Cathodoluminescence microscopy: an observer of sub-nanostructures
With tremendous development of nanophotonics and fabrication methods, various micro-nano devices were fabricated, which have potential applications in many aspects, like information processing and quantum communication. Owing to their unique properties, such as light localization and field enhancement, micro-nanostructures have been demonstrated to improve classical optical effect efficiency and device performance. And the control of quantum optical effect also can be achieved. However, due to optical diffraction limit, conventional optical microscopy has a resolution approaching half of light wavelength, which cannot satisfy the demand for quantum studies. Cathodoluminescence microscopy and spectroscopy with sub-nanoscale resolution, has been successfully used in investigations of quantum phenomena at deep subwavelength. Compared with optical illumination, electron beam excitation has advantages of high energy, deep penetration and large exciting power density, which provides a delicate platform for exploring new phenomena and novel properties of sub-nanostructures.
Schematic overview of a CL microscope with angle-resolved function
Professor Zheyu Fang’s group in Peking University is devoted to scientific researches of nanophotonics and cathodoluminescence microscopy in recent years. A series of integrated nanofabrication and detecting equipment, including scanning electron microscopy, cathodoluminescence spectroscopy and electron beam lithography, support independent developments related to nanophotonics. Until now, the group has realized reveal and control of chiral cathodoluminescence at subnanoscale (Nano Lett 18, 567-572 (2018)). By applying different electron impinging positions at Au heptamer, corresponding generated chiral cathodoluminescence emission can be acquired. This phenomenon has been demonstrated to apply in ternary notation information coding. Besides, the group has uncovered deep-subwavelength resolving and manipulating of hidden chirality in achiral nanostructures (ACS nano 12, 3908-3916 (2018)). Cathodoluminescence helicity switch at subnanoscale was also achieved for different electron excitations. These works provide a new insight of chiroptics at subnanoscale and also have potential applications in quantum communication and information coding.
Prof. Fang’s Group: Zheyu Fang is a Professor in School of Physics, Peking University, China, received his PhD in Physics from Peking University with Prof. Xing Zhu, and worked as Postdoc at Rice University with Prof. Naomi J Halas and Prof. Peter J Nordlander. He has published more than 100 peer reviewed papers with 5000 citations. He joined Peking University in 2012 and was selected as the National Top-notch Young Professionals in 2014. His current research interests are plasmonics, near-field optics, and nanophotonic materials and devices.
Liu Z X, Jiang M L, Hu Y L, Lin F, Shen B et al. Scanning cathodoluminescence microscopy: applications in semiconductor and metallic nanostructures. Opto-Electronic Advances 1, 180007 (2018).