Preparation of SiO 2 overlayers on oxide substrates by chemical vapor deposition of Si(OC 2H 5) 4

Abstract

The deposition of SiO 2 onto ZrO 2, TiO 2, MgO, SiO 2 and Al 2O 3 by chemical vapor deposition (CVD) of Si(OC 2H 5) 4 was studied by temperature programmed desorption (TPD) and Auger electron spectroscopy (AES). TPD showed that Si(OC 2H 5) 4, adsorbed at 300 K, decomposed on ZrO 2, TiO 2, MgO and Al 2O 3 to give ethene and H 2O during the TPD. SiO 2 did not adsorb Si(OC 2H 5) 4 at 300 K. The decomposition of Si(OC 2H 5) 4 on ZrO 2 decreased as the amount of SiO 2 grew. The Zr AES signals attenuated strongly while that of Si increased. We conclude that a SiO 2 thin film about 10 Å thick forms on ZrO 2. This thin film was stable in vacuum up to 723 K but, at 823 K, either rearranged into small clusters or formed a solid solution with the surface of ZrO 2. The decomposition activity of TiO 2 for Si(OC 2H 5) 4 did not decrease strongly as SiO 2 deposition proceeded. This is accounted for if SiO 2 clusters are produced leaving TiO 2 sites exposed. Over both ZrO 2 and TiO 2 adsorption of CO 2 was suppressed by the deposition of SiO 2. There is no significant carbon buildup during deposition on ZrO 2 but on all the other oxides its accumulation is important.