Wide angle-resolved Hard X-ray Photoemission Spectroscopy
BL47XU is an undulator beamline dedicated to promote the utilization of synchrotron
radiation for industry. The light source of this beam line is a standard in-vacuum undulator in
SPring-8 and the X-ray optics adopts a Si (111) direct LN2 cooling double-crystal
monochromator with tunable energy range of 6-35 keV. Two Rh-evaporated mirrors (70 cmlength, reflection direction is horizontal) are placed in the most downstream part of the optics
hutch to eliminate harmonics. The mirrors can be bent for horizontal beam focus. A Si (111)channel-cut monochromator is placed between the monochromator and the mirrors to get finer
energy resolution of incident X-ray for hard X-ray photoemission spectroscopy (HAXPES). The
HAXPES systems at this beam line are equipped with VG-SCIENTA hemispherical R-4000
photoelectron energy analyzers as shown in Fig. 1.

Fig.1 The beam line of BL47U

One of the advantages of HAXPES compared to conventional photoemission spectroscopy isits potential for bulk sensitive measurements in a non-destructive manner. As we know that theprobing depths of PES are determined by the inelastic mean free paths (IMFP) of photoelectrons
within the solid. The conventional PESs (ultraviolet photoemission spectroscopy and X-rayphotoemission) usually utilize radiation from He discharge tube, synchrotron radiation as well
as Al or Mg-anode X-ray tube with energy range of several-ten to several-hundred eV. Theirobtained data are strongly dependent on the surface condition of the sample because detection
depth is shallow due to a short IMFP of photoelectrons inside the solid material. Therefore, ithas been difficult to observe bulk electronic states that contribute to the solid-state properties (asshown in Fig. 2). One of the solutions for this is so-called depth-profiling with sputtering.
However there is a concern about property changes during the sputtering process. The 3rdgeneration synchrotron radiation of SPring-8 with undulator light source enable us to use highbrilliant (photon flux ~1011 photons/sec) hard X-ray (6-8 keV) for high excitation energy
photoemission spectroscopy. The large detection depth of several tens of nanometers (typically,
as around 20 nm for 8 keV) is sufficient for the observation of bulk

electronic states. Besides

standard bulk-sensitive measurements, one can also get deeper core levels as well as asurface-to-bulk profile of electronic states in angle-dependent photoemission spectroscopy
experiments where probing depth can be controlled by changing the detection angle ofphotoelectrons to the sample surface.

Fig. 2 Advantages of HAXPESThe variable depth analysis of electronic properties provided by HAXPES has realized
various applications both in basic and applied research fields. Recently, a wide angle-resolved
hard X-ray photoemission spectroscopy using an objective lens has realized at BL47XU inSPring-8. The objective lens system originally developed to investigate the variable the depth
profile at once without rotating the sample angle along the incidence X-ray. The aim of thiscourse is to learn the principle of HAXPES and gain experience of measuring the core level
photoemission spectra using the objective lens system with angular resolving capability.
Participants will learn how we can realize wide angle-resolved HAXPES to study the depth
analysis of electronic structures in buried interface layers.

On the practices at the BL47XU, we are planning to conduct the followings.
1. Explanation of the beamline optics of BL47XU.
2. Explanation of HAXPES measurement including of the objective lens system.
3. Sample preparation of typical buried layers.
4. Measurement.

5. Data analysis.