Adsorbate structure and vibrations on the Bi/Si(001)-(1 × 2) surface

Abstract

X-ray standing wave measurements were undertaken to determine the bonding position and vibrational amplitude (normal to the surface plane) of Bi ad-dimers on the Bi-saturated Si(001)-(1 × 2) surface. Using the (004) Bragg reflection, we find that the center of the Bi ad-dimers lies 1.72 Å above the bulk-like Si(004) surface atomic plane. Using the (008) Bragg reflection, we find that the room temperature root-mean-square vibrational amplitude of the Bi adatoms normal to the surface plane is 0.13 Å. This direct determination of the adsorbate vibrational dynamics verifies earlier assumptions regarding the magnitude of adsorbate surface vibrations on Si surfaces, and suggests that the vibrational amplitude of dimerized group V/Si(001)-(1 × 2) structures is independent of the mass of the adsorbate.