Low energy electron microscopy (LEEM) is a new technique for surface imaging, based on the wave nature of the electron. Although it makes use of electron lenses as in conventional electron microscopes it differs from them in that the electrons have energies of the order 1-100 eV when they interact with the surface. As a consequence, the method is very surface-sensitive and the probing depth may be tuned by varying the energy. Contrast is mainly produced by diffraction. Resolution is determined mainly by the chromatic and spherical aberration of the decelerating/accelerating field in front of the specimen. LEEM is easily combined with low energy electron diffraction (LEED), photoemission electron microscopy (PEEM) and other emission microscopies. The specimen is easily accessible which allows a wide variety of in situ studies over a wide temperature range.The review gives an introduction to the basic electron-specimen interaction processes, to the instrumentation and to the factors which govern contrast and resolution. The remaining, larger part of the review deals with applications to clean surfaces, atom-surface interactions and thin films. Topics discussed include topography, phase transitions, adsorption, reaction, segregation, growth, sublimation and magnetic microstructure. Related techniques are also discussed briefly.

No abstract

No abstract

The instrumentation for synchrotron radiation X-ray photoemission electron microscopy (XPEEM) has recently undergone significant improvements, finding application in diverse fields such as magnetism, chemistry, surface science and nanostructure characterization. The spectroscopic photoemission and low energy electron microscope (SPELEEM) operational at the 'Nanospectroscopy beamline' at the Elettra synchrotron facility combines structural and spectroscopic analysis methods in a single instrument, exploiting the inherent chemical sensitivity of X rays. The SPELEEM reaches an energy resolution of 0.2 eV and a lateral resolution of few tens of nanometers in XPEEM. Selected results are used to illustrate the spectro-microscopic capabilities of the SPELEEM, and the usefulness of available complementary methods such as low energy electron microscopy (LEEM) and micro-spot low energy electron diffraction (LEED).

The nanoscale spin structure of head-to-head domain walls in mesoscopic ferromagnetic rings has been studied by high-resolution nonintrusive photoemission electron microscopy as a function of both ring width (100-730 nm) and film thickness (2-38 nm). Depending on the geometry, two types of head-to-head domain walls are found (vortex and transverse walls). The experimental phase diagram, which identifies the transition between the wall types, is compared to analytical calculations of the energy and micromagnetic simulations, which are found to agree well with the experimental results.