X-ray standing-wave measurements on Cs and Rb adlayers on the Si(111)7 X 7 surface are presented. Low [almost-equal-to 0. 06 monolayer (ML)] and medium (almost-equal-to 0. 15 ML) coverages have been analyzed. The (111) and the (111BAR) reflections have been used. Since the experimental results clearly indicate that multisite occupancy takes place, the threefold hollow (H-3), the threefold filled (T4), and all the dangling-bond sites have been considered as possible adsorption sites. Distinction has been made between the faulted and the unfaulted half of the 7 X 7 cell. The Si-alkali-metal bond length has been assumed to be the sum of the covalent radii of the two elements. Our results indicate that both Rb and Cs adsorb preferentially on the H-3 and the T4 sites. The remaining atoms adsorb most at the atop sites for Rb and at the adatom sites (i.e., on top of the silicon adatom) for Cs.
STRUCTURAL STUDY OF THE SI-ALKALI-METAL INTERFACE WITH X-RAY STANDING WAVES
GIANNINI C;
1992
Abstract
X-ray standing-wave measurements on Cs and Rb adlayers on the Si(111)7 X 7 surface are presented. Low [almost-equal-to 0. 06 monolayer (ML)] and medium (almost-equal-to 0. 15 ML) coverages have been analyzed. The (111) and the (111BAR) reflections have been used. Since the experimental results clearly indicate that multisite occupancy takes place, the threefold hollow (H-3), the threefold filled (T4), and all the dangling-bond sites have been considered as possible adsorption sites. Distinction has been made between the faulted and the unfaulted half of the 7 X 7 cell. The Si-alkali-metal bond length has been assumed to be the sum of the covalent radii of the two elements. Our results indicate that both Rb and Cs adsorb preferentially on the H-3 and the T4 sites. The remaining atoms adsorb most at the atop sites for Rb and at the adatom sites (i.e., on top of the silicon adatom) for Cs.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
