"Circumventing the diffraction limit with synchrotron infrared nano-spectroscopy"
The Advanced Light Source (ALS) at the Lawrence Berkeley National Laboratory is a Department of Energy User Facility which provides spectrally broad light for chemical analysis and imaging of materials. The infrared beamlines at the ALS take advantage of the high brightness and spatial coherence of the source to perform label-free spectroscopic imaging of novel materials and unique samples from the bottom of the ocean to the depths of space, and everywhere in between. The long wavelengths of infrared light have traditionally limited the spatial resolution of far-field infrared techniques to the micron scale; however, the development of near-field methods have enabled infrared analysis to surpass the diffraction-limit and probe chemical and physical heterogeneities at the nanoscale. Synchrotron infrared nano-spectroscopy (SINS) combines the synchrotron infrared source characteristics with scattering-type, scanning near-field optical microscopy (s-SNOM). By focusing and scattering synchrotron light off a metallic AFM tip in close proximity to the sample, the SINS technique dramatically improves the spatial resolution several orders of magnitude (< 25 nm) while enabling sensitive spectroscopy across the entire mid- and far-infrared regions. The ALS operates two beamlines with SINS instruments which are available to general users. In this talk, I will describe the technical aspects of the method as well as highlight several applications to soft and hard matter systems; including proteins, organic semiconductors, catalysts, 2D materials, and phase-change materials [1-5] in which nanoscale chemical specificity was critical to resolving the reported electronic, optical, and thermal effects.
 H.A. Bechtel, E.A. Muller, R.L. Olmon, M.C. Martin, M.B. Raschke, PNAS 111, 7191–7196 (2014).
 E. A. Muller, B. Pollard, H. A. Bechtel, P. van Blerkom, M. B. Raschke. Science Advances, 2 (10), e1601006 (2016).
 C. Y. Wu, W. J. Wolf, Y. Levartovsky, H. A. Bechtel, M. C. Martin, F. D. Toste, Nature 541 (7638), 511 (2017).
 S. N. Gilbert Corder, et al. Nature Communications, 8, 2262 (2017).
 Z. Hao, H. A. Bechtel, T. Kneafsey, B. Gilbert, P. S. Nico, Scientific Reports, 8, 2552 (2018).
Acknowledgements: This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231.