$silicon x ray diffraction pattern$

As well as the fact that the intensity of the rather sharp peak may vary over orders of magnitude down to the background level, sometimes there are broad shoulders or even subpeaks visible on both sides. As a result of this, the appearance of the 200 peak differs significantly from measurement to measurement. Since the in-plane orientation of a sample for specular ω–2Θ measurements is usually not of interest, nobody cares in this sense about obtaining an exact and repeatable sample orientation. Nevertheless, it seems to be worth discussing the behaviour of the Si 200 reflection for a conventional diffractometer in more detail. 2011 ▶) and nanostructures (Kozlowski et al., 2012 ▶), and the atomic ordering in Ge/Si islands (Malachias et al., 2010 ▶), to mention only a few examples. In particular, synchrotron radiation in combination with the forbidden Si or Ge 200 reflection is nowadays used to analyse problems such as the core structure of defects in Si (Richard et al., 2007 ▶), the defect type in patterned Ge/Si islands (Richard, Schülli & Renaud, 2011 ▶ Richard, Malachias et al. For the theoretical description of this phenomenon, also known under the German word Umweganregung, see for example Rossmanith (2000 ▶) and references therein. For a well defined in-plane orientation of the sample (typical Φ rotation on modern diffractometers), multiple diffraction may occur, which makes a forbidden reflection visible or increases or decreases the intensity of allowed reflections depending on Φ. The origin of the appearance of forbidden reflections was discovered and theoretically described by Renninger in 1937 (Renninger, 1937 ▶). Even though the reason for the occurrence of both reflections has been known for many decades, especially concerning the Si 200 reflection daring explanations can still be found in recent publications: for example that it occurs only when the Si lattice is distorted (Zhao et al., 2005 ▶) or that it stems from the Si 400 Bragg reflection of half the wavelength of the Cu Kα radiation (Hesse et al., 2005 ▶). Such measurements very often show a peak of the Si 200 reflection at about 2Θ = 33° for Si(100) substrates and always the Si 222 reflection at about 2Θ = 58.9° for Si(111) substrates, although both reflections are known as basis-forbidden reflections. Typically, the sample alignment is done using the Si 400 or 111 reflection in such a way that during the measurement the diffraction vector is always parallel to the Si or direction, respectively. One standard technique to detect and to study crystalline layers on such substrates is specular X-ray diffraction by ω–2Θ scans using commercially available diffractometers, usually equipped with a Cu anode. To a lesser extent, (111)-oriented Si also finds application. (100)-oriented Si is the most frequently used substrate in microelectronics. X-ray diffraction (XRD) is a well established technique to analyse the crystallographic structure of bulk materials and layers.

$silicon x ray diffraction pattern$

Silicon x ray diffraction pattern