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VUV

Beamline VUV-Photoemission

Paolo Moras  -

Laboratory: Elettra

Trieste
 
The VUV-Photoemission beamline at the synchrotron Elettra (Trieste) is dedicated to the study of the electronic and magnetic structure of solid systems by photoemission spectroscopy. The valence band, Fermi surface and core levels of these systems, which define their chemical, electronic, optical and transport properties, can be analyzed in detail owing to the unique combination of high brilliance and tunability of the synchrotron light and the high energy and angle resolution provided by the Scienta R4000 electron spectrometer. Samples can be studied over a wide range of temperatures and using different scanning geometries, thanks to the 5-degree of freedom cryo-manipulator. The data acquisition setup is automatized and employs user-friendly software. The preparation and structural characterization of the samples can be performed in-situ under ultra-high vacuum conditions by sputtering, annealing, cooling, epitaxial deposition of various materials, exposure to gases, and low-energy electron diffraction.

Further information at: http://www.elettra.eu/elettra-beamlines/vuv.html

 

TECHNICAL SPECIFICATIONS

Beamline

  • Photon energy: 20-750 eV.
  • Resolving power: 20000 at 65 eV, 14000 at 400 eV.
  • Light polarization: horizontal.
  • Measurement chamber
  • Base pressure: 5 × 10-11  mbar.
  • Sample temperature: 9 - 450 K.
  • Degrees of freedom of the manipulator: 5.
  • Energy and angle resolution of the electron spectrometer: 2 meV (at 5 eV pass energy) and 0.1°.

Preparation chamber

  • Base pressure: 1 × 10-10 mbar (up to 10-6 mbar during controlled exposure to pure gases)  mbar.
  • Sample temperature: 77 - 1000 K (liquid nitrogen cooling and electron beam annealing).
  • Degrees of freedom of the manipulator: 5.

Heating chamber

  • Base pressure: 5 × 10-9 mbar -10 mbar (up to 10-3 mbar during controlled exposure to pure gases).
  • Sample temperature: 300 - 2000 K (electron beam annealing).
  • Sample parking stage
  • Magnetization coil

AVAILABLE TECHNIQUES

Measurement chamber

  • Angle-resolved photoemission spectroscopy (ARPES) for valence band and Fermi surface mapping.
  • High-resolution X-ray photoemission spectroscopy of core levels (XPS).
  • X-ray photoelectron diffraction (XPD).
  • X-ray absorption spectroscopy (XAS).
  • Residual gas analysis (RGA).

Preparation chamber

  • Low-energy electron diffraction (LEED).
  • Molecular beam epitaxy (MBE) controlled by a quartz micro-balance.
  • Ion sputtering.
  • Residual gas analysis (RGA).

Heating chamber

  • Chemical vapor deposition (CVD).
 

SAMPLES

  • The electrical conductivity of the samples must be high enough to avoid charging effects.

  • Metals, small gap semiconductors and ultra-thin insulating films are usually suitable materials for the analysis by photoemission spectroscopy.

  • Lateral size: from 2 × 2 to 10 × 10 mm22.

  • Thickness: up to 2 mm.

USED FOR

Study of the electronic and magnetic structure of:

  • 2D materials (e.g. graphene, silicene, antimonene);

  • topological matter (topological insulators, Weyl semi-metals);

  • low-dimensional systems with high spin-orbit coupling and/or magnetic interactions;

  • self-assembled molecular layers.

 
 

Case Studies

Indirect chiral magnetic exchange through Dzyaloshinskii–Moriya-enhanced RKKY interactions in manganese oxide chains on Ir(100)

Manganese oxide chains grown on Ir(100) display a non-collinear spiral magnetic structure, which has been identified by spin-polarized scanning tunneling microscopy and theory. ARPES spectra show the effects on the Mn 3d states of the anti-ferromagnetic ordering along the chains, where the Mn atoms are adjacent.

See: M. Schmitt et al., Nat. Commun. 10, 2610 (2019)

 
 
 

Electronic States of Silicene Allotropes on Ag(111)

Silicene is a honeycomb-like material similar to graphene and consisting of a single layer of silicon atoms. Some silicene allotropes can be synthesized on Ag(111). The ARPES analysis shows that these allotropic forms present σ-derived bands, while the π-derived bands expected in the proximity of the Fermi level are fully de-localized in Ag the substrate. This hybridization does not allow the formation of Dirac cones, at variance with the case of free-standing silicene.

See: P.M. Sheverdyaeva et al., ACS Nano 11, 975 (2017).

 
 
 
 
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