Atomically resolved interface structures of vacuum-deposited Pt on SnO₂(110), (101), and (111)

We investigated atomically resolved interface microstructures of vacuum-deposited Pt on SnO₂(hkl) (hkl = 110, 101, 111; Pt/SnO₂(hkl)) substrate surfaces. The Pt/SnO₂(hkl) samples were prepared by electron-beam deposition of a 1.6-nm-thick Pt layer on SnO₂(hkl) at room temperature under ultrahigh vacuum (∼10⁻⁸ Pa) followed by thermal annealing. Cross-sectional structural analysis was conducted by scanning transmission electron microscopy combined with x-ray energy dispersive spectroscopy and x-ray photoelectron spectroscopy. The Pt/SnO₂(101) and Pt/SnO₂(111) samples clearly showed Pt(111) epitaxial growth on the SnO₂(101) and (111) substrate surfaces, whereas an islandlike Pt growth was observed on SnO₂(110). Increasing the annealing temperature of the samples from 473 to 673 K resulted in alloying of the deposited Pt with Sn atoms from the substrate in the case of Pt/SnO₂(110). In comparison, for Pt/SnO₂(101) and Pt/SnO₂(111), the interfaces were atomically steep, and no Pt–Sn alloys were generated even on 673 K annealing. The results clearly showed that the morphologies of the deposited Pt and the thermal diffusion behaviors of the Pt and substrate Sn atoms, i.e., the Pt/SnO₂ interface microstructure, are determined by the lattice matching of the deposited Pt and SnO₂ substrate interface.