| 研究課題/領域番号 |
23K17150
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| 研究機関 | 大学共同利用機関法人高エネルギー加速器研究機構 |
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研究代表者 |
Ahmed Rezwan 大学共同利用機関法人高エネルギー加速器研究機構, 物質構造科学研究所, 博士研究員 (90900291)
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| 研究期間 (年度) |
2023-04-01 – 2026-03-31
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| キーワード | positron diffraction / surface / lepd / 2D materials / ultra-high vacuum |
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| 研究実績の概要 |
Research purpose is to build and establish a low-energy positron diffraction (LEPD) ultra-high vacuum (UHV) experimental station at KEK for the accurate determination of surface atomic structures. Although theoretically LEPD has shown interesting phenomenon for accurate surface structure determination but experimentally not verified.
Last fiscal year we prepared the experimental station which has enabled to conduct actual LEPD experiments for surface structure determination. We conducted the 1st experiment on Cu(001) surface and showed that the LEPD diffraction pattern is much more simple and portraying sharper Bragg peaks which gave much improved agreement with the theoretical data.
Now we have the plan to accurately determine complex 2D atomic structures using the new LEPD station.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
We have built the LEPD experimental station and conducted our first experiment on Cu(001) surface. We have obtained a very simple LEPD diffraction pattern which signifies less multiple scattering with sharper and simple Bragg peaks compared to the conventional low-energy electron diffraction (LEPD). We have also checked the multi-probe experimental facility in our system where we successfully transferred the clean Cu(001) sample from LEPD station to beamline-13B for ARPES measurement. Now we can do multi-beam experimental analysis for determining the surface and its band structure.
The intensity of positrons obtained from linac in KEK showed some fluctuations during the experiment due to some connection fault of the magnetic coils. Later it was identified and the operation is now smooth.
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| 今後の研究の推進方策 |
In this research my plan is to determine the 2D structure of Pb atoms (plumbene) on Pd(111) surface. Plumbene shows very interesting physical characteristics so accurate structure determination is necessary. Pb is a heavy atom (higher atomic number) which shows complex scattering factor and difficult to be determined by conventional LEED analysis.
We already successfully prepared Cu(001) sample and determined the structure very accurately and showed that LEPD has simple diffraction curve with less multiple scattering.
Therefore we want to prepare the plumbene on Pd(111) surface at the preparation chamber and determine the surface structure using LEPD. Later we want to transfer the prepared sample using portable UHV chamber to the beamline 13B in PF for ARPES measurement.
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| 次年度使用額が生じた理由 |
In this fiscal year we need to do some maintenance of the sample holder receiver and grabber attached to the transfer rod for transferring the sample from preparation chamber to LEPD chamber. The initial design of the grabber is "twisted type" which sometimes got stuck when transferring the sample from the sample holder receiver connected to the manipulator. The spring of the sample holder receiver will also be adjusted so that the contact between the sample holder and the receiver plate is firmly attached.
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