贝塞尔电子束具有的自愈性和无衍射性使其在电子显微成像和电子断层扫描等领域中具有独特优势.本文制备了狭缝阵列光阑并安装在透射电子显微镜中用于产生具有自愈性和无衍射性的准贝塞尔电子束(Bessel beams,BBs).与单狭缝法相比,狭缝阵列光阑(slit arrays aperture,SAA)法提高了 BBs的中心束强度并降低衍射旁瓣影响.与普通会聚束相比,BBs被用于扫描透射模式(scanning transmission electron microscopy,STEM)下的高角环形暗场像(high-angle annular dark-field,HAADF),成像时具有更大景深并能修正强度与厚度间的非线性阻尼效应,因而BBs将在易损伤样品拍摄和电子断层扫描中拥有较好的应用前景.
Generation of quasi electron Bessel beams by slit arrays for HAADF-STEM imaging
Bessel electron beams have unique advantages in electron microscopy imaging and tomography due to its self-healing and non-diffraction properties.The slit arrays aperture is prepared and installed in transmission electron microscope to generate quasi Bessel beams(BBs).In this paper,it is verified that the slit arrays method produces non-diffracting and self-healing electron beams.Compared with the single slit method,the center beam intensity of BBs is increased and the influence of side lobes intensity is reduced.It is proved that BBs has larger depth of field and can correct the nonlinear damping effect between intensity and thickness when used in HAADF-STEM imaging compared with ordinary converging beam.Therefore,BBs will have a good application prospect in the imaging of vulnerable samples and electron tomography.
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