Energy spacing between electronic resonances: A physical quantity correlating to diverse phases of the dense Pb overlayers on Si(111)

The unoccupied states of Pb dense overlayers on Si(111) reveal an oscillatory character with two electronic resonance peaks that can be observed by scanning tunneling spectroscopy. By measuring the energy spacing between resonance peaks, it is found that the energy spacing is reduced with increasing the coverage of dense overlayer. The change of energy spacing originates from that the movement of the high-energy resonance peak is more pronounced than that of the low-energy peak with varying coverage. The authors demonstrate that this phase-dependent energy spacing is a useful quantity to identify that the room-temperature 1 x 1 and the low-temperature root 7 x root 3 phases have an identical coverage of 1.2 ML. (C) 2014 American Vacuum Society.