K. Okumura et al., GROWTH OF PT-RH ALLOY CRYSTALLITES ON ALPHA-AL2O3 STUDIED BY ATOMIC-FORCE MICROSCOPY AND RUTHERFORD BACKSCATTERING SPECTROSCOPY, JOURNAL OF PHYSICAL CHEMISTRY B, 102(13), 1998, pp. 2350-2355
The growth of Pt-Rh alloy crystallites vacuum-deposited on alpha-Al2O3
substrates by thermal treatment was investigated by atomic force micr
oscopy (AFM) as a function of Rh concentrations. As-deposited Pt thin
film without any Ph concentration changed into Pt crystallites dispers
ed on the substrate by annealing at 800 degrees C in oxidative and red
uctive atmospheres. The oxidative atmosphere remarkably enhanced the g
rowth of Pt crystallites, while it is not the case in the growth of pu
re Rh crystallites. However, when Rh was added to Pt, the crystallites
remained very small and highly dispersed on the substrates even after
the annealing at 800 degrees C in an oxidative atmosphere. We also in
vestigated the surface concentration of Pt and Rh by Rutherford backsc
attering spectroscopy (RBS) and discussed the effect of wettability of
Ph oxide as a key role in inhibiting the growth of Pt-Rh crystallites
.