Smoothening of (001) and (111) Cu films epitaxially grown on Si substrates

We report an i-situ study of the MBE growth of Cu films on hydrogen-terminated Si (001) and (7x7) reconstructed Si(111) substrates. Using correlated RHEED and STM data, we find a dramatic smoothing of epitaxial Cu(001) surfaces by annealing the as-grown films in the 120- 6 oC temperature range and somewhat less so for the Cu (111) films. Our measurements reveal a lower activation energy (0.40 + 0.04 eV) for inter-terrace mass transport in Cu(001) than for Cu(111) (1.10 + 0.03 eV) the former possibly influenced by the presence of hydrogen. Scaling analysis of the subsequent Cu growth on the annealed smooth surfaces yields a coarsening exponent of 1/4 for the (001) oriented films while this exponent is 1/3 for the (111) films, providing for the first time experimental data for the same system in these two orientations