An effect of vicinal surface morphology on adsorbate structure: Yb growth on [1 1 2]-tilt Si(1 1 1)

We have investigated the growth of ytterbium (Yb) on vicinal, step-bunched Si(1 1 1) surfaces miscut 3.8° and 5.3° toward the [1 1 2] direction in the coverage range of 0–0.17 monolayers by room temperature scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). The ordering of the adsorbed layer is found to depend drastically on a terrace width. STM shows 3×2-Yb reconstruction on 3.8°-tilt substrate, while LEED exhibits (3×1) periodicity for this Yb-covered surface. Using a step correlation function and terrace width distribution measurements, formation of this ordered phase is shown to be accompanied by varying kinetic step parameters and elastic step–step interaction. In contrast, Yb is observed to form no ordered adsorbate structures on 5.3° cut-off Si(1 1 1) surface. Due to a higher step density, a relief of surface stress is proposed for this surface. The stress relief is suggested to be a reason why the Yb overlayer does not remove a 7×7 unit cell on terraces of 5.3°-tilt substrate. Moreover, an existence of critical value of terrace width for creation of Yb-induced reconstructions on [1 1 2]-miscut Si(1 1 1) is reported.