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学术报告（12月7日 周五 10:30-12:00）
主持人：周晓祺 教授
欢迎广大师生前来参与！
【摘要】
Photon signal enhancement by surface plasmon coupling becomes an important issue in super-resolution microscopy and high resolution spectroscopy, such as scanning tunneling microscopy (STM) induced luminescence , surface enhanced Raman spectroscopy, tip enhanced Raman spectroscopy , and so on. This enhancement is varied significantly by the modification of the plasmonic nanocavities. Among these nanocavities, low temperature STM has the most impressive enhanced factor since it can allow us to achieve less than 1nm tip-sample gap stably. This gap-mode plasmonic nanocavity between an STM tip and surface realizes sub-molecular photon spectroscopy . A few works demonstrated that diverse optical transitions can be detected only at atomic scale when they matche a certain resonant mode of the plasmonic nanocavity, which can be modified by tip indentation and showed theoretically that changing the tip aperture causes the resonant peak position variation and the tip apex curvature mainly influences on the luminescence intensity . However, the tip shape dependence of the plasmonic nanocavity remains unclear. In this work, we experimentally present the role of tip shape in surface plasmonic light emission. We have used Ag tips and a Ag(100) substrate, and photon signals have been measured from the different side of the STM tip simultaneously. We dipped STM tips into the substrate with controlling the dipping depth and the lifting speed in order to change the tip shape, and then, the tip shape subsequently was checked through STM profiles. And also, by dropping the small amount of silver atoms from the tip, we examined the dependence of the very apex change. We found that changing small parts of the tip (<3nm tip direction) can differ the photon spectrum significantly and the tendency well agrees with the theoretical model [3]. Furthermore, the plasmonic photon emission from different direction from a STM tip could be quite different due to tip shape asymmetry. This finding can help us to tune the plasmonic photon emission spectra more efficiently and reveal a new experiment idea by using the asymmetric STM tip.
【报告人简介】
Research Field:
- Scanning tunneling microscopy and spectroscopy of nanomaterials and molecules
- STM luminescence and Tip enhanced Raman spectroscopy
- Scanning tunneling microscope scanner design and making
- Ultra high vacuum chamber design
- STM luminescence and tip-enhanced Raman spectroscopy system design and making
- Knudsen cell evaporator and e-beam evaporator design and making
- STM controller and controllers of scanning ion gun, e-beam evaporator tip self-sputtering
- Software for STM control and data analysis
Education:
Sept, 2007 ~ Jul, 2011 Harbin Institute of Technology, China,
bachelor degree
Sept, 2009 ~ Jul, 2010 Pohang University of Science and Technology, Korea, exchange student
Sept, 2011 ~ now Pohang University of Science and Technology, Korea, MS-PHD student
Sept, 2011 ~ Jul, 2013 Study on digital holography
Aug, 2013 ~ now Study on scanning tunneling microscope
Academic activity:
Aug, 2016 Visit Research Center for Applied Science, Academia Sinica, Taiwan
Oct, 2018 AVS 65 symposium oral presentation
Publication:
“Detecting the tip shape dependence of the plasmonic photon emission under STM”, now on paper work.
E-mail: stevencui1989@gmail.com