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 sa pphire using ion beam sputtering, Scanning tunneling microscope images are used to characterize the film morphologies and their dependence o n deposition temperature, T-D. Epitaxial characteristics are determine d, in a qualitative sense, b) low-energy electron diffraction (LEED). The film morphologies are very sensitive to T-D - exceeding the narrow ideal temperature range of 580-590 degrees C means the difference bet ween a relatively nat Pt film and a surface with tall Pt mounds separa ted by bare sapphire patches, Within this temperature range, Pt island s are observed at 10 Angstrom, these islands begin to coalesce at 15 A ngstrom, and continuous films are observed at 30 Angstrom and 50 Angst rom. The continuous films are nearly ideal atomically flat surfaces, b ut both show several exposed Pt layers and the 30 Angstrom film has ma ny pinholes. Also, images of 5 Angstrom Pt films deposited at room tem perature are used to characterize the substrate morphology. (C) 1998 E lsevier Science B.V.