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Observation of high resolution elemental mapping images using a high sensitivity detector

使用高灵敏度探测器观察高分辨率元素映射图像

基本信息

批准号：
04452103
负责人：
HIBINO Michio
金额：
$ 4.03万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

1. Development of a dedicated detector for elemental mapping(1) Construction of a detection system : In order to realize a fast elemental mapping, which displays images of elemental concentration, by use of the parallel electron energy loss spectroscopy (PEELS) and the scanning transmission electron microscopy (STEM), a moderate-scale photodiode arrray (PDA) of 35 channel was used to acquire energy loss spectra. Electric circuits and computer programs were also developed to control the elemental mapping system. Spectrum acquisition time for one pixel is 1.2 msec which is 20 times shorter than that of conventional 1024 channel PDA.(2) Measurements of fundamental properties of the detector : A windowless PDA was prepared to decrease the leakage of light from the electron scintillator in transmission from the window to elements of the PDA, and the cross talk was reduced to 4 % of total output current of the PDA.Measurement of the detective quantum efficiency (DQE) of the detector showed that the DQE decreases in a low electron intensity region, where the elemental mapping is usually carried out, due to electromagnetic disturbance. This result indicates that more effective electromagnetic shield is required.2. Achievement of high current density electron probe by spherical aberration correctionIn order to obtain high resolution elemental mapping images, spherical aberration of the probe-forming lens was corrected with a foil lens. It was found, theoretically and experimentally that the foil lens allows a high current density and should be useful for a low intensity spectrum.3. Observation of elemental mapping imagesIn elemental mapping images of boron nitride on a carbon microgrid, the microgrid and the boron intride were clearly discriminated. With nickel oxide, which have excitation edges in a high energy loss and low intensity region, elemental mapping images were observed as a result of the high sensitivity of the detector.

1.（1）探测系统的构建：为了实现快速元素定位，利用并行电子能量损失谱（PEELS）和扫描透射电子显微镜（STEM），利用35通道的中尺度光电二极管阵列（PDA）获取能量损失谱，并显示元素浓度图像。还开发了电路和计算机程序来控制元素映射系统。一个像素的光谱采集时间为1.2毫秒，比传统的1024通道PDA短20倍。(2)探测器基本特性的测量：设计了一种无窗PDA，以减少电子闪烁体的光从窗口到PDA元件的泄漏，使串扰降低到PDA总输出电流的4%。测量了探测器的量子探测效率（DQE），发现在低电子强度区DQE降低，其中由于电磁干扰，通常执行元素映射。这一结果表明需要更有效的电磁屏蔽.用球差校正法实现高电流密度电子探针为了获得高分辨率的元素分布图像，用箔透镜校正了探针形成透镜的球差。从理论和实验上发现，箔透镜允许高电流密度，并应适用于低强度光谱。3.在碳微网格上的氮化硼的元素映射图像中，可以清楚地区分微网格和氮化硼。对于在高能量损失和低强度区域中具有激发边缘的氧化镍，由于检测器的高灵敏度，观察到元素映射图像。