High energy electron diffraction

HEED High-energy electron diffraction [104] Diffraction of elastically back-scattered electrons (-20 keV, grazing incidence) Surface structure... 

RHEED Reflection high-energy electron diffraction [78, 106] Similar to HEED Surface structure, composition... 

SHEED Scanning high-energy electron diffraction [106] Scanning version of HEED Surface heterogeneity... 

Ichimiya A, Ohno Y and Horio Y 1997 Structural analysis of crystal surfaces by reflection high energy electron diffraction Surf. Rev. Left 4 501-11... 

HEED = high energy electron diffraction IILE = ion-induced light emission INS = ion-neutralization spectroscopy IRS = infrared spectroscopy ISS = ion-scattering spectroscopy LEED = low energy electron diffraction LEIS = low energy ion scattering ... 

Fig. 4. Schematic of an ultrahigh vacuum molecular beam epitaxy (MBE) growth chamber, showing the source ovens from which the Group 111—V elements are evaporated the shutters corresponding to the required elements, such as that ia front of Source 1, which control the composition of the grown layer an electron gun which produces a beam for reflection high energy electron diffraction (rheed) and monitors the crystal stmcture of the growing layer and the substrate holder which rotates to provide more uniformity ia the deposited film. After Ref. 14, see text.

Reflection High-Energy Electron Diffraction (RHEED)... 

This chapter contains articles on six techniques that provide structural information on surfaces, interfeces, and thin films. They use X rays (X-ray diffraction, XRD, and Extended X-ray Absorption Fine-Structure, EXAFS), electrons (Low-Energy Electron Diffraction, LEED, and Reflection High-Energy Electron Diffraction, RHEED), or X rays in and electrons out (Surfece Extended X-ray Absorption Fine Structure, SEXAFS, and X-ray Photoelectron Diffraction, XPD). In their usual form, XRD and EXAFS are bulk methods, since X rays probe many microns deep, whereas the other techniques are surfece sensitive. There are, however, ways to make XRD and EXAFS much more surfece sensitive. For EXAFS this converts the technique into SEXAFS, which can have submonolayer sensitivity. 

Alternatives to XRD include transmission electron microscopy (TEM) and diffraction, Low-Energy and Reflection High-Energy Electron Diffraction (LEED and RHEED), extended X-ray Absorption Fine Structure (EXAFS), and neutron diffraction. LEED and RHEED are limited to surfaces and do not probe the bulk of thin films. The elemental sensitivity in neutron diffraction is quite different from XRD, but neutron sources are much weaker than X-ray sources. Neutrons are, however, sensitive to magnetic moments. If adequately large specimens are available, neutron diffraction is a good alternative for low-Z materials and for materials where the magnetic structure is of interest. 

M. G. Lagally. In Reflection High-Energy Electron Diffraction andRflection Electron Imaging ofSutfzces. (P. K. Larsen and P. J. Dobson, Eds.) Plenum, New York, 1989. 

Reflected High Energy Electron Diffraction Scanning Reflection Electron Microscopy... 

RHEED Reflection high-energy electron diffraction... 

When high-energy electrons are injected into thin specimen, most of them tend to pass through without any perturbation occurring from the substances, because the cross section of atomic nuclei is small enough to such electrons. Some of the incident electrons are elastically scattered to be diffracted, and the others... 

In the process of MBE, the surface structure can be investigated by reflected high energy electron diffraction (RHEED). During MBE growth, one often observes an oscillation in the intensity of the specular reflected beam as a function of time. This is interpreted to be due to the layer-by-layer growth of a two-dimensional island. 

S. Clake, D. D. Vvedensky. Origin of reflection high-energy electron-diffraction intensity oscillations during molecular-beam epitaxy a computational modeling approach. Phys Rev Lett 55 2235, 1987. 

Surface morphology Reflection high-energy electron diffraction (RHEED) Atomic force microscopy (AFM)... 

When a high-energy electron beam in an electron microscope hits a sample, a wealth of information becomes available through a number of scattering, diffraction and decay processes (Fig. 4.13). Indicate how these may be used to obtain additional information about the sample. 

Fig. 4.1 Reflection high-energy electron diffraction (RHEED) patterns corresponding to the best epitaxial conditions of CdSe deposited on a (111) InP face (thickness 85 nm). (a) Observation under the (112) azimuth (b) observation under the (110) azimuth. (With kind permission from Springer Science-l-Business Media [6])...

Kinetic equation, optical potential, tensor theory and structure factor refinement in high-energy electron diffraction... 

In summary, the movement of a high-energy electron in a solid may be described by a set of three Equations (1), (4) and (6). From these equations we may conclude that for high-energy electron diffraction the problem of multiple elastic and inelastic scattering by a solid is entirely determined by two functions, i.e. (1) the Coulomb interaction potential averaged over the motion of the crystal particles (V(r)> and (2) the mixed dynamic form factor S(r, r, E) of inelastic excitations of the solid. 

In this section we will discuss perturbation methods suitable for high-energy electron diffraction. For simplicity, in this section we will be concerned with only periodic structures and a transmission diffraction geometry. In the context of electron diffraction theory, the perturbation method has been extensively used and developed. Applications have been made to take into account the effects of weak beams [44, 45] inelastic scattering [46] higher-order Laue zone diffraction [47] crystal structure determination [48] and crystal structure factors refinement [38, 49]. A formal mathematical expression for the first order partial derivatives of the scattering matrix has been derived by Speer et al. [50], and a formal second order perturbation theory has been developed by Peng [22,34],... 

Bird, D.M. and King, Q.A. (1990) Absorptive form factor for high-energy electron diffraction, Acta Cryst. A, 46, 202-208. 

Peng, L.-M., and Dudarev, S.L. (1993) Tensor theories of high energy electron diffraction and their use in surface crystallography, Surface Sci., 298, 316-330. 

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