Broadening dislocation

Hagen, W.R. 1981. Dislocation strain broadening as a source of anisotropic linewidth and asymmetrical lineshape in the electron paramagnetic resonance spectrum of metal-loproteins and related systems. Journal of Magnetic Resonance 44 447-469. 

Figure 6.1 Double-axis rocking curve of CdTe on GaAs showing the broadening due to the very high dislocation density in the layer. (Courtesy R.l.Port, Durham University.) The rocking curve width in such thick, high mismatched layers falls with increasing layer...

In Equation 4.1, the factor fiF(0) is included, which is the peak profile function, that describes particle size broadening and other sources of peak broadening. The XRD method can be used as well for the measurement of the crystallite size of powders by applying the Scherrer-Williamson-Hall methodology [4,35], In this methodology, the FWHM of a diffraction peak, p, is affected by two types of defects, that is, the dislocations, which are related to the stress of the sample, and the grain size. It is possible to write [35]... 

The rocking curve is broadened by various factors. To extract them it is necessary to apply triple axis diffractometry, an extension of RC analysis. The recent work of Metzger et al [41] shows how it is possible, using this technique, to estimate correlation lengths of columnar crystallites, dislocation densities and angles of rotational disorder. 

As shown schematically in Figure 13.4c, the strain can change among different crystallites, e.g. as a consequence of plastic deformation in an elastically anisotropic medium, but can also vary across each crystallite, e.g. because of the presence of dislocations (the two terms are sometimes referred to as strain of the second and third kind, respectively). Notably, a strain broadening effect can be observed even if the macrostrain (mean value of the strain distribution) is zero (Figure 13.4c), as in a powder sample. Otherwise, the simultaneous effect of macrostrain and microstrain results in a shift and broadening of the diffraction profile (Figure 13.4d). 

Generalized line defects, like dislocations and disclinations, are known to produce a markedly anisotropic line broadening, i.e. a line broadening dependent on the observed [hkl direction in the crystalline domain. This is due to the combined effect of the anisotropy of the elastic medium (described by the... 

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