Early stages of cesium adsorption on the As-rich c(2x8) reconstruction of GaAs(001): Adsorption sites and Cs-induced chemical bonds
|Title||Early stages of cesium adsorption on the As-rich c(2x8) reconstruction of GaAs(001): Adsorption sites and Cs-induced chemical bonds|
|Publication Type||Palaiseau Article|
|Author Address|| |
Hogan, C (Reprint Author), Univ Roma Tor Vergata, Dipartimento Fis, I-00133 Rome, Italy. Univ Roma Tor Vergata, Dipartimento Fis, I-00133 Rome, Italy. Univ Roma Tor Vergata, INFM, I-00133 Rome, Italy. Ecole Polytech, Phys Mat Condensee Lab, F-91128 Palaiseau, France. Ctr Univ Paris Sud, LURE, CNRS, MR,CEA, F-91898 Orsay, France. Univ Milan, Dipartimento Fis, I-20122 Milan, Italy. Univ Milan, INFM, I-20122 Milan, Italy. Ecole Polytech, CEA, CNRS, UMR 7642,Lab Solides Irradies, F-91128 Palaiseau, France. Univ Modena, Dipartimento Fis, I-41100 Modena, Italy. Univ Modena, INFM, I-41100 Modena, Italy.
|Hogan, C, Paget, D, Garreau, Y, Sauvage, M, Onida, G, Reining, L, Chiaradia, P, Corradini, V|
|Publisher||AMERICAN PHYSICAL SOC|
|Year of Publication||2003|
|Journal||Phys. Rev. B|
We investigate the adsorption of Cs on the As-rich c(2x8)/(2x4) reconstruction of GaAs(001) at low coverages using a combination of theoretical and experimental techniques. Density-functional-theory local-density-approximation total-energy calculations and x-ray diffraction experiments find only minimal Cs-induced surface relaxation and identify three preferential adsorption sites within the partially disordered overlayer. These sites are, in order of decreasing occupation probability, the arsenic dimer bridge D site, the gallium dangling bond T-2(') site, and the arsenic T-3 trench site. Detailed analysis of the wave functions and electronic charge densities allows us to clarify the bonding mechanisms at the three sites. At the gallium site, the bonding is strongly ionic and involves significant charge transfer to a new Cs-induced state reminiscent of the p(z) orbital of the gallium atom in the sp(2) configuration. In sharp contrast, at the arsenic sites, the charge transfer is minimal and the bonding rather occurs through mixing with a relatively delocalized state of the clean surface. The ionization energy decreases are estimated and compared for the three sites.