Quantum Size Effects in Low-Temperature Growth of Pb Islands on Si(111)7×7 Surfaces

Abstract

Flat-top Pb islands with critical and magic thickness have been observed in the Pb/Si(111)7 × 7 system at 200 K by scanning tunneling microscopy. The growth behavior, different from that in the Stranski-Krastanov mode, arises from a quantum size effect. Quantized states are detected in the current-voltage (I -V ) spectra on the Pb islands of varying thickness. Our observation of asymmetrical and oscillatory relaxation in the island thickness reveals that the charge distribution of confined electrons can influence the interlayer spacing. A simple model based on the infinite potential well can explain well all of our results.

Self-consistent study of electron confinement to metallic thin films on solid surfaces

“…Our finding is that the method overestimates the distance between the confinement barriers. This may explain the large values 11,[21][22][23] obtained by this scheme in comparison to other experiments. [7][8][9] The reason for this disagreement is the basic fact that Eqs.…”

“…There are also recent STS measurements of QWS's in the Pb layers on Si(111). 11,20,21 In these studies the overlayers are thinner and the QWS energy range is smaller than in the Pb/Cu(111) measurements by Otero et. al.…”

“…There are also recent STS measurements of QWSs in Pb layers on Si͑111͒. 11,21,22 The effective thickness of the Pb overlayer is then obtained by fitting the energy differences of the consecutive states. This is not very accurate and, in fact, there are contradictory results in the literature on the thickness of the wetting layer, ranging from 1 ML ͑Refs.…”

“…7-9͒ to 3 ML. 10,11,21,22 Our aim is to develop the formalism for the determination of confinement barriers in order to resolve the dilemma of these measurements of Pb on Cu or Si substrates.…”

“…This is not very accurate and there are contradictory results for the thickness of the wetting layer, ranging from 1 ML 7,8,9 to 3 ML. 10,11,20,21 There are several theoretical works based on the density functional theory (DFT) devoted to study QSE in thin films.…”