期刊
JOURNAL OF APPLIED PHYSICS
卷 107, 期 11, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.3427539
关键词
ab initio calculations; copper compounds; gallium compounds; indium compounds; mass spectroscopy; semiconductor thin films; surface reconstruction; ternary semiconductors; X-ray emission spectra; X-ray photoelectron spectra
资金
- European Commission [019670]
The surface Cu-depletion of chalcopyrite thin films and its influence on the interface properties of related solar cells have been subject of a controversial debate for many years. Although the nature of this Cu-depletion and its extension in depth are crucial for the device physics, there are only a few contradictory experimental results that address this topic. To clarify this issue, we performed depth-dependent compositional analysis by angle dependent soft x-ray emission spectroscopy (AXES) on Cu(In,Ga)Se-2 thin films with different integral Cu-contents. By considering depth profiles from literature and by taking the accuracy of AXES into account, our numerical AXES simulations predict a pronounced angle dependence for our samples. However, our experimental data show only a minor angle dependence, which leads to the conclusion that the Cu-depleted surface layer must be restricted to a very thin surface layer, which is not accessible by AXES. This conclusion is consistent with the result from our previous investigation by hard x-ray photoelectron spectroscopy, where we found a Cu-depleted surface layer in the subnanometer regime. Consequently the present study gives further experimental evidence for the surface reconstruction model proposed by first-principles calculations. Supported by secondary neutral mass spectroscopy, we show that the minor angle dependence in our AXES data can be attributed to a Ga-gradient in the chalcopyrite material. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3427539]
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