Auger electron spectroscopy of the kinetics of evaporation of palladium beaded films from sapphire substrate

Kinetics of morphological changes of beaded Pd him on the (10 (1) over bar (2) over bar) surface of sapphire were investigated by Auger electron spectroscopy in the temperature range of 1053-1083 K. It was found that the decrease of the effective thickness during heat treatments under 10(-8) mbar was caused by evaporation from the surface of the substrate. Using the model developed by Kaganovskii and Beke we have established that the process is controlled by surface diffusion. It was shown that the evaporation rate of palladium adatoms from an alumina surface is given by I-o = 1.45 x 10(36) exp{-(393 +/- 46 kJ/mol)/RT}m(-2)s(-1), and, on the basis of an estimation of the surface diffusion length, the effective surface diffusion coefficient D-s' was evaluated: D-s' = 1.2 x 10(4) exp{- (393 +/- 46 kJ/mol)/RT}m(2)s(-1).