Geometry grazing incidence

FIGURE 27.7 Grazing incidence X-ray scattering geometry. The X-rays are incident on the sample at an angle (j) and are detected at a combination of two angles 29 and 2c ). ... 

Very thin films exhibit special structure because of their confined geometry between substrate and surface. Their structure cannot be studied in a normal setup. In order to obtain enough photons on the detector, the X-ray beam must impinge on them under grazing incidence (Cf. Sects. 7.6.3.1,1.63.2, 8.8). This technique is suitably combined with microbeams. Current effort is focusing both on progress of the instrumentation and on the development of adapted analysis methods. 

Ruland and Smarsly [9,84,240] can analyze their recorded data in the classical Born approximation, but have to correct for the special geometry of the grazing incidence experiment. They propose not to carry out the necessary corrections in a... 

Figure 3.2 The effect of glancing incidence geometry, calculated for a 150 nm lno.5i77Gao. 4823As film on a (001) InP substrate. The symmetric 004 and the grazing incidence 044 curves are shown...

Figure 3.7 (a) Grazing incidence geometry, (b) Grazing exit geometry, (c) Symmetric scan. (Coustesy K.M.Matney)... 

Figure 6.4 Schematics of the relationship between X-ray characterization and the crystal state of the thin films, (a)-(c), and the scattering geometry of the grazing incidence X-ray diffraction in the reciprocal space, (d).

XRD requires a periodic two- or three-dimensional structure at the surface of a specimen. The measurements are performed in a similar electrochemical cell as described for XAS. The removal of the electrolyte due to the pressing of the polymer window on the specimen surface reduces the disturbing X-ray scattering from water. The grazing incidence geometry weakens the contribution of the diffraction of the... 

According to [18,19] and our experience, it is usual that the smaller FWHM for symmetrical reflections (measuring mostly tilt mosaicity) corresponds to a larger FWHM for asymmetrical reflections (measuring together twist and tilt mosaicity). For example, for the MOCVD GaN layer which possessed a 00.2 RC of only 40 arc sec, the 10.2 reflection exhibited an FWHM of 740 arc sec [18], Similarly, for a 0.76 pm MBE layer, Amano et al [19] reported 48 arc sec for the 00.2 reflection and 5226 arc sec for the 10.0 reflection (grazing incidence geometry). The other sample (1.7 pm) possessed 365 arc sec and 1581 arc sec, respectively, for those two reflections. 

Grazing incidence Optical microscopy Small-angle scattering Surface scattering Synchrotron radiation Thin film geometry... 

---