第四章扫描电子显微镜及电子探针讲义.ppt

本章主要内容 　概述 电子束和固体样品作用时产生的信号 　SEM结构及成象原理 　SEM的主要性能 　样品制备 　二次电子衬度原理及其应用 　背散射电子衬度原理及其应用 能谱分析和波谱分析 Influence of edge effect on image quality Edge effect (secondary electron emission differing with surface condition). Influence of edge effect on image quality Specimen IC chip. The higher the accelerating voltage, the greater is the edge effect, making the edges brighter. Use of specimen tilt：a) Dependence of image quality on tilt angle Specimen: IC chip. 5 kV x1,100 The sides of patterns are viewed by tilting the specimen. The amount of signals is increased. Use of specimen tilt：b) Stereo micrographs Specimen: Back sides of oleaster leaves. More information is obtained from stereo-pair photos. The effect of Accelerating Voltage on SEM Images Specimen: Toner 墨粉 When high accelerating voltage is used as at (a), it is hard to obtain the contrast of the specimen surface structure. Besides, the specimen surface is easily charged up. The surface microstructures are easily seen at (b). Specimen: Evaporated Au particles. The image sharpness and resolution are better at the higher accelerating voltage, 25 kV. Specimen: Filter paper. At 5 kV, the microstructures of the specimen surface are clearly seen as the penetration and diffusion area of incident electrons is shallow. Fig. 6 Specimen: Sintered powder. At low accelerating voltage, while surface microstructures can be observed, it is difficult to obtain sharp micrographs at high magnifications. In such a case, clear images can be obtained by shortening the WD or reducing the electron probe diameter. Specimen: Paint coat. When a high accelerating voltage is used, more scattered electrons are produced from the constituent substances within the specimen. This not only eliminates the contrast of surface microstructures, but produces a different contrast due to backscattered electrons from the substances within the specimen. SE (secondary electron) imaging SEM Compositional image Backscattered SEM image of an PbSn alloy show