BL PracticeBL27SU : Soft X-ray Photoemission and Photoabsorption Spectroscopy
1.

Introduction
In this course, the participants will practice experimental methods of soft x-ray

photoemission and photoabsorption spectroscopy.
Photoemission spectroscopy (PES) is a powerful technique for studying electronicstates in solids. Using soft x-rays with photon energies ∼ 1keV for the excitation light
has the advantage of increased bulk sensitivity compared to the use of low energy light(≤ 100 eV). The high energy resolution and high flux obtained at SPring-8 by combining
the high-brilliance synchrotron light source with a high-resolution soft x-ray
monochromator make it possible to observe electronic structures with unprecedented
detail. During the course we will record photoemission spectra at the high-resolution
soft x-ray beamline BL27SU.
Soft x-ray absorption spectroscopy is also useful for studying the electronic states ofwide range materials since the soft x-ray energy range includes the absorption edges ofthe light elements as well as the transition metals and rare earth elements. For the soft
x-ray absorption spectroscopy of metallic materials, the total electron yield method isconventionally used, where the drain current of a sample is measured. This method is,
however, not applicable to insulators. In this course, we will try to obtain
photoabsorption spectra by means of the total fluorescence yield method, which can beapplied to insulators.
2.

Experiments
2.1. Photoemission spectroscopyFirstly, the participants will mount a sample onto a sample carrier which is a copper

plate sample carrier, which has with a size of about 2 × 2 cm. A NiO single crystal will be
used for the sample. The sample carrier will be installed into the airlock of the ultrahighvacuum system. After evacuating the airlock, the sample carrier will be transferred tothe measurement chamber with a transfer rod, and attached to the sample manipulator.
For PES measurements, a clean sample surface is required. This will be obtained bycleaving the sample in the ultrahigh vacuum chamber. A hemispherical-type
photoelectron analyzer will be used for the PES measurements. Before themeasurements, we have to set the parameters of the beamline such as the undulator
gap, photon energy, and resolving power of the monochromator. This can easily be doneusing the system control software in place at the beamline. After setting the beamline

parameters, the sample position will be adjusted using a motor-controlled sample
manipulator to the position of maximum photoemission intensity. Then we will record
some valence band and core level photoemission spectra.
2.2. Photoabsorption spectroscopy
The fluorescence yield detector is also mounted on the same chamber used for thePES measurements, so we can measure photoabsorption spectra for the same sample
without breaking the vacuum. A micro-channel plate detector (MCP) is used for thefluorescence yield detection, which is carried out by the pulse counting of MCP signals.
The sample position will be re-adjusted for maximum count rate. Photoabsorption
spectra are measured by simultaneously scanning both the monochromator postition
and the undulator gap. The drain current of a post-focusing mirror is also monitored toallow normalization to the incident photon flux. We will record the Ni 2p and O 1sabsorption spectra of NiO.

The experimental setup, viewed from above.
Photoelectron analyzer
SPECS: PHOIBOS 150

Transferrod

Preparationchamber

AirlockSRThe fluorescence yielddetector is mounted here.

Vacuumpumps

Slit-lesssoft x-ray emission
spectrometerNot usedin this practice course.