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.