Scanning tunneling microscope characterization of nickel thin film nucleation and growth

Abstract

A study of the nucleation, growth and final microstructure of vacuum deposited nickel films has been performed using scanning tunneling microscopy (STM) as the primary research instrument. Typical nucleation conditions are reported for nickel films grown on partially shadowed highly-oriented pyrolytic graphite (HOPG), and techniques are developed for using the STM to catalog film islands instead of more conventional electron microscopes. Values for the activation energy of surface diffusion, critical nucleus size, changes in the saturation nucleation density with temperature, and spatial variations in the nucleation rate are included. Roughening and microstructure changes observed with STM are reported as functions of substrate temperature and deposition angle for nickel films grown on highly-oriented pyrolytic graphite and fused silica. Conventional film RMS roughness values are compared to microRMS values derived from STM data and STM images of film microstructure are compared with SEM and optical microscope photographs.