SURFACE-DIFFUSION OF GE ON SI(111) - EXPERIMENT AND SIMULATION

Surface diffusion of Ge on Si(111) at high temperatures has been exami ned experimentally by second-harmonic microscopy and computationally b y molecular-dynamics simulations with a Stillinger-Weber potential. Ex perimentally, the activation energy and preexponential factor for mass -transfer diffusion equalled 2.48 +/- 0.09 eV and 6 x 10(2+/-0.5) cm(2 )/s, respectively. Simulational results yielded essentially the same n umbers, confirming the utility of the Stillinger-Weber potential for d iffusional studies. A previously developed semiempirical correlation a lso did fairly well. The simulations also provided estimates for the c orresponding parameters for intrinsic diffusion and for the enthalpy a nd entropy of Ge adatom-vacancy pair formation on Si. The simulations further yielded evidence for minor contributions of atom exchange to i ntrinsic diffusion, as well as the complex high-temperature islanding phenomena on picosecond time scales.