1999 Fiscal Year Final Research Report Summary
Study of photo-induced atomic processes on semiconductor surfaces by means of femtosecond spectroscopy
| Project/Area Number |
09440115
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅰ(光物性・半導体・誘電体)
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| Research Institution | Nagoya University |
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Principal Investigator |
TANIMURA Katsumi Graduate School of Science, Nagoya University, Professor, 大学院・理学研究科, 教授 (00135328)
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| Co-Investigator(Kenkyū-buntansha) |
AKIMOTO Ikuko Graduate School of Science, Nagoya University, Research Associate, 大学院・理学研究科, 助手 (00314055)
ITOH Chihiro Graduate School of Science, Nagoya University, Research Associate, 大学院・理学研究科, 助手 (60211744)
KANASAKI Junichi Graduate School of Science, Nagoya University, Research Associate, 大学院・理学研究科, 助手 (80204535)
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| Project Period (FY) |
1997 – 1999
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| Keywords | reconstructed surface / desorption / photo-induced structural changes / STM / femtosecond spectroscopy |
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| Research Abstract |
The purpose of this project is to make clear the microscopic processes of laser-induced electronic instability on clean semiconductor surfaces. The surfaces of Si(111)-(7x7) and InP(110)-(1x1) in an UHY chamber were excited either by fs-laser pulses for dynamical study or by ns- laser pulses for spectroscopy. Structural changes induced were studied by direct imaging of the atomic structures by scanning tunneling microscope (STM) and by high-sensitive detection of desorbed neutral species. Main results obtained in this project are summarized below.
1) On Si(111)-(7x7), which is a proto-typical example of reconstructed semiconductor surfaces, laser-induced electronic instability is induced by the surface-specific electronic transition at 2.0 eV, followed by non-linear localization to induce bond breaking of adatoms on the surface. Two-hole localization followed by the phonon-kick process has been proposed to be the origin of the instability.
2) On InP(110)-(1x1), which shows quasi-one dime
… More
nsional atomic and electronic properties, similar laser-induced electronic instability is induced, but with strongly wavelength-dependent morphologies in structural changes. Upon exciting surface specific transitions, P-vacancy strings are generated along [110] direction, while two-dimensional vacancy islands are developed upon bulk-electronic excitation. These characteristics can be ascribed to different properties of photo-generated excited species in surface states and in bulk electronic states ; the former shows one-dimensional nature, while the latter is isotropic in mobility.
3) For studying desorption induced as a result of surface-structural changes, we successfully developed a new method of femtosecond non-resonant ionization spectroscopy (FNRIS) for detecting several neutral species simultaneously with high sensitivity. This method was applied for InP surfaces to show that desorption processes are also strongly super-linear with respect to the excitation intensity, similarly to the case of vacancy formation on the surface. Also, primary product of desorption has been confirmed to be monoatomic P and In atoms for clean (1x1) surface, being consistent with STM observation. Our results obtained in this project is the first demonstration of FNRIS to be a powerful tool for studying desorption from compound semiconductor surfaces. Less
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