Uniform Pb nanowires of magic thickness on Si(111) controlled by elastic interaction and quantum size effects

Abstract

An ordered array of uniform single crystal Pb nanowires with a magic thickness of 9 monolayers (ML) was obtained on Si(111) by a two-step method. The coverage of 6.4 ML is critical for the formation of uniform nanowires at the deposition temperature of 200 K and the flux rate of 1.2 ML/min, while at other coverages elongated islands or interconnected stripes with various thicknesses are formed. The width ratio of the nanowires to the Si(111) substrate terraces is found to be a characteristic value of 0.54. In situ low-temperature scanning tunneling microscopy study reveals that the magic thickness and uniform distribution of the Pb nanowires are governed by the interplay between the electronic quantum size effects along the normal direction and the lateral elastic interaction induced by strain.