Dynamical resonant charge transfer of fast C-, O-, F- ions and water covered Si(111) surface

作者：Xiong, Feifei; Gao, Lei; Liu, Yuefeng; Lu, Jianjie; Liu, Pinyang; Qiu, Shunli; Qiu, Xiyu; Guo, Yanling; Chen, Ximeng; Chen, Lin^*

来源：Vacuum, 2017, 137: 23-30.

DOI：10.1016/j.vacuum.2016.12.008

• MICROCHANNEL PLATE DETECTOR
• PROJECTED BAND-GAP
• ELECTRON-CAPTURE
• NEGATIVE-IONS
• H-FORMATION
• HYDROGEN-IONS
• AUGER NEUTRALIZATION
• GRAZING SCATTERING
• SILICON SURFACES
• AL(111) SURFACE

The experiment of 6.5-22.5 keV C-, O- and F- ions scattering on water covered Si(111) surface has been performed. It is found that the positive-ion fraction is very low and increases monotonically as a function of perpendicular exit velocity and exit angle. In particular, the negative-ion fraction increases monotonically with perpendicular exit velocity for specular scattering, and for a given incident energy the angle dependence of the fraction is nonmonotonic. We interpret the observed positive ions in terms of inelastic binary collision, and adopt a modified resonant charge transfer model to calculate the bell shaped negative-ion fraction. We find that the neutral yield at short ion-surface distance is nonzero and obeys well an exponential dependence. It strongly indicates that a dynamical equilibrium for negative ion formation is never achieved at short distances, and the band gap effect on charge transfer can be neglected to a large extent in this relatively high energy region.

• 出版日期2017-3
• 单位兰州大学