Research on High Resolution Electron Microscope Observations without Specimen Damage

1.高压扫描电子显微镜用场发射电子枪在改进真空系统和建立监控系统的基础上，将场发射电子枪安装在100OKV扫描电子显微镜上，对电子枪的工作状态进行监控。采用&lt；310&gt；取向的钨电极，获得了大于50muA的稳定场发射。各种信号电子的探测一种用于高灵敏度电子探测器的新型YAG单晶闪烁体，其灵敏度是传统粉末荧光粉闪烁体的10倍。通过对电子能量分析系统的改进，建立了高精度探测非弹性散射和非散射电子的方法。信号处理对提高样品结构图像质量的理论研究揭示了在弹性散射、弹性…更多的散射和未散射的电子。通过开发有效的数据采集接口和各种电子信号之间的处理系统，建立了信号处理系统。将信号处理应用于实际的电子显微镜观察，验证了信号处理在消除噪声、增强特定样品结构对比度、识别组成元素等方面的有效性。照射电子的电流密度对样品损伤的影响及高分辨无损伤观察对正三十烷电子衍射图强度变化的研究表明，高电流密度的精细电子探针的STEM照射比低电流密度的常规电子显微镜的长时间照射对样品的损伤更小。研究还发现，对于碳膜中的细小铂颗粒，在常规的电子显微镜模式观察中，容易受到迁移、附着和结晶损伤的高分辨率扫描电子显微镜观察是可能的，而不会造成样品损伤。较少

1. Field emission electron gun for high voltage scanning transmission electron microscope A field emission electron gun was mounted on the 10OOkV scanning transmission electron microscope (STEIM), after improving a vacuum system and establishing a monitor-control system for monitoring and controlling the operating condition of the gun. A stable field emission of more than 50muA was obtained with a <310> orientation tungsten tip.2. Detection of various signal electrons A new YAG single crystal scintillator was developed for high-sensitivity electron detector which gives the sensitivity of 10 times as much as a conventional powdered-phosphor scintillator. A method was established as well for detecting inelastically scattered and unscattered electrons with high accuracy, by improving an electron energy analyzing system.3. Signal manipulation A theoretical investigation for better image quality of specimen structure revealed an appropriate manipulation among elastically scattered, inelasti … More cally scattered and unscattered electrons. A signal manipulation system was established by developing an interface for effective data acquisition and a system for manipulating among various electron signals. Signal manipulation was then applied to practical electron microscope observations, which verified the effectiveness of signal manipulation for noise elimination, contrast enhancement of specific specimen structure, identification of constituting elements and so on.4. Influence of current density of illumination electrons on the specimen damage and high resolution observations without damage Studies on intensity change of electron diffraction pattern of hexatriacontane indicated that STEM illumination with a fine electron probe of high current density gives less specimen damage than long-time illumination of conventional electron microscopy with low current density. It was found as well that high resolution STEM observations without specimen damage are possible for fine platinum particles in a carbon film which are easily subject to damage of migration, adhesion and crystallization in conventional electron microscopy mode observations. Less