The Ultra Resolved ANgular phOtoelectron Spectroscopy beamline (URANOS) is an experimental installation for studies of the electronic structure of solid surfaces by Angle-Resolved PhotoElectron Spectroscopy (ARPES) technique in the range from 8 to 170 eV with any selectable polarization. The beamline is designed for high photon flux, high resolution, variable polarization, and minimal harmonic contamination.
The ARPES technique has an extremely important place among methods of studying the structure of matter because it allows the measurement of fundamental parameters for electrons: energy, momentum and spin. Direct measurement of these parameters is performed for photoelectrons in a vacuum above the surface of the sample. Within the so-called sudden approximation, these parameters can be related to the binding energy and momentum of the electron in the sample prior to the photoelectric excitation.
Due to this technique, it is possible to study the band structure quickly and thoroughly in four dimensions (kx, ky, kz, and E) including the effects of electron correlations, electron-phonon, electron-dopant interactions. In other words, this technique provides a direct measurement of the multidimensional dispersion relation E(k) in solids.
In addition, the URANOS beamline enables X-ray Photoelectron Spectroscopy (XPS) measurements up to 500 eV, X-ray photoelectron spectroscopy techniques with extreme surface and angular sensitivity (SXPS, SX-ARPES, GI/TR-XPS) and studies of the crystallographic structure of the surface by low energy electron diffraction (LEED) are also possible.
Expansion of the system by modules enabling spin-resolved (Spin-ARPES) measurements (3D VLEED spin filters) is planned for 2023.
- ARPES (Angle-resolved photoelectron spectroscopy),
- Spin-ARPES (installation of spin filters scheduled for 2023),
- CD-ARPES (Circular Dichroism ARPES),
- RES-ARPES (RESonant ARPES),
- XPS (X-ray Photoelectron Spectroscopy),
- S-XPS (Soft X-ray Photoelectron Spectroscopy),
- GI/TR-XPS (Grazing Incidence/Total Reflection XPS),
- Low energy electron diffraction (LEED) with minimal exposure (MCP detector).
Figure 1. ARPES measurement scheme.
The most important features of the URANOS beamline are as follows:
- automatic measurements of the multidimensional dispersion relation E(k) with ultra-high energy and angular resolution and at very low temperatures (<10K),
- spectrally pure (contamination of higher harmonics <1%), monochromatic photon beam with a wide range of energy and any polarization,
- extensive possibilities of in situ sample preparation.
Figure 2. Band structure of a NbP Weyl semimetal measured at an excitation energy of 92 eV with visible Fermi arcs. Link.
|Source||Elliptically polarizing undulator (EPU) type APPLE II, quasi-periodic. Magnetic structure period: 120mm.|
|Available energy range||Total: 8–500 eV
NIM: 8 eV–30 eV
PGM: 14 eV–500 eV
|Energy resolution ΔE/E||5x10-5|
|Beam size at the sample (H x V)||60 μm x 150 μm / 60 μm x 60 μm (with a limited photon flux)|
|Photon flux at sample||>5 x 1011 fotons/s @ 20 000 RP|
|Polarization||Any, selectable: Linear Horizontal, Linear Vertical, Circular Left, Circular Right, Ellipticals, Linear Skews|
|End station||(High resolution) angle-resolved photoelectron spectroscopy - (HR)-ARPES,
(angle-resolution) photoelectron spectroscopy in the soft X-ray range - SX-(AR)PES
X-ray photoelectron spectroscopy in TR-XPS total reflection regime
Low energy electron diffraction (LEED) with minimal exposure (MCP detector)
|ARPES end station||DA30L with deflectors (3D VLEED from 2024)|
|Detector resolution||1.8 meV, 0.1°|
|Temperature range||6.5 – 500 K @ 5 - axis|
|Diffractometer||OCI LEED 800 MCP I(V)|
|Samples storage||12 / 24|
|Preparation chamber||Mini-LEED, RGA, QMB, IBA, AMD|
|Preparation temperature||150 – 2000 K (RES, EB – direct heating)|
|Installation of user devices||3 ports for connecting user devices and 1 port for the vacuum case|