Photoionization of the silicon divacancy studied by positron-annihilation spectroscopy

被引:36
作者
Kauppinen, H
Corbel, C
Nissila, J
Saarinen, K
Hautojarvi, P
机构
[1] Helsinki Univ Technol, Phys Lab, FIN-02015 Espoo, Finland
[2] CENS, Inst Natl Sci & Tech Nucl, F-91191 Gif Sur Yvette, France
关键词
D O I
10.1103/PhysRevB.57.12911
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
The optical ionization of the silicon divacancy in 2-MeV electron-irradiated Si was studied by using positron-lifetime and positron-electron momentum distribution measurements under illumination with monochromatic light. Upon irradiation at room temperature, negative and neutral divacancies are detected in both float zone and Czockralski Si by positron-annihilation measurements in darkness. The positron-annihilation characteristics of the divacancy are determined as tau(d)=300(5) ps = 1.35(2)x tau(b), S-d = 1.055(3) x S-b, and W-d = 0.75(2) x W-b. Illumination at 15 K with monochromatic 0.70-1.30 eV light has a strong effect on the positron trapping rate to the divacancies. The results can be understood in terms of optical electron and hole emission from the electron levels V-2(-l0) and V-2(2-l-) of the divacancy. The changes in the positron trapping rate are due to the different sensitivities of the positron to the charge states V-2(0), V-2(-), and V-2(2-). The spectral shape of the positron trapping rate under illumination reveals an electron level at E-u + 0.75 eV, which is attributed to the ionization level V-2(2-/-) of the divacancy.
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收藏
页码:12911 / 12922
页数:12
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