Department of Physics, Arizona State University, Tempe, AZ 85287-1504, USA.
Micron. 2016 Apr;83:79-92. doi: 10.1016/j.micron.2016.02.007. Epub 2016 Feb 11.
Electric fields can be induced by electron irradiation of insulating thin film materials. In this work, the electric fields under a broad beam illumination in transmission electron microscopy (TEM) are analyzed for insulating samples. Some damage phenomena observed can be interpreted by the mechanism of damage by the induced electric field (DIEF). For broad-beam illumination in an ultra-thin specimen, the electric field near the center of the illumination may not be strong, but at the periphery of the illumination the electric field can be significant. Therefore, damage may be easily observed in these regions rather than at the center of the illumination. For a beam which is broad compared to the specimen thickness, e.g. 100∼1000nm, a strong electric field pointing inward into the specimen near the surface region may result in cation diffusion into the specimen and/or anion diffusion out to the surface region. Meanwhile, a strong electric field perpendicular to the beam direction near the edge of the illumination may attract anions into the illuminated region, but eject cations to the periphery. For a wedge-shaped specimen, the electric field points inward into thicker region, driving cations toward the thicker region, while attracting anions to the edge region. On the sharp edge, a strong electric field pointing outward may be responsible for the edge-smoothing effect observed in insulating materials.
电场可以通过电子辐照绝缘薄膜材料来产生。在这项工作中，分析了透射电子显微镜（TEM）中宽束照明下的电场，用于研究绝缘样品。通过感应电场（DIEF）损伤机制，可以解释一些观察到的损伤现象。对于超薄膜的宽束照明，照明中心附近的电场可能不强，但在照明的外围，电场可能很显著。因此，损伤可能很容易在这些区域观察到，而不是在照明的中心。对于与样品厚度相比较宽的光束，例如 100∼1000nm，在表面区域附近的样品内部指向内部的强电场可能导致阳离子扩散到样品中，和/或阴离子扩散到表面区域。同时，在照明边缘附近垂直于光束方向的强电场可能会将阴离子吸引到照明区域，但将阳离子排斥到边缘区域。对于楔形样品，电场指向较厚的区域内部，将阳离子推向较厚的区域，同时将阴离子吸引到边缘区域。在尖锐的边缘，指向外部的强电场可能是导致绝缘材料中观察到的边缘平滑效应的原因。
