A STUDY OF NIOBIA DEPOSITION ON ALPHA-AL2O3(0001) AND OXIDIZED AL

The deposition of niobia on oxidized Al films and on an alpha-Al2O3(0001) crystal was examined using Auger electron spectroscopy and high-resolution TEM. Vapor deposition of niobia resulted in amorphous, two-dimensional films which were stable upon heating up to at least 900 K in vacuum. The presence of niobia had no measurable effect on the acidity of the samples. Temperature-programmed desorption of 2-propanol and isopropylamine occurred from sharp desorption features at 185 and 140 K, respectively on all surfaces examined, indicating that no acid sites were present on any of the samples. An alternate approach to deposition of niobia using Nb(C2H5O)5 resulted in significant carbon contamination. The implications of these results to the formation of model, supported-oxide catalysts is discussed.