title: Near-field Raman dichroism of azo-polymers exposed to nanoscale dc electrical and optical poling.
abstract: Azobenzene-functionalized polymer films are functional materials, where the (planar vs. homeotropic) orientation of azo-dyes can be used for storing data. In order to characterize the nanoscale 3D orientation of the pigments in sub-10 nm thick polymer films we use two complementary techniques: polarization-controlled tip-enhanced Raman scattering (TERS) microscopy and contact scanning capacity microscopy. We demonstrate that the homeotropic and planar orientations of the azo-dyes are produced by applying a local dc electrical field and a resonant longitudinal optical near-field, respectively. For a non-destructive probe of the azo-dye orientation we apply a non-resonant optical near-field and compare the intensities of the Raman-active vibrational modes. We show that near-field Raman dichroism, a characteristic similar to the absorption dichroism used in far-field optics, can be a quantitative indicator of the 3D molecular orientation of the azo-dye at the nanoscale. This study directly benefits the further development of photochromic near-field optical memory that can lead to ultrahigh density information storage.
authors.affiliation: Department of Optics and Nanophotonics, Institute of Physics, Kazan Federal University, Kremlevskaya, 16, Kazan, 420008, Russia. skharint@gmail.com Sergey.Kharintsev@kpfu.ru and Institute of Perspective Technologies, Tatarstan Academy of Sciences, Baumana, 20, Kazan, 420111, Russia.
authors.forename: Sergey S
authors.initials: SS
authors.lastname: Kharintsev
authors.affiliation: Department of Optics and Nanophotonics, Institute of Physics, Kazan Federal University, Kremlevskaya, 16, Kazan, 420008, Russia. skharint@gmail.com Sergey.Kharintsev@kpfu.ru.
authors.forename: Alexandr I
authors.initials: AI
authors.lastname: Fishman
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA and Department of Theoretical Physics, Institute of Physics, Kazan Federal University, Kremlevskaya, 16, Kazan, 420008, Russia.
authors.forename: Semion K
authors.initials: SK
authors.lastname: Saikin
authors.affiliation: Department of Chemical Engineering, Imperial College, London, SW7 2AZ, UK.
authors.forename: Sergei G
authors.identifier: http://orcid.org/0000-0003-1768-9134
authors.initials: SG
authors.lastname: Kazarian