SN BULK-TO-SURFACE DIFFUSION IN A CU(111)(SN) SINGLE-CRYSTAL

The kinetics of the bulk-to-surface Sn diffusion in a dilute Cu(Sn)(11 1) single crystal had been investigated in the temperature range 678 t o 794 K using Auger electron spectroscopy and low energy electron diff raction. It is shown that a sputter time correction is essential to ob tain an accurate estimate of the diffusion coefficient D. After derivi ng the segregation equation for limited surface site accessibility, th e modified Darken equations are used, with sputter time corrections, t o determine the diffusion coefficient D and the segregation energy Del ta G from the kinetic data. The data and fits are characterised by a h igh degree of accuracy and the fit parameters have the following value s: D-0 = (7 +/- 6) x 10(-6) m(2)/s, E = 168 +/- 5 kJ/mol and Delta G = 76 +/- 3 kJ/mol.