Epitaxial growth of ultrathin Pt films on basal-plane sapphire: The emergence of a continuous atomically flat film

Epitaxial Pt films of various thicknesses were grown on basal-plane sapphire using ion beam sputtering. Scanning tunneling microscope images are used to characterize the film morphologies and their dependence on deposition temperature, TD. Epitaxial characteristics are determined, in a qualitative sense, by low-energy electron diffraction (LEED). The film morphologies are very sensitive to TD - exceeding the narrow ideal temperature range of 580-590°C means the difference between a relatively flat Pt film and a surface with tall Pt mounds separated by bare sapphire patches. Within this temperature range, Pt islands are observed at 10 Å, these islands begin to coalesce at 15 Å, and continuous films are observed at 30 Å and 50 Å. The continuous films are nearly ideal atomically flat surfaces, but both show several exposed Pt layers and the 30 Å film has many pinholes. Also, images of 5 Å Pt films deposited at room temperature are used to characterize the substrate morphology. © 1998 Elsevier Science B.V.