Surface diffusion of Ge on Si(111): Experiment and simulation

Abstract

Surface diffusion of Ge on Si(111) at high temperatures has been examined experimentally by second-harmonic microscopy and computationally by molecular-dynamics simulations with a Stillinger-Weber potential. Experimentally, the activation energy and preexponential factor for mass-transfer diffusion equalled 2.48\ifmmode\pm\else\textpm\fi{}0.09 eV and 6\ifmmode\times\else\texttimes\fi{}${10}^{2\ifmmode\pm\else\textpm\fi{}0.5}$ ${\mathrm{cm}}^{2}$/s, respectively. Simulational results yielded essentially the same numbers, confirming the utility of the Stillinger-Weber potential for diffusional studies. A previously developed semiempirical correlation also did fairly well. The simulations also provided estimates for the corresponding parameters for intrinsic diffusion and for the enthalpy and entropy of Ge adatom-vacancy pair formation on Si. The simulations further yielded evidence for minor contributions of atom exchange to intrinsic diffusion, as well as the complex high-temperature islanding phenomena on picosecond time scales.