An unusual growth mode has been observed during low temperature growth at Tϭ185 K in the system Pb/Si(111)-(7ϫ7) with the formation of uniform seven-step, steep-edged, flat-top islands up to coverages ϭ7.5 ML. The evidence is based on the spot profile analysis-low-energy electron diffraction diffracted intensity distribution as a function of k ʈ , k z the parallel and normal components of the momentum transfer which show sevenfold oscillations over the range in k z where single step oscillations are expected. The formation of these highly uniform, self-organized structures implies that unconventional kinetic mechanisms operate at these low temperatures.
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R10 604PRB 61
Self-organized islands of uniform heights can form at low temperatures on metal/semiconductor systems as a result of quantum size effects, i.e., the occupation of discrete electron energy levels in the film. We compare the growth mode on two different substrates [Si(111)- (7x7) vs Si(111)- Pb(sqrt[3]xsqrt[3] )] with spot profile analysis low-energy electron diffraction. For the same growth conditions (of coverage and temperature) 7-step islands are the most stable islands on the (7x7) phase, while 5-step (but larger islands) are the most stable islands on the (sqrt[3]xsqrt[3] ). A theoretical calculation suggests that the height selection on the two interfaces can be attributed to the amount of charge transfer at the interface.
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