Short range order in amorphous

Golan Y, Ter-Ovanesyan E, Manassen Y, Margulis L, Hodes G, Rubinstein I, BitheU EG, Hutchison JL (1996) Electrodeposited quantum dots IV. Epitaxial short-range order in amorphous semiconductor nanostructures. Surf Sci 350 277-284... 

In an analysis of an electron-diffraction study of short-range order in amorphous films of NisGes, the relative arrangement of the atoms in the films has been shown to differ from the co-ordination that is characteristic of the inter-metallic compound. 

The Description of the Short-range Order in Amorphous Semiconductors... 

Therefore the only way towards describing the three-dimensional short-range order in amorphous semiconductors is the construction of structural models. 

It is mth this in mind that in the present chapter (2.5) only the nearest neighbour configuration will be used to classify these materials (Table 2.1). A more detailed treatment of the short-range order in amorphous semiconductors including, at least in principle, the whole more or less ordered region around an arbitrary atom is given in the next chapter (2.6). 

For the time being the situation is still fluid. New ideas are pouring in, others are eUminated. A convenient formaUsm of describing statistically the three-dimensional short-range order in amorphous semiconductors seems to emerge from the continuous network approach and will be highly appreciated by both the experimentalist and the theoretician. 

Structural microheterogeneity due to the changes in the mutual disposition of macromolecules in relation to each other in the surface and transition layers at different distances from the phase boundary and characterizing the short-range order in amorphous polymers and degree of crystallinity in crystalline polymers... 

The short-range order in a material is important in determining optoelectronic properties. For instance, x-ray and electron diffraction experiments performed on amorphous siHcon (i -Si) and germanium (a-Ge) have revealed that the nearest neighbor environments are approximately the same as those found in their crystalline counterparts (6) photoemission experiments performed on i -Si show that the DOS in valence and conduction bands are virtually identical to the corresponding crystal with the exception that the singularities (associated with periodicity) present in the latter are smeared out in the former. 

Packing efficiency can also be described by the extent of short-range order in the amorphous state. Mitchell has shown through X-ray scattering studies that, while the local molecular organization of noncrystalline polymers is random, in many cases, there are additional correlations that do not perturb the chain trajectory but will impact polymer properties.15 These correlations have a limited spatial range (<50A) but will have a particular impact on bulk properties... 

The optical properties of amorphous solids are interesting. These solids are optically isotropic. Furthermore, the sharp features present in crystal spectra are absent in the spectra of amorphous solids even at low temperatures. The overall features in the electronic spectra of amorphous solids (broad band maxima) are, however, not unlike those of crystals, reflecting the importance of short-range order in determining these characteristics. The optical absorption edges of amorphous materials are not sharp and there is an exponential tail in the absorption coefficient (Fig. 7.13) associated with the intrinsic disorder. 

The degree of short-range order in an amorphous material can be characterized by a hard sphere model if the basic structure of an amorphous material is approximated by spheres. The density of packing of atoms around a reference atom is described by the number of atom centers per volume that lie in a spherical shell of thickness, dr, and radius about the reference atom. In a hard sphere model, the number, n, of neighboring spheres with centers between r and dr is measured as a function of r. 

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