FURTHER OPTION FOR SOLAR CONCENTRATORS - ALUMINUM FIRST SURFACE MIRRORS

The research and development of aluminum first surface solar miners is presented. Two protection films for the aluminum layer are discussed: Si2O3 and SiO2. Two electron guns (e-gun) are used to manufacture aluminum first surface solar mirrors. One, for aluminum evaporation, eliminates or minimizes pinholes observed when aluminum is evaporated with tungsten filaments. The other e-gun allows the evaporation of SiO and SiO2 without the mirror contamination previously seen due to the air when the chamber was opened. Better adherence between the aluminum film and the Si2O3 or SiO2 is obtained due the use of two electron guns that does not permit the chamber to open. Si2O3 is a material obtained by oxidation of SiO by admitting some oxygen into the evaporation chamber (10(-4) Torr). The optimum thickness of the aluminum layer was 1000 Angstrom or higher, about 2500 Angstrom for the Si2O3, and 3200 Angstrom for the SiO2. The specular reflectance of these mirrors is about 0.89. These mirrors were tested in the environmental chamber for accelerated weathering without any important degradation, making them another option for solar concentrators in solar energy applications.