SCANNING-TUNNELING-MICROSCOPY OF THE NUCLEATION AND GROWTH OF SPUTTER-DEPOSITED CR ON GRAPHITE

In this paper, we present a study of the nucleation and growth stages of sputter-deposited Cr thin films on highly oriented pyrolytic graphi te (HOPG) substrates using scanning tunnelling microscopy (STM) in air . Freshly cleaved HOPG surfaces and those modified by Ar+ ion bombardm ent were used as substrates. For short deposition times, two-dimension al (2D) chromium clusters on the graphite substrate were observed. Wit h an increase in deposition time, the formation of three-dimensional ( 3D) clusters occurred. The number of surface defect sites influences t he number and size of clusters formed on the graphite substrate. The f ormation and surface diffusion of 2D and 3D clusters play a dominant r ole in the subsequent stages of the nucleation of chromium thin films. The results of our investigation show clearly that the most important contribution to the elementary mechanism of growth is the phase trans ition from 2D to 3D clusters and their condensation into larger 3D clu sters.