Infrared-spectroscopic nanoimaging with a thermal source.

Fourier-transform infrared (FTIR) spectroscopy is a widely used analytical tool for chemical identification of inorganic, organic and biomedical materials, as well as for exploring conduction phenomena. Because of the diffraction limit, however, conventional FTIR cannot be applied for nanoscale imaging. Here we demonstrate a novel FTIR system that allows for infrared-spectroscopic nanoimaging of dielectric properties (nano-FTIR). Based on superfocusing of thermal radiation with an infrared antenna, detection of the scattered light, and strong signal enhancement employing an asymmetric FTIR spectrometer, we improve the spatial resolution of conventional infrared spectroscopy by more than two orders of magnitude. By mapping a semiconductor device, we demonstrate spectroscopic identification of silicon oxides and quantification of the free-carrier concentration in doped Si regions with a spatial resolution better than 100  nm. We envisage nano-FTIR becoming a powerful tool for chemical identification of nanomaterials, as well as for quantitative and contact-free measurement of the local free-carrier concentration and mobility in doped nanostructures.

[1]  Gerhard Schwaab,et al.  Setup of a scanning near field infrared microscope (SNIM): imaging of sub-surface nano-structures in gallium-doped silicon. , 2006, Physical chemistry chemical physics : PCCP.

[2]  Thomas Taubner,et al.  Infrared spectroscopic mapping of single nanoparticles and viruses at nanoscale resolution. , 2006, Nano letters.

[3]  E. Bakkers,et al.  Nanoscale free-carrier profiling of individual semiconductor nanowires by infrared near-field nanoscopy. , 2010, Nano letters.

[4]  F. Keilmann,et al.  Simultaneous IR Material Recognition and Conductivity Mapping by Nanoscale Near‐Field Microscopy , 2007 .

[5]  F. Lederer,et al.  Amplitude- and phase-resolved optical near fields of split-ring-resonator-based metamaterials. , 2008, Optics letters.

[6]  P. Griffiths.  Fourier Transform Infrared Spectrometry , 2007 .

[7]  F. Keilmann,et al.  Complex optical constants on a subwavelength scale. , 2000, Physical review letters.

[8]  Lukas Novotny,et al.  Principles of Nano-Optics by Lukas Novotny , 2006 .

[9]  A. Boccara,et al.  Near-field optical microscope based on local perturbation of a diffraction spot. , 1995, Optics letters.

[10]  F. Keilmann,et al.  Broadband-infrared assessment of phonon resonance in scattering-type near-field microscopy , 2011 .

[11]  Y. Martin,et al.  Scanning Interferometric Apertureless Microscopy: Optical Imaging at 10 Angstrom Resolution , 1995, Science.

[12]  F. Keilmann,et al.  Near-field probing of vibrational absorption for chemical microscopy , 1999, Nature.

[13]  Klaus Gerwert,et al.  Functional waters in intraprotein proton transfer monitored by FTIR difference spectroscopy , 2006, Nature.

[14]  R. Hillenbrand,et al.  Analytical model for quantitative prediction of material contrasts in scattering-type near-field optical microscopy. , 2007, Optics express.

[15]  Satoshi Kawata,et al.  Scanning probe optical microscopy using a metallic probe tip , 1995 .

[16]  F. Keilmann,et al.  Spectroscopic near-field microscopy using frequency combs in the mid-infrared. , 2006, Optics express.

[17]  G. Masetti,et al.  Modeling of carrier mobility against carrier concentration in arsenic-, phosphorus-, and boron-doped silicon , 1983, IEEE Transactions on Electron Devices.

[18]  B. Hecht,et al.  Principles of nano-optics , 2006 .

[19]  F. Keilmann.  Vibrational-infrared near-field microscopy , 2002 .

[20]  F. Keilmann,et al.  Nanoscale polymer recognition by spectral signature in scattering infrared near-field microscopy , 2004 .

[21]  Jean-Jacques Greffet,et al.  Thermal radiation scanning tunnelling microscopy , 2006, Nature.

[22]  R. Hillenbrand,et al.  Infrared nanoscopy of strained semiconductors. , 2009, Nature nanotechnology.

[23]  F. Keilmann,et al.  Antenna-mediated back-scattering efficiency in infrared near-field microscopy. , 2008, Optics express.

[24]  A. Zayats,et al.  Nano-optics and near-field optical microscopy , 2009 .

[25]  Ely E. Bell,et al.  Measurement of the optical constants of crystal quartz in the far infrared with the asymmetric Fourier-transform method , 1967 .

[26]  S Winnerl,et al.  Anisotropy contrast in phonon-enhanced apertureless near-field microscopy using a free-electron laser. , 2008, Physical review letters.

[27]  W. Cai,et al.  Plasmonics for extreme light concentration and manipulation. , 2010, Nature materials.

[28]  Joachim A. Hering,et al.  Fourier transform infrared. , 2005 .

[29]  M. Gunde.  Vibrational modes in amorphous silicon dioxide , 2000 .

[30]  F. Keilmann,et al.  Phonon-enhanced light–matter interaction at the nanometre scale , 2002, Nature.

[31]  J. Aizpurua,et al.  Infrared imaging of single nanoparticles via strong field enhancement in a scanning nanogap. , 2006, Physical review letters.

[32]  Dong Ha Kim,et al.  Apertureless near-field vibrational imaging of block-copolymer nanostructures with ultrahigh spatial resolution. , 2005, Chemphyschem : a European journal of chemical physics and physical chemistry.

[33]  R. Hillenbrand,et al.  Infrared spectroscopic near-field mapping of single nanotransistors , 2010, Nanotechnology.

[34]  Gilbert C. Walker,et al.  Apertureless Scanning Near-Field Infrared Microscopy of a Rough Polymeric Surface , 2001 .

[35]  P. Kim,et al.  Dirac charge dynamics in graphene by infrared spectroscopy , 2008, 0807.3780.

[36]  M. Allegrini,et al.  Artifact-free near-field optical imaging by apertureless microscopy , 2000 .