2003 Fiscal Year Final Research Report Summary
Ultra-fast Time-resolved Field-emission-current Measurements of Surface Adsobates on Si-tip
| Project/Area Number |
14550027
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
表面界面物性
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| Research Institution | Kyushu University |
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Principal Investigator |
MOTOOKA Teruaki Kyushu University, Materials Science and Engineering, Professor, 工学研究院, 教授 (50219979)
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| Project Period (FY) |
2002 – 2003
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| Keywords | Silicon / Molecular Dynamics / Liquid / solid Interface / Transition La yet / Field Emission |
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| Research Abstract |
We have carried out time-resolved measurements of field-emission currents from silicon tips. The ultra-fast spectroscopy has been carried out by a femtosecond field emission camera originally developed to observe single adsorbate dynamics on metal tips. As a preliminary observation of semiconductor surface dynamics, we have performed measurements in picosecond time resolution. Even though the maximum current in the present set-up is not enough to study the single atomic dynamics on silicon surfaces, one can gain information on collective motions of atoms and on electron tunneling from silicon surfaces. The maximum current density achieved in our study is comparable to those reached by solid state tunneling devices.
We have also investigated atomistic processes of nucleation and crystallization in supercooled liquid silicon (Si) based on molecular-dynamics (MD) simulations using the Tersoff potential. MD cells composed of up to 8192 Si atoms were heated to produce melted Si, and then melted Si was quenched under various supercooled conditions with or without a temperature gradient and the corresponding nucleation processes were visualized. The critical nucleation radius was determined as a function of the amount of supercooling ΔT and it was found to be inversely proportional to ΔT. It was also found, in the case of supercooling under a linear temperature gradient, that nucleation first occurred at the lower temperature region and then crystallization proceeded toward the high temperature region with the (111) surface mostly parallel to the temperature gradient.
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