In electron spectroscopy for chemical analysis (ESCA) microscopy, the X-ray emitted photo electrons are detected and analyzed in terms of their kinetic energy. Small shifts in element specific core or valence energies signalize changes and can give detailed information about bond bindings. ESCA is a method sensitive to the chemical information of few monolayers and offers therefore a special instrument for surface sensitive chemical analysis of heterogeneous materials.
The ESCA microscopy beamline at ELETTRA houses a worldwide unique instrument allowing combining chemically surface sensitive measurements with high spatial resolution. A beam spot down to 200 nm and energy sensitivity within 160 meV using a third generation X-ray source providing more than 109 photons/s in the probe has opened the opportunity for material science to perform micro-characterization on a spatial scale comparable to that of the processes and the phases occurring on morphologically and chemically complex surfaces, such as catalysts, electronic and magnetic devices, etc.
With respect to the other photoelectron microscopy techniques a Scanning PhotoEmission Microscope (SPEM) uses the most direct approach to photoelectron spectromicroscopy which is the use of a small focused photon probe to illuminate the surface. The SPEM at the Elettra synchrotron light source can operate in two modes: imaging and spectroscopy. In the first mode the sample surface is mapped by synchronized-scanning the sample with respect to the focused photon beam and collecting photoelectrons with a selected kinetic energy. The second mode is photoelectron spectroscopy from a microspot.
The microscope at the ESCA microscopy beamline is used exclusively for x-ray photoelectron (XPS) microscopy. The experimental apparatus allows to carry out a manifold of experiments, aiming at quantitative and qualitative chemical characterisation of morphologically complex natural and fabricated materials (electronic devices, superconductors, catalysts, thin films, materials with corrosion damage, etc ), including chemical reactions and mass transport processes leading to lateral changes in the composition, morphology and electronic properties of materials.
Research and recent publications
Thermal growth and structural and optical characterization of indium tin
oxide nanopyramids, nanoislands, and tubes;
D. Maestre, A. Cremades, J. Piqueras, and L. Gregoratti;
JOURNAL OF APPLIED PHYSICS 103, 093531 (2008)
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Samples must be conductive. Insulators are hardly imaged due to charging. Samples can be heated up during measurements to 1100 K by e-beam bombardment, filaments, Al2O3, BN heaters, and cooled down to 150 K using liquid nitrogen. The maximum pressure allowed during microscopy experiments is 6·10-7 mbar.
