電鏡材料檢測方法ppt課件(編輯修改稿)
2025-02-13 18:53 本頁面
【文章內(nèi)容簡介】 re viewed by tilting the specimen. The amount of signals is increased. Use of specimen tilt： a) Dependence of image quality on tilt angle 1) Improving the quality of secondary electron images。 2) Obtaining information different form that obtained when the specimen is not tilted, that is, observing topographic features and observing specimen sides. 3) Obtaining stereo micrographs. Fig. 13 shows a photo taken at a tilt angle of 0176。 (a) and a photo taken at 45176。 (b). Their parison shows that the latter is of smooth quality and stereoscopic as pared with the former. When the specimen is tilted, however lengths observed are different from their actual values. When measuring pattern widths, etc., therefore, it is necessary to measure without specimen tilting or to correct values obtained form a tilted state. (a) Tilt angle: 0176。 (b) Tilt angle: 45176。 Specimen: Back sides of oleaster leaves. More information is obtained from stereopair photos. Use of specimen tilt： b) Stereo micrographs With SEM images it is sometimes difficult to correctly judge their topographical features. In such a case observation of stereo SEM images makes it easy to understand the structure of the specimen. Besides, stereo observation allows unexpected information to be obtained even from specimens of simple structure. In stereo observation, after a field of interest is photographed, the same field is photographed again with the specimen tilted from 5186。 to 15186。. Viewing these two photos using stereo glasses with the tilting axis held vertically provides a stereo image. Use of specimen tilt： c) Detector position and specimen direction The amount of secondary electrons produced when the specimen is illuminated with an electron beam, depends on the angle of incidence theoretically. However, there arises a difference in the image brightness depending on whether the tilted side of the specimen is directed to the secondary electron detector or the opposite side. With a long specimen, for example, the brightness differs between the side facing the detector and the opposite side. In such a case, directing the longitudinal axis of the specimen to the detector makes the brightness uniform. Fig. 16 Specimen: Fiber Detector position and specimen direction. Specimen: Fiber 7kV x2,200 Directing the longitudinal axis of the specimen to the secondary electron detector makes the right and left sides equally bright. (An SRT unit is used to direct the image longitudinally.) Use of specimen tilt： c) Detector position and specimen direction (a) Specimen directed as at 1 (b) Specimen directed as at 2 (c) Specimen directed as at 3 Backscattered electrons vary in their amount and direction with the position, surface topography, crystallinity and magism of the specimen. The contrast of a backscattered electron image depends on (1) the backscattered electron generation rate that depends on the mean atomic number of the specimen, (2) angle dependence of backscattered electrons at the specimen surface, and (3) the change in the backscattered electron intensity when the electron probes incident angle upon a crystalline specimen is changed. Use of backscattered electron signals ? 背散射
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