The first tests of new equipment have been performed at the end of the September 2007. Both analyzers and the new sample scanning stage demonstrated reasonable performance that will be enhanced during this shutdown period. On the figure below the image acquired using the new analyzer is shown.
Scanning photoemission image of Au coated mesh. The mesh period is 63.3 micron, photon energy 95 eV, kinetic energy 85 eV
Overview
The SM beamline is right now under an intensive upgrade. After the upgrade it will be an unique instrument to study the band structure and the Fermi surface topography. A low photon energy beam (below 100eV) is focused into a submicron spot and electrons arising from the photoemission process will be collected in Angular-resolved mode (ARPES).
Moreover with a number of other improvements the general beamline performance will be enhanced.
The beamline is dedicated for the angular resolved valence band photoemission microscopy. The photon energy range available after the monochromator (20-300 eV) is reduced due to the final focalization obtained with a Schwarzschild objective configuration. The beamline will be equipped with two Schwarzschild objectives. The mirrors of both objectives has a multilayer coating, which maximize the normal incidence reflection at the given photon energy. The photon energies will be 27 eV and 95 eV. ARPES will then be performed at these two photon energies. A controlled temperature range (40-400 K) is available too.
The SpectroMicroscopy beamline comprises the monochromator and the microscope joined at the pinhole "P". The source is the U12.5 undulator mounted at the 3.2 section of ELETTRA and shared with the VUV Photoemission beamline. The beamline is based on a variable angle spherical grating monochromator with two gratings optimized for two photon energies engaged. Besides the monochromatisation action, the beamline performs a predemagnification of the X-rays by forming a focused image of the source at a pinhole "P" placed at the beginning of the microscope section of the beamline (size = 6 µm H × 4 µm V).
Technical data
X-rays at sample
After upgrade, two photon energies will be available at the sample.
Energy, eV
Flux, ph/s
Spot Ø, nm
27
8.5×1011
100
95
5.5×1012
500
Microscope
For the detection of electron photoemission, there are two electron analyzers. One is working in the angular-resolved mode, the second in the angular-integrated mode.
Angle-resolved analyzer
Two angular θ-φ rotations
2D detector: E,θ dispersion
Angular resolution 0.3 deg
Acceptance angle 8 deg
Mean radius: 40 mm
Energy resolution: 15 meV, at PE=2 eV
Working distance: 15 mm
Entrance slit: 1 x 4 mm2
Angle-integrated analyzer
Mean radius: 150 mm
Energy resolution: 70 meV
Working distance: 60 mm
16-channel detector
Samples must be conductive. Samples can be heated up during measurements to 400 K and cooled down to 40 K using liquid helium. Any other treatment of the sample surface will be performed in UHV in a separate chamber connected with the microscope one.
