Materials & Surface Science Institute, University of Limerick, Limerick, Ireland.
Phys Chem Chem Phys. 2011 Jan 21;13(3):1189-200. doi: 10.1039/c0cp01141j. Epub 2010 Nov 15.
A transmission electron microscope was used to characterize a powder form of hexagonally-ordered mesoporous silica material. The structural symmetry built into this amorphous material allowed one to obtain three characteristic images, i.e. a hexagonal honey-comb structure and wide/narrow parallel lines. These images were found to originate primarily from phase contrast, which changed sensitively with defocusing. To further understand the contrast behaviour of these images, an analytical form of the defocus contrast theory was developed and applied to the simulation of the characteristic wide/narrow parallel line images. The simulation was found to be in good qualitative agreement with experiments, where changes in focus conditions and specimen thickness were predicted to alter the contrast in the resulting parallel-line type images.
利用透射电子显微镜对六方有序介孔硅材料的粉末形式进行了表征。这种无定形材料中内置的结构对称性使得人们能够获得三种特征图像，即六方蜂窝结构和宽/窄平行线。这些图像主要源于相位对比，相位对比对离焦变化非常敏感。为了进一步了解这些图像的对比行为，开发了一种离焦对比理论的解析形式，并将其应用于特征宽/窄平行线图像的模拟。模拟结果与实验具有很好的定性一致性，预计改变聚焦条件和样品厚度会改变所得平行线类型图像的对比度。
