Formation of an intermediate 3 × 3 phase from Pb on Si(111) at high temperature

Abstract

Using high-resolution spot-profile-analysis low-energy electron diffraction (SPA-LEED) we have investigated low-coverage phases of Pb on Si(111) in the temperature range between 25 °C and 600 °C. After the annealing of 1/3 of a monolayer (ML) of Pb on Si(111) at 500 °C and cooling the sample down to room temperature, we observe a 3 × 3 phase beside the well known Pb/Si(111)(3)1/2 × (3)1/2R30° structure. The 3 × 3 phase is poorly ordered (domain size 20 Å-40 Å) compared to the (3)1/2 × (3)1/2 phase (domain size 1000 Å) as we conclude from profile analysis of the diffraction spots. The development of the 3 × 3 superstructure with increase of the annealing temperature was monitored and we observe a change of the domain size from 20 Å up to 40 Å upon annealing at 500 °C and 540 °C, respectively. After annealing at 580 °C the 3 × 3 phase has vanished and we detect only the (3)1/2 × (3)1/2 mosaic phase.