《電鏡材料檢測方法》ppt課件-全文預(yù)覽
【正文】 f edge effect on image quality Among the contrast factors for secondary electrons, the tilt effect and edge effect are both due to the specimen surface morphology. Secondary electron emission from the specimen surface depends largely on the probe’s incident angle on the specimen surface, and the higher the angle, the larger emission is caused. The objects of the SEM generally have uneven surfaces. There are many slants all over them, which contribute most to the contrast of secondary electron images. On the other hand, large quantities of secondary electrons are generated from the protrusions and the circumferences of objects on the specimen surface, causing them to appear brighter than even portions. Specimen IC chip. The higher the accelerating voltage, the greater is the edge effect, making the edges brighter. Influence of edge effect on image quality The degree of the edge effect depends on the accelerating voltage. Namely, the lower the accelerating voltage, the smaller the peration depth of incident electrons into the specimen. This reduces bright edge portions, thus resulting in the microstructures present in them being seen more clearly. Normally, secondary electron images contain some backscattered electron signals. Therefore, if the tilt direction of the specimen surface and the position of the secondary electron detector are geometrically in agreement with each other, more backscattered electrons from the tilted portions are mixed, causing them to be seen more brightly due to synergism. (a) 5 kV x720 Tilt Angle: 50176。 因為電子束穿入樣品激發(fā)二次電子的有效深度增加了，使表面510 nm作用體積內(nèi)逸出表面的二次電子數(shù)量增多。 ? 特 征： ? 1)二次電子能量較低。 由于原子核和外層價電子間的結(jié)合能很小，因此，外層的電子較容易和原子脫離，使原子電離。 電子束進入 輕 元素樣品 滴狀 作用體積 電子束進入 重 元素樣品 半球狀 作用體積 SEM的分辨率即二次電子相的分辨率 電子束進入重元素樣品后，立即向橫向擴展，因此在分析重元素時，即使電子束的束斑很細小，也不能達到較高的分辨率，此時二次電子和背散射電子之間的分辨率的差距明顯變小。 第一個掃描電鏡裝置 劍橋大學， 1951年 第一臺商用掃描電鏡 High Resolution Field Emission SEM SEM images have a natural 3D look And now a look inside the SEM…. SEMScanning Electron Microscope (or microscopy) TEM Transmission Electron Microscope AEM Analytical Electron Microscope STEM Scanning Transmission Electron Microscope EPMAElectron Probe MicroAnalyzer SPMScanned Probe Microscope (STM, AFM) To see a VIRTUAL SEM, go to the following link: SEM 的構(gòu)造 氣動保險閥 掃描線圈 Signals available from SEM Signals SEM的主要性能： 1，分辨率 二次電子和俄歇電子的分辨率高，特征 X射線調(diào)制成顯微圖像的分辨率最低。這也是一種真空自由電子 。其中90%來自于外層價電子。 成像原理 二次電子產(chǎn)額對微區(qū)表面的幾何形狀十分敏感，如圖所示，隨入射束與試樣表面法線夾角增大，二次電子產(chǎn)額增大。 3)在深的凹槽底部盡管能產(chǎn)生較多二次電子，使其不易被控制到，因此相應(yīng)襯度也較暗。 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。 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
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