Search

The transitions to step flow growth on the clean Si(111) (7x7), Si(111)-In (&radic3; x &radic3; )R30° and Si(111)-Sb d(7x7) surfaces have been investigated using low energy electron microscopy (LEEM). The critical terrace width for step flow on the clean surface displays an Arrhenius behaviour, although with markedly different prefactor and activation energy above and below 750°K. The abrupt change in Arrhenius parameters was revealed by LEEM to correlate with the crossover from homogeneous to heterogeneous island nucleation behavior. The dependence of the critical terrace width upon step orientation is attributed to anisotropic step attachment kinetics. Sb and In surfactants were found to suppress and enhance step flow, respectively, in accordance with expectations. The preparations of Si(111)-Sb d(7x7) and Si(111)-In (&radic3; x &radic4;)R30° surfaces that are morphologically suitable for step flow growth are also described. [ABSTRACT FROM AUTHOR]

Mass transport in the Pb wetting layer on the Si(111) surface is investigated by observing nonequilibrium coverage profile evolution with low energy electron microscopy and microlow energy electron diffraction. Equilibration of an initial coverage step profile occurs by the exchange of mass between oppositely directed steep coverage gradients that each move with unperturbed shape. The bifurcation of the initial profile, the shape of the profile between the two moving edges, and the time dependence of equilibration are all at odds with expectations for classical diffusion behavior. These observations signal a very unusual coverage dependence of diffusion or may even reveal an exceptional collective superdiffusive mechanism. [ABSTRACT FROM AUTHOR]