摘要
We report on a detailed low-energy electron diffraction (LEED) and low-temperature scanning tunneling microscopy (STM) study of the intermetallic surface compound CePt5 on Pt(111). Depending on the thickness we observe various diffraction patterns and superstructures. In the low-thickness regime a slightly compressed (2×2) superstructure is aligned along the 11¯0 direction of the Pt(111) substrate. STM reveals another, much larger superstructure with a periodicity of (9.02±0.45) nm presumably responsible for the strongly broadened LEED spots. At about 3 unit cells (u.c.) the surface is dominated by a (33×33)R30' pattern as revealed by LEED satellites and Fourier-transformed high-resolution STM images. It is interpreted as a moiré pattern between the film and the substrate. We precisely determine the superstructure of the intermetallic film to (1093×1093)R30' with respect to the Pt(111) substrate. Above 3 u.c. the satellites progressively disappear. A model is developed that consistently describes this thickness-dependent transition. For CePt5 films with a thickness between 6 and 11 u.c. the lattice of the compressed (2×2) superstructure rotates back into the substrate's 11 directions.