Characterization of GeO2Sub-monolayers on SiO2Prepared by Chemical Vapor Deposition of Ge(OMe)4by EXAFS, FT-IR, and XRD

Abstract

GeO2 sub-monolayers on SiO2 surfaces were prepared by the chemical vapor deposition (CVD) reaction of Ge(OMe)4 with OH groups on SiO2 at 393 K, followed by calcination at 693 K. The characterization of the obtained GeO2/SiO2 was conducted by FT-IR, XRD, and EXAFS. Isolated OH groups on SiO2 preferentially reacted with Ge(OMe)4. The Si−OH peak was significantly depleted by the CVD reaction of Ge(OMe)4 and partially reappeared to half of the original Si−OH peak after calcination. The linear increase of the Ge−OH peak and the linear decrease of the Si−OH peak with increased Ge loading suggest a monolayer growth of GeO2. The coverage of GeO2 at saturation for the sample prepared by the one-cycle CVD process was estimated to be 1/5 monolayer of the SiO2 surface, which corresponds to 7.4 wt % Ge loading. There existed only isolated Ge−OH groups on the GeO2 layers, which is contrasted to the case of bulk GeO2, which shows both isolated and hydrogen-bonded OH groups. The surface of the GeO2 layers on SiO2 has no ...