The transition to step flow growth on the clean and surfactant covered Si(111) surface studied by in-situ LEEM

The transitions to step flow growth on the clean Si(111) (7x7), Si(111)-In (root3 x root3)R30degrees 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 750degreesK. 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 (root3 x root3)R30degrees surfaces that are morphologically suitable for step flow growth are also described.