Rose H, Fertig J
Ultramicroscopy. 1976 Dec;2(1):77-87. doi: 10.1016/s0304-3991(76)90518-0.
Plural electron scattering within thick objects broadens and smoothes the intensity distribution in the detector plane of a scanning transmission electron microscope. Detector arrangements have been determined which give maximum contrast and optimum S/N when the object details are large compared to the scanning spot. Asymptotic expressions for the optimum detector angles, specimen resolution, and S/N were obtained which are valid for objects thicker than approximately four elastic mean free path lengths. Exact calculations of the changes in contrast and S/N with thickness fluctuations in amorphous carbon foils were performed for atbitrary foil thicknesses. Elastic and inelastic electron scattering was taken into account.
厚样品内的多次电子散射会使扫描透射电子显微镜探测器平面上的强度分布变宽和平滑。当样品细节尺寸远大于扫描光斑时，已确定了能给出最大对比度和最佳信噪比的探测器配置。得到了最佳探测器角度、样品分辨率和信噪比的渐近表达式，这些表达式对于厚度大于约四个弹性平均自由程长度的样品是有效的。针对任意厚度的非晶碳箔，精确计算了对比度和信噪比随厚度波动的变化情况。计算中考虑了弹性和非弹性电子散射。
