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. A scientific aim of the beamline is to promote advanced spectroscopy
for solid state and soft (including bio) materials. There are four regular endstations: timeresolved soft X-ray spectroscopy (TR-SX spectroscopy), soft X-ray diffraction, 3Dscanning photoelectron microscope (3D nano-ESCA) and ultrahigh resolution soft X-rayemission spectroscopy (HORNET) that are open for users. There is also a free port station
for users who bring their own experimental apparatus. In 2018, we have completedcommissioning of the ambient pressure X-ray photoelectron spectroscopy station at thefree port station and opened the system for general users.
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. In
2018, we have introduced a soft X-ray chopper that can transmit only a selected pulse of
the incident beam in order to improve signal to noise ratio of specific experiments liketime-resolved spectroscopy of slow dynamics, operando spectroscopy under applied bias
or to reduce radiation induced damages.
At the beamline endstations, various scientific researches were carried out by both thelaboratory staffs and general users (G-type application). Below are brief introduction ofrecent activities at each station.
(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 addition, an optical parametricamplifier (OPA) has been installed for both laser systems to cover a wider spectrum range
of optical laser.
In 2018, time-resolved photoelectron diffraction experiments were performed on amonatomic two-dimensional layer of Si, Silicene. Two-dimensional detection ofphotoelectron diffraction patterns and a chemical shift in high energy resolution
measurements by ARTOF allow us to trace temporal evolution of Si atom positions in asite-specific manner.
Photo-excited carrier dynamics in a model organic phovoltaic system was studied using
time-resolved soft X-ray photoelectron spectroscopy. Monolayer-thick p-type metal
phthalocyanine (CuPc) and n-type fullerene (C60) layers were deposited on a TiO2(110)
surface. Electrons excited in the unoccupied states of CuPc and C60 are swiftly transferredto the conduction band of TiO2 substrate, leaving the molecules in transient cationic states.
The cationic states have long lifetime of the order of microseconds, suggesting that anelectron-hole recombination is efficiently suppressed at the organic/TiO2 interface.
(2) 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 2018, we have devised new technique enabling to probe the electronics states ofburied interfaces of GaN-HEMT in academia-industry collaboration with Sumitomo
Electric Industries, by combing 3D nano-ESCA with advanced device technologies. This
work was published in Scientific Reports in 2018. As a joint research with Dr. Asakuraand Dr. Hosono at AIST group, we also combined 3D nano-ESCA with optical
microscope images, and studied Li ion diffusion mechanism in a m sized SnO2 wire andlocal Li insertion/extraction process in a Li4Ti5O12 (LTO) negative electrode active
material under operando (electrochemically operating) condition. The result on LTO waspublished in Journal of Electron Spectroscopy and Related Phenomena. As collaboration
with Department of Materials Engineering, the University of Tokyo, we performed
operando nano-spectroscopy on device structures of transition metal dichalcogenide
tunnel field effect transistors (TMD-TFETs) and found difference in gate and drain
voltage dependence of the potential distribution between MoS2 on highly- and low- doped
p+-WSe2. Furthermore, we also conducted academia-industry collaboration research onprocess-induced defects in SiC trench MOSFETs based on the previous results publishedin e-JSSNT in 2018.
(3) Ambient-pressure X-ray photoelectron spectroscopy (AP-XPS)This station allows Operando observation of catalysts under reaction conditions using
AP-XPS. The AP-XPS station was constructed in 2014 by an external funding (JST ACTC project), and was opened to external users in 2018.
The AP-XPS system is equipped with a differentially pumped electron analyzer

(SPECS, PHOIBOS 150 NAP) and an ambient-pressure gas cell. XPS measurements canbe performed both under ultrahigh vacuum and in near-ambient gas pressure up to 20mbar. Catalytic activity is monitored by mass spectrometer, and simultaneous evaluationof adsorbate and catalyst electronic states is performed by AP-XPS. In addition to theexperiments at the free port station using synchrotron soft X-ray, off-line experiments
using a twin-anode X-ray source can be performed.
A variety of research projects are now in progress at 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) CH4
partial oxidation on Pd catalysts, (v) CO2 adsorption on graphene support, (vi) bandalignment at a semiconductor photoelectrode and electrolyte interface, (vii) developmentof time-resolved AP-XPS.
(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 ultrahigh-resolution (E/ΔE > 10,000) and undervarious environmental conditions (gas, liquid, and solid). The number of applications tothe HORNET station is increasing. In 2018, we have performed 15 collaborative researchusing the HORNET station: two S-type proposals, five proposals for molecular systems,
four for condensed matter physics, and four for electrochemistry of batteries. In molecularsystems, the behavior of water in a variety of circumstances was studied, such as wateraround disaccharide, water at the interface of biocompatible polymers, and hydration toplasma treated carbon nanotube and boron nitride. Jet system was installed in order todiscuss pure vibrational spectra without the contribution from an X-ray filter. In
condensed matter physics, characteristic experiments were carried out using theadvantages of RIXS. Charge excitation due to hole doped at oxygen sites inLa2−xSrxNiO4+δ, La2−2xSr1+2xMn3O7, and La1-xSr1+xMnO4 was investigated in comparison
with La2−xSrxCuO4 using elementary selectivity of O K-edge RIXS. Photon-in/photonout process of RIXS enabled to probe electronic structure change due to metal-insulatortransition in Ca2RuO4 induced by electronic field. Angle-resolved RIXS allowed us tomeasure the dispersion of elementary excitation in VO2 and resonant inelastic X-ray
diffraction from La1/3Sr2/3FeO3. In electrochemistry of batteries, we have continuously
studied mechanism of charge/discharge process and explored new electrode materials by
ex-situ and operand RIXS. In order to clarify the effect of charge transfer between metaland oxygen, oxygen-free electrolyte battery cell is being developed. In 2018, several
results for condensed matter physics were published, such as Fe L-edge RIXS of FeS

model complexes and low-spin ferrous and ferric iron complexes, V and Mn L-edge RIXS
of half-metallic ferrimagnet Mn2VAl, Cr L-edge RIXS of ruby, and Co L-edge RIXS ofLaCoO3.

(4) Free-port station
The station is equipped with a focusing mirror chamber, and users can connect their own
experimental chambers. In 2018, the following experiments were performed: time
resolved soft X-ray diffraction of Ba3CuSb2O9; time resolved X-ray absorption
spectroscopy of Eu compounds with valence fluctuations; N K-edge near-edge X-ray
absorption fine structure of 2D organic hetero-bilayer Cat-TTF/Im-SAM on Au;
evaluation of spatial coherence of synchrotron radiation using coherent diffraction
imaging technique; ambient-pressure X-ray photoemission spectroscopy ofH2
adsorption/absorption in Pd alloys and CO2 hydrogenation reactions on Ni-based
catalysts; element-selective analysis of 3D atomic structures of quasi-crystal
BaTiO3(111)/Pt(111) thin film with photoelectron holography technique using Display
type ELlipsoidal Mesh Analyzer (DELMA).