哈工大-sem实验报告.doc

《先进材料表征技术》课程 学生实验报告 实验名称： 扫描电镜与能谱仪的原理及应用 姓 名： 实验时间： 2015 年 11 月 6 日 哈尔滨工业大学深圳研究生院  1. Be familiar with the structure and principle of scanning electron microscope . 2. Be familiar with the requirement of sample preparation. 3. Know about the operation specification of SEM, be familiar with the differences between image of secondary electron and backscatter electron. 4. Know about the operation specification of EDS, be familiar with the point analysis, line analysis and mapping. II. Principles 2.1Resolution and contrast For imaging, resolution means the minimum distance between two distinct points.For composition analysis, resolution means the minimum region can be analyzed. In SEM system, resolution depends on the diameter of the incident electron beam and signal type. Contrast means the difference of brightness , and it can be caused by morphology or atomic number. The morphology contrast is always observed in SE image, and the atomic contrast is always observed in BSE image. 2.2 Electron microscopy imaging The beam emitted from the electron gun is focused at the surface of the sample through a series of electromagnetic lens (Fig 1.). The last lens equipped with a scanning coil can drive electron beam scan on the surface. The interaction between high energy electron beam and sample generate various signals, and the signals can be received by the detector. Do this point by point and we can get a image (Fig 2.). Fig 1. Fig 2. the scanning process to form a image 2.3 SE image and BSE image Secondary electron signal are generated from the very surface (Fig 3.), so the intensity of the signal sensitive to the orientation of the incident beam. Along angle formed by surface and incident beam increases, the secondary electron yield increase. Therefore, the SE image is suitable for display the morphology contrast. From Fig 2. we can see that backscatter electron is generated from a relative big volume near to the surface,