Quantum growth of a metal/insulator system: Lead on sapphire

We report the observation of quantum growth behavior in a metal-on-insulator system. Using insulating substrates, with their large band gaps, should maximize quantum confinement effects. In a study of Pb film growth and thermal processing on sapphire, we have observed robust preferred island height selection over a wide thickness range-a hallmark of quantum confinement effects-up to 250 degrees C. By contrast, room temperature is the limit for Pb films prepared on Si(111). These results provide the evidence connecting the quantum growth behavior of overlayers with the substrate band gap. (C) 2010 American Institute of Physics. [doi:10.1063/1.3526727]