Soft X-ray Photoelectron and Absorption Spectroscopy

PHELIX beamline (where “PH” corresponds to photoelectrons, “HELI” indicates the possibility of light polarization change and “X” defines the energy of radiation which is within the X-ray range) at SOLARIS synchrotron covers a soft X-ray energy range of radiation. It is designed to perform many kinds of complementary spectroscopic measurements under ultra-high vacuum conditions not only ex situ but also in situ, offering variety of preparation possibilities. All beamline and end-station components were customized and built from the ground up for those particular purposes. The source of the radiation is the elliptically polarizing undulator (EPU) giving variable polarization and exceptionally bright light in comparison to conventional X-ray sources. The available photon energy range is 50-1500 eV which is suitable for research on vast majority of materials. The end-station provides not only the opportunity to measure resonant photoemission, circular-dichroic spectra or X-ray absorption spectra with total fluorescence and total electron yield modes but, most of all, to map band structures in three dimensional k-space with angle-resolved photoelectron spectra and to obtain direct 3D spin texture information. The possibility to conduct circular dichroic and spin resolved measurements for the same sample in the same UHV system has a lot of advantages for better understanding of investigated systems excluding the influence of different surface quality and its impact on the outcome. Up to our knowledge, PHELIX beamline is one of only a few places where such combined measurements can be performed.

The UHV end-station gives the possibility to prepare samples in situ and allows to many post-preparation operations on sample. It includes a main preparation chamber, an additional preparation chamber, an UHV cleaver, a sample storage and a load-lock chamber. For samples mounting flag style holders are used, but for distribution purposes within the UHV system a PTS (PREVAC) adapter is needed.

The main preparation chamber is equipped with:
• 4-axes manipulator adapted for cooling with liquid nitrogen and maintaining stable higher temperature to 1300 K with the ability to temporarily elevate the temperature to 2500 K
• two electron beam evaporators and two effusion cells in the chamber with the room to install more as well as leak valves for gas dosing
• linear shift along the main axis of the chamber, it is motorized and, together with a thickness monitor and a mask between a sample and evaporators with rectangular aperture, it enables to deposit wedge samples or samples with different layers on one substrate
• LEED-AES spectrometer with high image resolution and an integrated miniature electron gun
• a residual gas analyzer (RGA) with a quadrupole filter and particles mass detection to 100 amu
• an ion gun for surface cleaning by sputtering with Ar+

The additional preparation chamber:
• equipped with a 4-axes manipulator with a module for liquid nitrogen cooling
• intended for sustaining relatively high pressure up to 800 mbar for reaction of samples with different gases
• the reactions may occur in elevated temperature up to 1300 K.

Contact: Tomasz Sobol
phone: +48 12 664 41 46; +48 12 664 4122 (Beamline)


Measurements parameters:

Radiation Source:
elliptically polarizing undulator (EPU), APPLE II type with permanent magnets

Photon energy range:
50–1500 eV for horizontal polarization
50–1500 eV for circular polarization
50–1500 eV for vertical polarization
70–1500 eV for linear polarization inclined at 45°

Maximum resolving power (RP):
> 10 000

The maximum size of the excited area on the sample:
100 µm x 100 µm with the resolving power (RP) ≥ 10 000 over the entire energy range and for all polarizations

Photon flux on the sample:
≥ 1×1013 photons/s/0.1% B.W. for 50 eV and ≥ 1×1011 photons/s/0.1% B.W. for 1500 eV, for maximum RP and electron current in the storage ring (500 mA)

Measurement equipment:
Hemispherical energy analyzer PHOIBOS 225
3D VLEED FERRUM spin detector with SPECS spin rotator
Photodiode AXUV100
Contacts for drain current measurements
He UV source with monochromator
Standard X-ray source

Available techniques:
Photoelectron Spectroscopy – PES (ResPES, SX-ARPES, SR-ARPES, CD-ARPES, XPS, UPS)
X-ray Absorption Spectrsocopy – XAS (TFY, TEY)

Measurement temperatures:
LHe station 10 – 400 K, Res station: RT – 1100 K

Detailed information can be found on the beamline’s main homepage.