Langmuir 1993,9, 3497-3506
3497
Dispersion and Distribution of Titanium Species Bound to Silica from Tic14 Suvi Haukka,**+J Eeva-Liisa Lakomaa,+JOlli Jylha,s Juha Vilhunen,) and Seppo Hornytzkyj) Microchemistry Ltd., P.O. Box 45,02151 Espoo, Finland, Department of Chemistry, Analytical Chemistry Division, University of Helsinki, P.O. Box 6, 00014 Helsinki, Finland, and Neste Oy, Scientific Services, Analytical Research, P.O. Box 310,06101 Porvoo, Finland Received July 8,1993.I n Final Form: September 17,199P The paper examinesthe effects of the porous high surface area silica support and the reaction temperature
(175-550 "C) on the dispersion and distribution of the titanium species formed during a single saturating
reaction cycle of Tic&,used in preparing Titsilica samples by atomic layer epitaxy (ALE). Samples were analyzed by chemical etching, X-ray powder diffraction (XRD), scanning and transmission electron microscopy (SEM,TEM),and X-ray photoelectron spectroscopy( X P S ) . The reactions were highly surfacecontrolled, i.e. controlled by the OH groups of silica, which determined the numbers of titanium atoms bound. Only amorphous titanium species was formed at lower reaction temperatures (
