Inelastic low-energy electron diffraction

E. Other techniques Low-energy electron diffraction Elastic low-energy electron diffraction Inelastic low-energy electron diffraction Reflection high-energy electron diffraction LEED ELEED ILEED RHEED 50 A Crystalline surface structure Limited applicability 128, 129, 130... 

Many such techniques have been developed and used. Low-Energy Electron Diffraction, in which electrons are elastically scattered off a surface, has been the most successful among those for surface crystallography. Inelastically scattered electrons also... 

Low-Energy Electron Diffraction (LEED) is an electron analog of XRD that can provide the crystal structure over the outer 2-5 nm of a solid s surface. This surface specificity arises from the fact that unlike photons, low-energy electrons (20-200 eV) can only travel a very short distance within a solid before suffering elastic and inelastic collisions whereupon they lose energy. Electrons are directed normal to the surface and the backscattered signal (elastically scattered) is recorded. This displays an XRD-like diffraction pattern. As elecffons are used, HV and clean surfaces are required. 

When a solid is bombarded with high energy electrons the interaction produces secondary electrons (elastic), back-scattered electrons (inelastic), low loss electrons. Auger electrons, photo electrons, electron diffraction, characteristic x-rays, x-ray continuum, light, hole electron pairs and specimen current. These interactions are used to identify the specimen and elements of the specimen and can also be used to physically characterize particulate systems. 

An electron reflected from a surface carries diffraction information if it has experienced elastic scattering or information on the excitation of phonons, plasmons, and electronic or vibrational transitions as the result of inelastic events. The major effort in diffraction studies has concentrated on the use of low energies ( 200 eV) but reflection high-energy electron diffraction (RHEED 20—40keV) is suitable also for surface work (see ref. 2 for a description of pattern interpretation). RHEED... 

Elastic and inelastic colUsions of atoms and molecules at surfaces are also of importance. The scattering of hydrogen and helium from surfaces leads to diffraction patterns in the same manner as with LEED, but since the atoms penetrate the surface far less deeply than even low-energy electrons, the structures obtained reflect the very surface of the sample. The inelastic surface scattering of molecules can be examined in detail using laser and mass spectromet-ric detection for the scattered molecules. Such measurements can be used to model the form of the gas-surface interaction potential, knowledge of which is a prerequisite for any detailed picture of gas-surface reaction dynamics. 

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