In situ TEM evaluation of the growth kinetics of Au particles on highly oriented pyrolithic graphite at elevated temperatures

Gold particles were vapor deposited onto thin substrates of highly oriented graphite at temperatures from 250 to 350 degrees C inside a transmission electron microscope. The growth kinetics of individual particles were recorded in real time. Mostly well faceted, Rat crystallites grew in epitaxial orientation with (111) faces on top. On substrate areas with low-defect density, particle numbers were in the range of some 10(9)/cm(2), independent of temperature. In highly defective areas, densities were up to 10(11)/cm(2). Condensation coefficients were measured in both areas by quantitative x-ray analysis as below 0.01, and around 0.1, respectively, during the early stages of growth, particle shapes mostly stayed constant during growth, while the projected areas were found to increase in proportion to deposition time. Capture rates of adatoms were determined quantitatively, and compared with calculations on the basis of a diffusion model, leading to a mean adatom diffusion length before desorption of 5.8 +/- 2.4 nm on defect free highly oriented pyrolytic graphite at 350 degrees C. This value corresponds to a difference of the atomic energies of adsorption and diffusion (E-a - E-d) = 0.39 +/- 0.04 eV.