1. Status of Beamline BL07LSU at SPring-8
The University-of-Tokyo high-brilliance synchrotron soft X-ray outstation beamline
BL07LSU at SPring-8 has been maintained by the permanent staff members with adjuncts
for user operations. The scientific aim of the beamline is to promote advanced
spectroscopy for solid state and soft (including bio-) materials. There are four regular
endstations for time-resolved soft X-ray spectroscopy (TR-SX spectroscopy), ambientpressure X-ray photoelectron spectroscopy, 3D-scanning photoelectron microscope (3Dnano-ESCA) and high-resolution soft X-ray emission spectroscopy (HORNET) that areopen for users. There is also a free port station for users who bring their own experimental
apparatus.
The beamline BL07LSU is equipped with a segmented cross-type undulator. By using
phase shifter among the undulator segments, a polarization control of soft X-ray wasstarted since 2016. Circularly and linearly polarized soft X-rays at full energy range (250– 2000 eV) have been available by tuning the permanent magnet type phase shifter.
At the endstations, various scientific researches were carried out by both the laboratory
staffs and general users (G-type and S-type applications). In addition, from this fiscal year,
we started to accept priority issues (P type problem) for the purposes of utilizing theadvanced synchrotron radiation light source technology, especially high-speed
polarization switching, at BL07LSU and of promoting developments of the beamline andendstation technologies for the next generation synchrotron light source.
Recent activities at each station is briefly introduced below.
(1) Time-Resolved soft X-ray spectroscopy station (TR-SX spectroscopy)
The station is to perform time-resolved photoemission spectroscopy experiments bysynchronizing the high-brilliant soft X-ray and the ultra-short laser pulses. A twodimensional angle-resolved time-of-flight (ARTOF) analyzer has been equipped for theefficient time-resolved measurements and the measurement temperature can be controlledfrom 15 K to 1150K. The station adopts two different optical laser systems synchronizedwith synchrotron soft X-ray; low repetition rate and high pulse energy (1 kHz, mJ) andhigh repetition rate and low pulse energy (208 kHz, J).
In 2019, Hayashi group succeeded in observing the temporal variation of the Si 2p
photoelectron diffraction pattern of a silicene layer after the laser pulse irradiation. The
time-resolved pattern agreed with the simulation results and revealed the lattice dynamics.
The research paper is submitted as the world's first time-resolved photoelectron
diffraction data. The system of time-resolved photoelectron spectroscopy will betransferred to Kashiwa Campus in 2020 for experiments with the vacuum ultraviolet/soft

X-ray lasers. The time-resolved photoemission measurement will be continued users with
the AP-XPS system, see the following section, that has been updated for this purpose
recently.
(2) Ambient-pressure X-ray photoelectron spectroscopy (AP-XPS)
AP-XPS station allows Operando observation of catalysts under reaction conditions.
The AP-XPS station was constructed in 2014 by an external funding (JST ACT-C project),
and was opened to external users since 2018. The AP-XPS system is equipped with adifferentially pumped electron analyzer (SPECS, PHOIBOS 150 NAP) and an ambientpressure gas cell. XPS measurements can be performed both under ultrahigh vacuum andin near-ambient gas pressure up to 20 mbar. Catalytic activity is monitored by mass
spectrometer, and simultaneous evaluation of adsorbate and catalyst electronic states isperformed. In addition to the experiments using synchrotron soft X-ray, off-line
experiments using a twin-anode X-ray source can be performed.
In 2019, a variety of research projects have been conducted using the AP-XPS station:(i) Methanol synthesis on Cu-Zn catalysts, (ii) Sabatier reaction on Ni catalysts, (iii) H2adsorption/absorption in Pd nanoparticles and Pd alloys (PdAg and PdCu), (iv) CH4partial oxidation on Pd catalysts, (v) CO2 adsorption on graphene support, (vi) bandalignment at a semiconductor photoelectrode and electrolyte interface, and (vii)development of time-resolved AP-XPS. Koitaya et al. published a research paper on CO2hydrogenation on a Zn modified Cu surface in ACS Catalysis (IF 11.384). Tang et alreported articles on H2 adsorption and storage on a PdCu alloy surface in Appl. Surf. Sci.
(3) 3D-scanning photoelectron microscope (3D nano-ESCA)
3D-nano-ESCA can be used for sub-100 nm range microscopic 2D mapping and depth
profile of the chemical structure of functional materials and devices.
In 2019, elucidation of facet-wise Li de-insertion characteristics of LTO in all-solidstate LIB was carried out as a joint research by Asakura and Hosono group at AIST. Bychanging the solid electrolyte from LLZ and dry polymer to sulfide solid electrolyte, thedegas rate was reduced, and a clearer image was obtained. Also conducted wasphotoelectron spectromicroscopy of SnS as a joint research by Nagamura at NIMS andProf. Nagashio group at UTokyo. The reason behind the monolayer growth of SnS by thesimple PVD remains unclear. A single SnS film was not grown from high-purity SnSpowder. By nano-ESCA observation, it is confirmed that the lateral growth of monolayer
SnS is facilitated due to the enhanced surface diffusion of SnS precursor molecules by
Sn2S3 contaminants in low-purity powder. Lastly, super-resolution imaging and depth
profiling analysis of hetero-junction transistor fine structures using III-V compoundsemiconductors were performed as a joint research by Fukidome group at Tohoku Univ.
In the viewpoint of measurement informatics, sparce modeling approach is applied toovercome the limits of spatial resolution and make it possible to observe objects in thesize of several nms.
(4) Ultra high-resolution soft X-ray emission spectroscopy (HORNET)
The station is dedicated for soft X-ray emission (or resonant inelastic X-ray scattering:RIXS) spectroscopy measurements with high-resolution (E/ΔE > 10,000) and undervarious environmental conditions (gas, liquid, and solid).
In 2019 the station accepted 19 joint researches. Studies on solid state physics includei) O K-edge RIXS of holes doped in Pr1.4-xLa0.6CexCuO4, ii) Observation of magnoninduced state of spintronics material Y3Fe5O12 by operando RIXS by application of highfrequency electromagnetic wave, iii) XAS and RIXS studies of the electric-field-induced
metal insulator transition of Ca3(Ru1-xTix)2O7, iv) Fe L-edge RIXS of diluted magnetic
semiconductors (Ga, Fe)Sb and (In, Fe)As. For the battery and catalyst materials, thevalence state of Li-ion battery electrode materials LiMn1-xFexPO4 and Li(Li2/3, Mn4/3)O4during charge and discharge as well as water decomposition catalyst CoxFeyO4 wereobserved by operando RIXS. For the studies on the behavior of interfacial water, water
hydrating thermo-responsive polymer PNIPAM, polyvinyl alcohol aqueous solution,water confined in a subnanopore of liquid crystalline membrane, interfacial water in thepolymer-brush form of PBuA and PMEA were observed. All the measurements weresuccessful in the determination of specific hydrogen bond structure of water responsible
for materials functions such as phase transition, folding, ice nucleation process, water
filtration, and biocompatibility.