[en] Simultaneous measurements of picosecond time-resolved synchrotron-radiation (SR) X-ray diffraction and femtosecond time-resolved visible absorption were performed at BL40XU beamline of SPring-8 on two films of Co-Fe cyanides, Na_0.77Co[Fe(CN)₆]_0.902.9H2_O (NCF90) and Na_0.16Co[Fe(CN)₆]_0.713.8H₂O (NCF71). The simultaneous measurements unambiguously revealed that the photoinduced charge transfer between the Co and Fe sites causes uniform volume expansion/contraction within 100 ps. The photoinduced lattice contraction observed in the NCF71 film can be interpreted in terms of the photoinduced formation of a hidden metastable phase. (author)

[en] Anomalous lattice shrink is observed in a single submicrometer-sized CeO₂ particle with X-ray diffraction using an optical-trap sample holder. A CeO₂ particle 380 nm in size is successfully levitated with radiation pressure force exerted by counterpropagating laser beams and irradiated by a high-flux focused synchrotron radiation beam. The diffraction pattern of a single particle is consistent with that of CeO₂ but the lattice shrink approaches 1.22% of the lattice constant of a particle assemblage. (author)

[en] A time-resolved structural investigation of the data storage process in a digital versatile disk (DVD) or Blu-ray disk media is desired for better understanding of the fast phase-change mechanism for designing a higher performance optical recording material. Thus, the development of an in situ structural observation technique at the picosecond level has been carried out for the investigation of the fast phase-change phenomena using synchrotron radiation pulsed X-rays and synchronized femtosecond laser irradiation. Then, for Ge₂Sb₂Te₅ (GST) and Ag_3.5In_3.8Sb_75.0Te_17.7 (AIST), the technique has been applied to a snapshot of X-ray diffraction pattern in the nanosecond crystallization process from the amorphous to the crystal phase, which corresponds to the erasing process of the DVD recording system. The key to success of the time-resolved experiment was to optimize the measurement timing system efficiency for both sufficient counting statistics, i.e., counting quantity and precision of time resolution, i.e., counting quality. Our time-resolved experimental system has sufficient accuracy, so that our previous study showed a significant difference in the crystal growth process between GST and AIST, indicating that the crystal growth process is key to fast phase change. To increase the precision of data in terms of signal-to-noise ratio and counting statistics, we developed a highly repetitive pump-probe measurement system combined with an X-ray microbeam technique providing high counting quantity, and used it to demonstrate a snapshot of an X-ray diffraction profile of GST. The measurement system has a time resolution of 50 ps and a 1 kHz repetition rate. Our development of the technique to take a snapshot for the structural visualization of phase-change phenomena with the time-resolved microbeam X-ray diffraction is described. (author)

[en] The X-ray microbeam diffraction from each particle leads to a deeper structural characterization, i.e. inter-particle structural fluctuation, of powdery compound. Here, we performed X-ray microbeam diffractions of Na_xCo_1−zNi_z[Fe(CN)₆]_y at BL40XU beamline of SPring-8. In the whole region of z, the inter-particle structural fluctuation is negligible in the as-grown powder. We found that the average (d-bar₀-bar₁-bar₂-bar) of the spacing (d₀₁₂) of the (012) plane decreases with X-ray irradiation time (t). The standard deviation (σ) of d₀₁₂ steeply increases with t from 0.006 Å at t = 1 s to 0.031 Å at t = 60 s, indicating that inter-particle structural fluctuation is induced by the X-ray irradiation. (author)

[en] A high-precision diffractometer has been developed for the structure analysis of a submicrometer-scale single grain of a powder sample at the SPring-8 BL40XU undulator beamline. A stable focused synchrotron radiation beam with the phase zone plate and a low eccentric goniometer are the key techniques for measuring accurate diffraction intensity data of a submicrometer-scale single powder grain. In order to verify the performance of the diffractometer, the diffraction pattern data of several submicrometer-scale BaTiO₃ grains, with dimensions of 600 x 600 x 300 nm, were measured. By identifying the diffraction data set of one single powder grain, the crystal structure was successfully determined. The features of the high-precision diffractometer and the result of the structure analysis of a submicrometer-scale BaTiO₃ single powder grain are described. (author)

[en] The pulse characteristic and high coherent x-ray beam of SPring-8 allow us to investigate dynamics of chemical reactions and phase transition of materials caused by applied field. In order to realize such direct investigation, 'x-ray pinpoint structural measurement', which is the advanced x-ray measurement technique in nanometer spatial scale and/or pico-second time scale, is being developed at SPring-8. The features of 'x-ray pinpoint structural measurement' technique are, 1) spatial resolution: ∼ 100 nm, 2) time resolution: ∼ 40 ps, and 3) measurement under the photo-irradiation, electric field, magnetic field, high pressure and active devices. Using this technique, we will explore the novel concept and new phenomena for nanomaterials and/or devices, and also demonstrate their validity

[en] Submicrometer single crystal diffractometry for highly accurate structure determination was developed using the extremely stable and highly brilliant synchrotron radiation from SPring-8. This was achieved using a microbeam focusing system and the submicrometer precision low-eccentric goniometer system. We demonstrated the structure analyses with 2x2x2 μm³ cytidine, 600x600x300 nm³ BaTiO₃, and 1x1x1 μm³ silicon. The observed structure factors of the silicon crystal were in agreement with the structure factors determined by the Pendelloesung method and do not require absorption and extinction corrections.

[en] We have developed a pump-probe X-ray diffraction measurement system for a sample with irreversible reaction at BL40XU in the SPring-8. The system mainly consists of a time-resolved measurement system, a sample disk rotation system, and an X-ray microbeam system. The time-resolved measurement system gives time resolution of 50 ps in laser-pump and X-ray probe method. A sample disk rotation system for repetitive measurements was made to give a virgin sample for every measurement. The number of repetitions for one sample disk was increased by using the X-ray microbeam technique. To keep the overlap of the X-ray microbeam and the laser beam on the sample surface during the disk rotation, the sample disk rotation system was constructed by a low-eccentric spindle motor. By using this system, the pump-probe X-ray diffraction measurement was demonstrated for a crystallization process of a DVD material.

[en] We have developed a system of laser-pump and synchrotron radiation probe microdiffraction to investigate the phase-change process on a nanosecond time scale of Ge₂Sb₂Te₅ film embedded in multi-layer structures, which corresponds to real optical recording media. The measurements were achieved by combining (i) the pump-laser system with a pulse width of 300 ps, (ii) a highly brilliant focused microbeam with wide peak-energy width (ΔE/E ∼ 2%) made by focusing helical undulator radiation without monochromatization, and (iii) a precise sample rotation stage to make repetitive measurements. We successfully detected a very weak time-resolved diffraction signal by using this system from 100-nm-thick Ge₂Sb₂Te₅ phase-change layers. This enabled us to find the dependence of the crystal-amorphous phase change process of the Ge₂Sb₂Te₅ layers on laser power.

[en] Brilliant pulsed x-ray synchrotron radiation (SR) is useful for pump-probe experiment such as time-resolved x-ray diffraction, x-ray absorption fine structure, and x-ray spectroscopy. For laser pump-SR x-ray probe experiments, short pulsed lasers are generally synchronized to the SR master oscillator controlling the voltage for acceleration of electron bunches in an accelerator, and the interval between the laser and the SR pulses is changed around the time scale of target phenomenon. Ideal delay control produces any time delay as keeping the time-precision and pointing-stability of optical pulses at a sample position. We constructed the time delay control module using a continuous phase shifter of radio frequency signal and a frequency divider, which can produce the delayed trigger pulses to the laser without degradation of the time precision and the pointing stability. A picoseconds time-resolved x-ray diffraction experiment was demonstrated at SPring-8 storage ring for fast lattice response by femtosecond pulsed laser irradiation, and suggested the possibility of accurate sound velocity measurement. A delay control unit operating with subpicosecond precision has also been designed for femtosecond pump-probe experiments using a free electron laser at SPring-8 campus.