PREPARATION OF SILICON DIOXIDE FILMS BY LOW-PRESSURE CHEMICAL VAPOR-DEPOSITION ON DENSE AND POROUS ALUMINA SUBSTRATES

Thin silicon dioxide films were grown on dense alpha-alumina wafers as well as porous alpha-alumina and gamma-alumina substrates by low pressure chemical vapor deposition (LPCVD), via oxidation of triisopropylsilane (C3H7)3SiH within a cold-wall LPCVD reactor. In the temperature range of 650 850-degrees-C deposition rates of 8 to 78 nm/min were attained. The SiO2 films were transparent, amorphous, uniform and they adhered very well to the alumina support. Most importantly, the films were dense, free of porosity and exhibited excellent stability for chemical applications. SEM images showed that SiO2 films grown on alumina wafers exhibit a featureless surface morphology, while the microstructure of films grown on porous alumina substrates consists of clusters of grains that are tightly packed together. Tailoring of ultrathin films on porous substrates by chemical vapor deposition offers attractive opportunities for the synthesis of high-temperature, selective ceramic membranes and the design of novel composite catalyst structures.