Reflectance anisotropy during growth of Pb nanowires on well ordered Si(3 3 5) surface

Ultrathin Pb films on Si(3 3 5) deposited at temperatures ranging from 105 to 305 K are investigated by optical reflectance method, scanning tunneling microscopy, and reflection high energy electron diffraction. From the reflectance data for light with photon energy of 0.6 eV, the imaginary part of the Pb dielectric function ε2Pb is determined. For films with coverages below about 2 monoatomic layers (ML), independent on the substrate temperature, ε2Pb linearly increases with the average film thickness. For larger Pb coverages, it strongly depends on the deposition temperature. The observed variation of the dielectric function is correlated with structural and topographic transitions of Pb ultrathin films growing on Si(3 3 5) surface. The origin of the optical anisotropy as a consequence of self-assembling of Pb nanowires on well ordered Si(3 3 5) substrate is discussed.