Differential interference contrast microscopy technique

Powerful methods that have been developed more recently, and are currently used to observe surface micro topographs of crystal faces, include scanning tunnel microscopy (STM), atomic force microscopy (AFM), and phase shifting microscopy (PSM). Both STM and AFM use microscopes that (i) are able to detect and measure the differences in levels of nanometer order (ii) can increase two-dimensional magnification, and (iii) will increase the detection of the horizontal limit beyond that achievable with phase contrast or differential interference contrast microscopy. The presence of two-dimensional nuclei on terraced surfaces between steps, which were not observable under optical microscopes, has been successfully detected by these methods [8], [9]. In situ observation of the movement of steps of nanometer order in height is also made possible by these techniques. However, it is possible to observe step movement in situ, and to measure the surface driving force using optical microscopy. The latter measurement is not possible by STM and AFM. 

Hie most important optical technique for examining semiconductor wafer surfaces is the differential interference contrast microscopy method of Nomarski (N-DIC). First described in 1952, DIG... 

More advanced (and expensive) microscopy techniques are differential interference contrast microscopy and laser scanning confocal microscopy. The latter can provide precise optical sectioning so that three-dimensional images of stmctures can be recorded. 

In video microscopy, for instance, background is normally subtracted using differential interference contrast (DIC) [18]. This technique, which requires a number of manipulations from the user, may now be automated using a new method called polarization-modulated (PMDIC) [19,20], It requires the introduction of a liquid crystal electro-optic modulator and of a software module to handle difference images. PMDIC has been shown to bring improvements in imaging moving cells, which show a low contrast, as well as thick tissue samples. 

Contrast. See also Differential interference contrast (DIC) computer-assisted, 16 487 in microscopy, 16 474 techniques for improving, 16 474-487... 

A EXPERIMENTAL FIGURE 5-44 Live cells can be visualized by microscopy techniques that generate contrast by interference. These micrographs show live, cultured macrophage cells viewed by bright-field microscopy (/eft), phase-contrast microscopy middle), and differential interference contrast (DIC) microscopy righti. In a phase-contrast image, cells... 

Another technique for crystallinity analysis is the measurement of pole figures. It is widely applied for thin films, LPE films, melt-processed polycrystalline samples with a noticeable texture (Goyal et al. 1993). In fig. 33, a good crystallinity of the Y123 LPE film is evidently obtained due to a specific growth mechanism, mentioned above (sect. 5.4), despite the large misfit between the film and the MgO substrate. Differential interference contrast (DIM or Nomarski) microscopy can be successfully applied to observe misorientation on flat ( mirror-like ) surfaces (Klemenz and Scheel 1993). 

Later, differential interference microscopy was developed, enabling the detection of difference in levels as sensitively as phase contrast microscopy, and, because this technique was easier to use, it came to be used in preference to the former techniques [6]. Differential interference microscopy is superior to phase contrast microscopy in the observation of vicinal or curved surfaces, which are impossible to observe under a phase contrast microscope because the contrast is too high. 

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