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Generation and manipulation of phonon polaritons are of paramount importance for understanding the interaction between an electromagnetic field and dielectric materials and furthering their application in mid-infrared optical communication. However, the formation of tunable one-dimensional phonon polaritons has been rarely realized in van der Waals layered structures. Here we report the discovery of curvature-induced phonon polaritons localized at the crease of folded hexagonal boron nitrides (

This program was focused on several novel experimental approaches to investigating charge injection and charge transport in organic semiconductors all using infrared (IR) spectroscopy. IR spectroscopy was employed to characterize polymer systems integrated in the architecture of organic field-effect transistors (OFET). These experiments allowed the PI to determine: i) the excitations of the studied organic semiconductors, and ii) their dynamics in high mobility OFETs. The PI proposed to investigate modification of the electronic properties at the surface of organic semiconductors controlled by self-assembled monolayers (SAM) and has completed this work. In addition, the PI has completed a comprehensive study of high mobility, low band gap of Donor-Acceptor (D A) copolymers that are of high interest in view of ambipolar transport in these systems.

We report on infrared (IR) nanoscopy of 2D plasmon excitations of Dirac fermions in graphene. This is achieved by confining mid-IR radiation at the apex of a nanoscale tip: an approach yielding 2 orders of magnitude increase in the value of in-plane component of incident wavevector q compared to free space propagation. At these high wavevectors, the Dirac plasmon is found to dramatically enhance the near-field interaction with mid-IR surface phonons of SiO(2) substrate. Our data augmented by detailed modeling establish graphene as a new medium supporting plasmonic effects that can be controlled by gate voltage.

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