Uniform, self-organized, seven-step height Pb/Si(111)-(7×7) islands at low temperatures

An unusual growth mode has been observed during low temperature growth at T=185 K in the system Pb/Si(111)-(7×7) with the formation of uniform seven-step, steep-edged, flat-top islands up to coverages θ=7.5 ML. The evidence is based on the spot profile analysis–low-energy electron diffraction diffracted intensity distribution as a function of k_‖, 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.