TEM SEM The optics of image Projection of the Collection of point by formation transmitted beam onto a point signal of a focused phosphor screen to form beam scanned across the an enlarged image. specimen. Depth of field/depth of Depth of field exceeds the Depth of field is typically focus resolution by 2 orders of of the order of a couple of magnitude. um to hundreds of um considerably better than in OM Specimen shape and Thin foil specimen A large variety of dimensions transparent to electron. specimen can be used. 26
TEM vs SEM 26 TEM SEM The optics of image formation Projection of the transmitted beam onto a phosphor screen to form an enlarged image. Collection of point by point signal of a focused beam scanned across the specimen. Depth of field/depth of focus Depth of field exceeds the resolution by 2 orders of magnitude. Depth of field is typically of the order of a couple of m to hundreds of m considerably better than in OM Specimen shape and dimensions Thin foil specimen transparent to electron. A large variety of specimen can be used
TEM SEM LVJ Electron gun L」 Electron gun Vacuum 密 Condenser system Condenser lens column Scan coils Stage Time Also tilts and rotates base Objective lens Probe lens Signal amplifier Final imaging system Stage Also tilts and rotates Detector and Observation processing and recording system system CRT In the SEM you use secondary signals to acquire images. 27 Adapted from the lecture notes of Prof.Mark L.Weaver,The University of Alabama
27 Adapted from the lecture notes of Prof. Mark L. Weaver, The University of Alabama
扫描电镜成像基础
扫描电镜成像基础
样品的衬度 扫描电镜衬度的形成主要基于样品微区诸如表面形貌、原子序数或化学成分、 晶体结构或取向等方面存在着差异。入射电子与之相互作用，产生各种特征信号( 二次电子，背散射电子，吸收电子等)，其强度就存在着差异，最后反映到显像管 荧光屏上的图像就有一定的衬度。 形貌衬度 成分衬度
扫描电镜成像基础 样品的衬度 扫描电镜衬度的形成主要基于样品微区诸如表面形貌、原子序数或化学成分、 晶体结构或取向等方面存在着差异。入射电子与之相互作用，产生各种特征信号( 二次电子，背散射电子，吸收电子等)，其强度就存在着差异，最后反映到显像管 荧光屏上的图像就有一定的衬度。 形貌衬度 成分衬度
入射电子与样品的相互作用 入射电子束 X射线 (元素信息) 背散射电子 (凹凸/成分，晶向信息) 俄歇电子 (表层元素信息) 阴极荧光 二次電子 (化合结合状态信息) (表面形貌信息) 品 EBIC--电子束感生 样品电流 电流（半导体PN节定位 (成分信息) 及损伤研究) 透過散乱 17 电子 透過电子(STEM像，成分和厚度信息)
入射电子与样品的相互作用 扫描电镜成像基础