2015 Fiscal Year Annual Research Report
Time-resolved observation of surface and interface structures
Publicly Offered Research
| Project Area | 3D Active-Site Science |
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| Project/Area Number |
15H01044
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| Research Institution | Tokyo Gakugei University |
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Principal Investigator |
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| Project Period (FY) |
2015-04-01 – 2017-03-31
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| Keywords | X線反射率 / X線回折 / 表面・界面 / 物性実験 / 時分割測定 |
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| Outline of Annual Research Achievements |
In the present research, an instrument for time-resolved measurements of the X-ray scattering from surfaces and interfaces is improved and applied to the in-situ observation of dynamical processes at surfaces and interfaces. This instrument can simultaneously observe the structure on the atomic scale and the nanometer scale with a time resolution of seconds or less.
The first topic that was addressed in FY2015 was the installation of two X-ray mirrors to suppress higher-harmonic X-rays. This worked as planned, speeding up the measurement improving the data quality.
The instrument was applied to the observation of structural changes in the photoconversion of organic semiconductor thin films. The nanometer-scale structure (density, thickness and roughness) and the crystallinity of the organic film was observed simultaneously in the experiment. In addition, the chemical state of the sample was also monitored by optical spectroscopy.
The structural evolution of an ionic liquid/electrode interface after a potential step was also investigated. By measuring the time-resolved X-ray reflectivity, evidence for slow structural relaxations that are not associated with charge flow was found.
In addition, research and test experiments to make it possible to use the present method with monochromatic X-ray sources were conducted. This should make it possible to use high intensity X-ray radiation from an undulator source.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
The measurement of the organic thin film samples proceeded as planned. In addition, research regarding the structure of an ionic liquid/electrode interface was also conducted, giving interesting results.
Regarding the improvement of the instrument, some changes to the plan had to be made. The X-ray mirrors worked as planned, but their preparation was more expensive than expected. For this reason, the planned new crystal bender could not be purchased.
A new sample cell was designed and purchased with which measurements of the optical reflection spectrum simultaneously to the X-ray scattering measurements are possible. This gives information about the chemical state of the sample in addition to the structure.
Finally, first steps toward extending the method to use high-intensity monochromatic X-rays were made, which is expected to improve the time resolution and data quality.
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| Strategy for Future Research Activity |
In FY2016, the measurement of samples from the 3D Active Sites Research Area, and the improvement of the instrument will be continued.
First, the observation of the photoconversion of organic semiconductor thin films will be extended to different sample thicknesses to obtain a more systematic understanding of the processes occurring during the photoconversion. The investigation of different organic molecules is also planned. The investigation of the structural evolution of ionic liquid/electrode interfaces will also be continued.
To improve the instrument, a new crystal bender for focusing the X-ray beam onto the sample will be designed and constructed. This is expected to improve the focus of the X-rays, making a more accurate measurement of even small samples possible.
In addition, the research to extend the present method to use monochromatic X-ray sources will be continued. In particular, experiments at SPring-8 are planned.
The development of a direct structure determination method will also continue.
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