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Diffraction topography (short: "topography") is an quantum beam imaging technique based on Bragg diffraction. Diffraction topographic images ("topographies") record the intensity profile of a beam of X-rays (or, sometimes, neutrons) diffracted by a crystal. A topography thus represents a two-dimensional spatial intensity mapping of reflected X-rays, i.e. the spatial fine structure of a Laue reflection. This intensity mapping reflects the distribution of scattering power inside the crystal; topographs therefore reveal the irregularities in a non-ideal crystal lattice. X-ray diffraction topography is one variant of X-ray imaging, making use of diffraction contrast rather than absorption contrast which is usually used in radiography and computed tomography (CT). Topography is exploited to a lesser extends with neutrons and other quantum beams. In the electron microscope community, such technique is called dark field imaging or diffraction contrast imaging. Topography is used for monitoring crystal quality and visualizing defects in many different crystalline materials. It has proved helpful e.g. when developing new crystal growth methods, for monitoring growth and the crystal quality achieved, and for iteratively optimizing growth conditions. In many cases, topography can be applied without preparing or otherwise damaging the sample; it is therefore one variant of non-destructive testing. == History == After the discovery of x-rays by Wilhelm Röntgen in 1895, and of the principles of X-ray diffraction by Laue and the Bragg family, it still took several decades for the benefits of diffraction ''imaging'' to be fully recognized, and the first useful experimental techniques to be developed. First systematic reports on laboratory topography techniques date from the early 1940s. In the 1950s and 1960s, topographic investigations played a role in detecting the nature of defects and improving crystal growth methods for Germanium and (later) Silicon as materials for semiconductor microelectronics. For a more detailed account of the historical development of topography, see J.F. Kelly - "A brief history of X-ray diffraction topography".〔http://img.chem.ucl.ac.uk/www/kelly/historyoftopography.htm〕 From about the 1970s on, topography profited from the advent of synchrotron x-ray sources which provided considerably more intense x-ray beams, allowing to achieve shorter exposure times, better contrast, higher spatial resolution, and to investigate smaller samples or rapidly changing phenomena. Initial applications of topography were mainly in the field of metallurgy, controlling the growth of better crystals of various metals. Topography was later extended to semiconductors, and generally to materials for microelectronics. A related field are investigations of materials and devices for X-ray optics, such as monochromator crystals made of Silicon, Germanium or Diamond, which need to be checked for defects prior to being used. Extensions of topography to organic crystals are somewhat more recent. Topography is applied today not only to volume crystals of any kind, including semiconductor wafers, but also to thin layers, entire electronic devices, as well as to organic materials such as protein crystals and others. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Diffraction topography」の詳細全文を読む スポンサード リンク
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