报告题目：Peak force scattering-type near-field optical microscopy for correlative and three-dimensional near-field imaging at sub 10 nm spatial resolution
报告人：Dr. Xiaoji Xu, Lehigh University
时间：2019-06-04 10:00
地点：卢嘉锡楼202报告厅
报告摘要：
Scattering-type scanning near-field optical microscopy (s-SNOM) provides nanoscale spectroscopic imaging and has been instrumental for many nano-photonic discoveries and in-situ studies of a wide range of materials, most notably plasmonics and polaritonic low dimensional materials. The metallic tip localizes the radiation underneath the tip to excited resonance in the sample. The high field density of states also assists the scattering of the near-field signal for amplification. However, conventional s-SNOM techniques with tapping mode operation and lock-in detections does not provide direct tomographic information at explicit tip-sample distance. In this seminar, we present a non-traditional s-SNOM technique, peak force scattering-type scanning near-field optical microscopy (PF-SNOM), by the combination of peak force tapping mode and temporally gated detection. The method enables direct sectioning of vertical near-field signals from the sample surface for both three-dimensional near-field imaging and spectroscopic analysis. Tip-induced relaxation of the surface phonon polaritons are revealed and described with a model. PF-SNOM also delivers a substantially improved spatial resolution of 5 nm and is capable of simultaneously acquiring mechanical and electrical properties together with near-field optical signals. PF-SNOM extends the capability of s-SNOM and is expected to facilitate nanoscale optical characterizations and investigations on light-matter near-field interactions.
报告人简介：
Xiaoji Xu established his research group since 2014 as an assistant professor in the department of chemistry at Lehigh University in Bethlehem, Pennsylvania, United States. Before at Lehigh University, he was a postdoctoral fellow at the University of Toronto, and University Colorado Boulder. He received his B.S. in Chemistry from Peking University in 2004 and Ph.D. from The University of British Columbia, Vancouver, Canada in 2009. His research focuses are on chemical sensitive nanoscale imaging, ultrafast laser spectroscopy, and development of the analytical instrumentation for chemical measurement. He holds several patents on nanoscale infrared microscopy. Since his independent career, he has published nine papers as the corresponding author, including Nat. Commun., Sci. Adv., ChemComm., and ACS Photonics. Dr. Xu was featured as one of Emerging Investigators by Chemical Communications in 2017. He was selected as a Beckman Young Investigator by Arnold and Mabel Beckman Foundation in 2018. He is also a recipient of the NSF CAREER award in 2019.
