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題 名 | Surface and Bulk Photoemission: Some Old Problems and New Findings |
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作 者 | Chiang,T. C.; | 書刊名 | Chinese Journal of Physics |
卷 期 | 35:4 1997.08[民86.08] |
頁 次 | 頁496-508 |
分類號 | 330 |
關鍵詞 | |
語 文 | 英文(English) |
英文摘要 | Angle-resolved photoemission has been applied to a variety of materials for electronic structure determination. It is generally regarded as a routine technique. Yet the measured lineashapes are often much more complicated than simple Lorentzians riding on a smooth background as is usually assumed. This study is a reexamination of the photoemission properties of Ag and Cu. These are simple metals for which the standard models are expected to work well. Yet the measured peaks are significantly asymmetric, and the "background" shows interesting variations as a functions of photon energy. These "nonideal" behaviors have been known for almost twenty years, but there has been no satisfactory explanation. This work showns that the underlying physics is related to a ▽. A term in the optical transition matrix element, which has been largely ignored in the past. This term has a significant contribution near a surface due to a rapid change in dielectric response. An analysis incorporating this surface term explains the observed lineshape features. A test employing an overlayer to modify the surface boundary condition provides a direct proof of the surface origin of these effects. It is thus important to consider the electromagnetic response of a surface for a complete understanding of the photoemission process. PACS. 79.60.Bm-Clean metal, semiconductor, and insulator surfaces. PACS. 71.20.Gj-Other metals and alloys. PACS. 73.20.At-Surface states, band structure, electron density of states. |
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