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SUMMARY:AFM-Raman-SNOM and Tip Enhanced Raman imaging studies of modern na
 nostructures - . Pavel Dorozhkin\, NT-MDT Co
DTSTART:20110202T110000Z
DTEND:20110202T120000Z
UID:TALK29668@talks.cam.ac.uk
CONTACT:Sumeet Mahajan
DESCRIPTION:We demonstrate instrumental realization and various applicatio
 ns of Atomic Force Microscopy integrated with\nConfocal Raman/Fluorescence
 /Rayleigh microscopy and Scanning Near Field Optical Microscopy (SNOM)\npr
 oduced by NT-MDT. Results on various samples are demonstrated: graphene\, 
 carbon nanotubes\,\nsemiconductor nanowires\, quantum dots\, nanodiamonds\
 , plasmonic waveguides\, photonic crystal optical fibers\,\nvarious biolog
 ical objects etc.\nFor example\, graphene on gold is investigated by diffe
 rent AFM and spectroscopy techniques providing\ncomprehensive information 
 about the sample. We study in details how the thickness (number of monolay
 ers) in\ngraphene affects its physical properties: surface potential (work
  function)\, local friction\, elastic modulus\,\ncapacitance\, conductivit
 y\, charge distribution\, Raman and Rayleigh light scattering etc. Results
  for graphene\nflakes are qualitatively compared to those for carbon nanot
 ubes of different diameters. We show how\nelectrostatic charging of graphe
 ne flakes can be effectively measured and modified by AFM cantilever. Stud
 ies\nare performed both in ambient air conditions and in controlled atmosp
 here and humidity.\n\nWe also present results of Tip Enhanced Raman Spectr
 oscopy (TERS) or “nano-Raman” mapping realized\nusing integrated AFM-R
 aman system. Measurements are realized in two different excitation configu
 rations:\nInverted (for transparent samples) and Upright (reflected light 
 configuration\, for opaque samples\, with side\nillumination option). In b
 oth geometries we demonstrate near field Raman enhancement effect due to r
 esonant\ninteraction of light with localized surface plasmon at the apex o
 f a metal AFM probe. Various samples are\nstudied by TERS technique: thin 
 metal oxide layers\, fullerenes\, strained silicon\, carbon nanotubes\, gr
 aphene.\nActual plasmonic and near field nature of the Raman enhancement i
 s proven by a number of ways: dependence\nof the enhancement on the excita
 tion wavelength and polarization\, enhancement versus tip-sample distance\
 ncurves\, observation of selective enhancement of Raman signal from thin s
 urface layers of the sample etc.\nFinally\, the ultimate performance of TE
 RS is demonstrated by measuring Raman 2D maps with subwavelength\nlateral 
 resolution (down to 14 nm) – determined not by the wavelength of light\,
  but by the localization area of\nthe surface plasmon electromagnetic fiel
 d. We discuss current progress in manufacturing reliable TERS probes.
LOCATION:Kapitza Building Seminar Room\, Cavendish Laboratory\, Department
  of Physics
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