Preparation of aluminosilicate crystalline coatings from sol-gel derived alumina films deposited on silicon/silica substrates
Abstract
The dedicated formation of crystalline coatings of the trimorphous aluminosilicates with the composition of Al2SiO5 starting from a low-cost sol-gel deposition of alumina thin films is reported. The influence of substrate type and film thickness on the crystallisation behaviour and film morphology is studied by means of wide-angle X-ray scattering (WAXS) and X-ray reflectometry (XR). When annealed at a temperature of 1150 °C under high-vacuum conditions, formation of the aimed phases was achieved only for films deposited on naturally oxidised Si-substrates covered with a thin silica layer (thickness is about 3 nm). In the case of films deposited on amorphous quartz glass and thermally oxidised Si-substrates covered with a thick silica layer (thickness is about 500 nm) no crystallisation occurred at this temperature. After annealing at the higher temperature of 1300 °C under high-vacuum conditions, in the films deposited on both kinds of Si-substrates mullite (Al4SiO8) crystallises together with cristobalite (SiO2) whereas the film deposited on the quartz glass substrate remains amorphous from viewpoint of WAXS. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
