Dr. Andrea Centrone of the National Institute of Standards and Techonology

Dr. Andrea Centrone of the National Institute of Standards and Technology will be presenting "Measuring Chemical Composition, Optical Properties at the Nanoscale with AFM Probes: Application to Plasmonics and Photovoltaics" on February 8, 2017 at 4:10 PM in Neville Hall, Room 003.

Measuring optical and chemical properties at the nanoscale is important for engineering materials in photovoltaics to sensing and other applications. Photo Thermal Induced Resonance (PTIR) is a novel, technique that employs an AFM tip as a local detector to locally transduce the thermal expansion of the sample induced by light absorption into large cantilever oscillations. By leveraging lasers tunable from 500 nm to 16000 nm our PTIR set up yields absorption spectra (electronic or vibrational) and maps with a wavelength-independent resolution as high as 20 nm, extending PTIR to the visible range for the first time. In the first part of the talk I will discuss the PTIR working principles and later some of our recent work on: i) plasmonic and polaritonics nanomaterials ii) organic-inorganic perovskite solar cells.

i) The development of nanostructures that sustain, either sub-diffraction plasmon or phonon-polariton resonances in the mid-IR has generated considerable interest for sensing (via the SEIRA effect) and narrow-band thermal emission, respectively. I will show that PTIR can map the SEIRA enhancement in plasmonic resonators and phonon-polariton modes in hexagonal boron nitride (hBN) nanocones.

ii) Tri-halide perovskites attract interest in photovoltaics because they combine the high efficiency typical of inorganic semiconductors with low material cost and ease of fabrication but their nanoscale properties are not yet well understood. By proving access to the local chemical composition and bandgap PTIR provides unique information to characterize and engineer these materials.

Finally, I will briefly introduce some custom opto-mechanical probes recently developed at NIST that yield a dramatic improvement in the PTIR signal to noise.