region change the properties of the retarding field, therefore influencing the reflected (specular) beam. No LEED pattern is formed, because no scattering events have taken place, and therefore, reflected intensity is high. Low-energy electron holography Low-energy electron holography is realized with electron with kinetic energies in the range 30 - 250 eV. The source of the coherent electron beam is a sharp metal tip and the electrons are extracted by field emission. The wave transmitted through the sample propagates to the detector where the interference pattern is acquired, formed by superposition of the scattered with the non-scattered (reference) wave, constituting an in-line hologram. The structure of the object (macromolecule) is then reconstructed from the hologram by numerical methods. Low-energy electron holography has successfully been applied for imaging of individual biological molecules, including: purple protein membrane, DNA molecules, phthalocyaninato polysiloxane molecules, the tobacco mosaic virus8, a bacteriophage, ferritin and individual proteins (bovine serum albumin, cytochrome C and hemoglobin). The resolution achieved by low-energy electron holography is about 0.7 - 1 nm. Reflectivity contrast imaging The elastic backscattering of low energy electrons from surfaces is strong. The reflectivity coefficients of surfaces depend strongly on the energy of incident electrons and the nuclear charge, in a non-monotonic fashion. Therefore, contrast can be maximized by varying the energy of the electrons incident at the surface. Spin-polarized LEEM (SPLEEM) SPLEEM uses spin-polarized illumination electrons to image the magnetic structure of a surface by way of spin-spin coupling of the incident electrons with that of the surface. Other Other advanced techniques include: Low-Energy Electron Potentiometry: Determining the shift of LEEM spectra allows the determination of local work function and electrical potential. ARRES: Angular Resolved Reflected Electron Spectroscopy. eV-TEM: Transmission Electron Microscopy at LEEM energies. References Electron microscopy techniques Scientific techniques