The initial stages of titanium growth on the 1×1 and (√84×√84)R11° terminations and chromium growth on the (√84×√84)R11° termination of α-quartz SiO2 (0001) have been studied using polarization-dependent SEXAFS. Three metal coverages have been examined: nominally 0.25, 0.5 and 1.0 ML. The Ti K-edge results evidence reduction of the selvedge through the formation of a titanium oxide; with metallic Ti clusters formed at higher coverages. Ti-O distances of 1.96-2.00±0.03 angstroms are observed along with Ti-Ti distances of 2.89-2.92±0.03 angstroms. The former range is close to the Ti-O bond distances in rutile, whereas the latter is within the experimental error of that of bulk titanium. The Cr K-edge results are consistent with the formation of 15 atom clusters having an average nearest-neighbour Cr-Cr distance of 2.36±0.03 angstroms. This represents a contraction of about 6% from the bulk bcc lattice spacing. Such a contraction is consistent with the prediction of recent calculations.
- Chromium growth
- Titanium growth