科研之友
微信
新浪微博
Facebook
分享链接
摘要
The adsorption of K and I on the surface of the high-T-c cuprate BSCCO-2212 is investigated with low-energy (0.8 to 2 keV) Na+ ion scattering and density functional theory (DFT). Samples were cleaved in ultrahigh vacuum and charge-resolved spectra of the scattered ions were collected with time-of-flight. The spectra contain a single peak representing Na scattered from Bi, as the clean surfaces are terminated by BiO. The neutralization of scattered Na depends on the local potential above the target site, and the angular dependence indicates that the clean surface has an inhomogeneous potential. Neutralization is dependent on the coverage of I, but independent of K adsorption. DFT suggests high-symmetry sites for the adsorption of both I and K, and that the potential above the Bi sites is altered by I by an amount consistent with the experimental findings, while the potential is not affected by K adsorption. DFT also enables an experimental determination of the "freezing distance," which is the effective point beyond which charge exchange does not occur, to be 1.6 +/- 0.1 angstrom from the outermost Bi layer.
- 出版日期2010-1
