Preparation and characterization of sol-gel TiO2 antireflective coatings for silicon

Sol-gel polymeric TiO2 films have been obtained by dip coating. These films showed antireflective properties on silicon substrates as well as suitable adherent properties. The film thickness varied from 55 to 122 nm, and the refractive index presented values between 1.95 and 2.10. Both these parameters can be easily tailored by varying the withdrawal rate and the [TbuTi]/[Ethanol] ratio in the solution. The structural properties of the films showed that amorphous films are obtained by sintering at 450 degreesC, meanwhile, the nanocrystalline titania anatase phase is formed after heating the films at 850 degreesC for 5 s. By using these films, the hemispherical reflectance of polished silicon wafers is reduced in all the wavelength range and particularly, it is decreased from 37 to 1.5% at approximately 600 am. At the same time, the solar averaged reflectance of the uncoated silicon is reduced from 0.38 to 0.12 after the sol-gel TiO2 coating. (C) 2001 Elsevier Science B.V. All rights reserved.