扫描电镜与投射电镜（Scanning electron microscopy and projection electron microscopy）.docVIP

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扫描电镜与投射电镜（Scanning electron microscopy and projection electron microscopy）.doc

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扫描电镜与投射电镜（Scanning electron microscopy and projection electron microscopy）

扫描电镜与投射电镜（Scanning electron microscopy and projection electron microscopy） 1) detector X ray spectrometer WDS The principle is basically the same as the X-ray fluorometer, but using electrons instead of x-rays as the source of the shock. The X-ray spectrometer is characterized by high resolution, usually 5-10ev, and can work at room temperature, so the accuracy of the analysis is high and the test limit is low. In addition, according to the Bragg theorem 2dsin theta = lambda, the crystal of crystal spacing d is used to analyze the light elements, such as boron, carbon, nitrogen and oxygen, which identify the wavelength of X ray. However, the X-ray spectrometer has its limitations, and its spectral crystal accepts X rays with low cubiage, and the X-ray utilization is low. In addition, the sample requires the surface to be smooth and clean like gold samples, and cannot analyze the uneven samples. The principle EDS for lithium drift silicon detector When the photon enters the detector, a certain number of electron hole pairs are excited in the Si (Li) crystal. The lowest average energy epsilon that produces a hole is certain, so the number of holes caused by an X-ray photon is equal to delta E/epsilon. The higher the energy of the incident X-ray photon, the greater the N. By using the bias on both ends of the crystal to collect the electron hole pairs, the preamplifier is converted to the current pulse, and the height of the current pulse depends on the size of N. Current pulse through the main amplifier converts voltage pulse into the multi-channel pulse height analyzer, pulse height analyzer according to height to classify the pulse count, so we can trace a X-ray energy size distribution map. Analysis features of EDS spectrometer: The spectrometer detects X-ray efficiency. At the same time to analyze all the elements within the X-ray photon energy measuring and counting, qualitative analysis results can be obtained in a few minutes, the spectrometer can measure each