optical properties of the films was investigated. Experimental results showed that the intensity of Bi2O3(120) diffraction peak became stronger and the surface particle size become smaller as the increasing of substrate temperature, Bi2O2.75(006) diffraction peak appeared when the substrate temperatures were250℃and300℃. As the increasing of temperature, the refractive index decreases, and extinction coefficient ranged between102and10-1. The optical band gap varied between3.51eV and3.04eV.Secondly, Fe-doped AlN films were deposited on n-type Si (100) and quartz substrates by a reactive direct current magnetron sputtering system in an atmosphere of Ar and N2at room temperature. The target was a mixture of Al and Fe with a weight ratio10:1. The results show that the films are amorphous when FN2is less than3cm3/min. AlN (100) diffraction peak can be seen in all the samples as FN2is larger than6cm3/min. Fe3N (202) and AlN (103) peaks are found in the samples at FN2of20and30cm3/min. AlN (110) peak appears at40cm3/min sample. Optical transmittance of the film on quartz substrates increases with increasing FN2. The maximum transmittance is higher and the optical energy gap increase Finally, using the effective medium theories, the optical constants of Fe doped AlN films with different Fe volume fraction were calculated. Using glass with200-nm Cu film as substrate, colored solar energy selective absorbing film with three-layer structure had been designed. The volume fraction of Fe decreased step by step in the three layers, the first layer, interlayer, and anti-reflection layer. The effect of the thickness of each layer and Fe volume fraction in the interlayer on the reflectivity of selective absorption film had been analyzed. The color includes orange yellow, green, pink partial purple, purple, and pink. The change of the performance for the green film with angle of light incidence had been analyzed. When the incident angle increases from0°to50°, the color changes from green to blue, and both the absorptance and emittance decrease.