November 15th
when: Thursday 15/11/2018, 10:30
where: KE E-541 (møterom)
speaker: Michael C. Martin (Photon Science Operations Group Leader, Advanced Light Source, Berkeley)
title: Synchrotron Infrared Nano Spectroscopy
abstract:
Scattering scanning near-field optical microscopy (s-SNOM) has emerged as a powerful imaging and spectroscopic tool for investigating nanoscale heterogeneities in biology, quantum matter, and electronic and photonic devices. However, many materials are defined by a wide range of fundamental molecular vibrations and quantum states at mid- and far-infrared resonant frequencies currently not accessible by s-SNOM. Here we show ultrabroadband IR s-SNOM nano-imaging and spectroscopy by combining synchrotron infrared radiation with a customized AFM or a Neaspec system with a fast MCT or a novel fast and low-noise copper-doped germanium (Ge:Cu) photoconductive detector [1]. This approach of Synchrotron Infrared Nano Spectroscopy (SINS) exceeds conventional limits [2] by an octave toward lower energies. We demonstrate this new nano-spectroscopic window by measuring elementary excitations of exemplary functional materials, including surface phonon-polariton waves and optical phonons in oxides and layered ultrathin van der Waals materials, skeletal and conformational vibrations in molecular systems, and the highly tunable plasmonic response of graphene. This work highlights the continued advantage of synchrotron radiation as an ultrabroadband coherent light source for near-field nano-spectroscopy, especially in the long wavelength regime where alternative low-noise, broadband, quasi-cw laser sources are not readily available.
References
[1] Khatib, Bechtel, Martin, Raschke, Carr, ACS Photonics, 5(7), 2773–2779(2018).
[2] Bechtel, Muller, Olmon, Martin, Raschke, PNAS 111(20), 7191–7196 (2014).
Slides: can be downloaded here.