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Scattering-type scanning near-field optical microscopy with reconstruction of vertical interaction. Nat Commun 2015; 6:8973. [PMID: 26592949 PMCID: PMC4673874 DOI: 10.1038/ncomms9973] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 10/21/2015] [Indexed: 02/06/2023] Open
Abstract
Scattering-type scanning near-field optical microscopy provides access to super-resolution spectroscopic imaging of the surfaces of a variety of materials and nanostructures. In addition to chemical identification, it enables observations of nano-optical phenomena, such as mid-infrared plasmons in graphene and phonon polaritons in boron nitride. Despite the high lateral spatial resolution, scattering-type near-field optical microscopy is not able to provide characteristics of near-field responses in the vertical dimension, normal to the sample surface. Here, we present an accurate and fast reconstruction method to obtain vertical characteristics of near-field interactions. For its first application, we investigated the bound electromagnetic field component of surface phonon polaritons on the surface of boron nitride nanotubes and found that it decays within 20 nm with a considerable phase change in the near-field signal. The method is expected to provide characterization of the vertical field distribution of a wide range of nano-optical materials and structures. Conventionally, scattering-type scanning near-field optical microscopy does not provide information on the vertical characteristic of near-field responses. Here, Xu et al. develop a method to reconstruct the vertical interaction response between the tip and the sample using this near-field technique.
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52
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Atkin JM, Sass PM, Teichen PE, Eaves JD, Raschke MB. Nanoscale probing of dynamics in local molecular environments. J Phys Chem Lett 2015; 6:4616-4621. [PMID: 26528865 DOI: 10.1021/acs.jpclett.5b02093] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Vibrational spectroscopy can provide information about structure, coupling, and dynamics underlying the properties of complex molecular systems. While measurements of spectral line broadening can probe local chemical environments, the spatial averaging in conventional spectroscopies limits insight into underlying heterogeneity, in particular in disordered molecular solids. Here, using femtosecond infrared scattering scanning near-field optical microscopy (IR s-SNOM), we resolve in vibrational free-induction decay (FID) measurements a high degree of spatial heterogeneity in polytetrafluoroethylene (PTFE) as a dense molecular model system. In nanoscopic probe volumes as small as 10(3) vibrational oscillators, we approach the homogeneous response limit, with extended vibrational dephasing times of several picoseconds, that is, up to 10 times the inhomogeneous lifetime, and spatial average converging to the bulk ensemble response. We simulate the dynamics of relaxation with a finite set of local vibrational transitions subject to random modulations in frequency. The combined results suggest that the observed heterogeneity arises due to static and dynamic variations in the local molecular environment. This approach thus provides real-space and real-time visualization of the subensemble dynamics that define the properties of many functional materials.
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Affiliation(s)
- Joanna M Atkin
- Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States
- Department of Chemistry, University of North Carolina , Chapel Hill, North Carolina 27599, United States
| | - Paul M Sass
- Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States
- Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99354, United States
| | - Paul E Teichen
- Department of Chemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - Joel D Eaves
- Department of Chemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - Markus B Raschke
- Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States
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Khatib O, Wood JD, McLeod AS, Goldflam MD, Wagner M, Damhorst GL, Koepke JC, Doidge GP, Rangarajan A, Bashir R, Pop E, Lyding JW, Thiemens MH, Keilmann F, Basov DN. Graphene-Based Platform for Infrared Near-Field Nanospectroscopy of Water and Biological Materials in an Aqueous Environment. ACS NANO 2015. [PMID: 26223158 DOI: 10.1021/acsnano.5b01184] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Scattering scanning near-field optical microscopy (s-SNOM) has emerged as a powerful nanoscale spectroscopic tool capable of characterizing individual biomacromolecules and molecular materials. However, applications of scattering-based near-field techniques in the infrared (IR) to native biosystems still await a solution of how to implement the required aqueous environment. In this work, we demonstrate an IR-compatible liquid cell architecture that enables near-field imaging and nanospectroscopy by taking advantage of the unique properties of graphene. Large-area graphene acts as an impermeable monolayer barrier that allows for nano-IR inspection of underlying molecular materials in liquid. Here, we use s-SNOM to investigate the tobacco mosaic virus (TMV) in water underneath graphene. We resolve individual virus particles and register the amide I and II bands of TMV at ca. 1520 and 1660 cm(-1), respectively, using nanoscale Fourier transform infrared spectroscopy (nano-FTIR). We verify the presence of water in the graphene liquid cell by identifying a spectral feature associated with water absorption at 1610 cm(-1).
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Affiliation(s)
- Omar Khatib
- Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States
| | - Joshua D Wood
- Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | | | | | | | | | | | | | | | | | - Eric Pop
- Department of Electrical Engineering, Stanford University , Stanford, California 94305, United States
| | | | | | - Fritz Keilmann
- Ludwig-Maximilians-Universität and Center for Nanoscience , 80539 München, Germany
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54
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Kim DS, Kwon H, Nikitin AY, Ahn S, Martín-Moreno L, García-Vidal FJ, Ryu S, Min H, Kim ZH. Stacking Structures of Few-Layer Graphene Revealed by Phase-Sensitive Infrared Nanoscopy. ACS NANO 2015; 9:6765-6773. [PMID: 26050795 DOI: 10.1021/acsnano.5b02813] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The stacking orders in few-layer graphene (FLG) strongly influences the electronic properties of the material. To explore the stacking-specific properties of FLG in detail, one needs powerful microscopy techniques that visualize stacking domains with sufficient spatial resolution. We demonstrate that infrared (IR) scattering scanning near-field optical microscopy (sSNOM) directly maps out the stacking domains of FLG with a nanometric resolution, based on the stacking-specific IR conductivities of FLG. The intensity and phase contrasts of sSNOM are compared with the sSNOM contrast model, which is based on the dipolar tip-sample coupling and the theoretical conductivity spectra of FLG, allowing a clear assignment of each FLG domain as Bernal, rhombohedral, or intermediate stacks for tri-, tetra-, and pentalayer graphene. The method offers 10-100 times better spatial resolution than the far-field Raman and infrared spectroscopic methods, yet it allows far more experimental flexibility than the scanning tunneling microscopy and electron microscopy.
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Affiliation(s)
- Deok-Soo Kim
- †Department of Chemistry, Seoul National University, Seoul 136-701, Korea
| | - Hyuksang Kwon
- †Department of Chemistry, Seoul National University, Seoul 136-701, Korea
| | - Alexey Yu Nikitin
- ‡CIC nanoGUNE Consolider, 20018 Donostia-San Sebastian, Spain
- §IKERBASQUE Basque Foundation for Science, 48011 Bilbao, Spain
| | - Seongjin Ahn
- ∥Department of Physics and Astronomy, Seoul National University, Seoul 446-701, Korea
| | - Luis Martín-Moreno
- ⊥Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, E-50009 Zaragoza, Spain
| | - Francisco J García-Vidal
- #Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Sunmin Ryu
- ∇Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Korea
| | - Hongki Min
- ∥Department of Physics and Astronomy, Seoul National University, Seoul 446-701, Korea
| | - Zee Hwan Kim
- †Department of Chemistry, Seoul National University, Seoul 136-701, Korea
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55
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Tranca DE, Stanciu SG, Hristu R, Stoichita C, Tofail SAM, Stanciu GA. High-resolution quantitative determination of dielectric function by using scattering scanning near-field optical microscopy. Sci Rep 2015; 5:11876. [PMID: 26138665 PMCID: PMC5155613 DOI: 10.1038/srep11876] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 05/28/2015] [Indexed: 12/21/2022] Open
Abstract
A new method for high-resolution quantitative measurement of the dielectric function by using scattering scanning near-field optical microscopy (s-SNOM) is presented. The method is based on a calibration procedure that uses the s-SNOM oscillating dipole model of the probe-sample interaction and quantitative s-SNOM measurements. The nanoscale capabilities of the method have the potential to enable novel applications in various fields such as nano-electronics, nano-photonics, biology or medicine.
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Affiliation(s)
- D. E. Tranca
- Center for Microscopy - Microanalysis and Information Processing, University Politehnica of Bucharest
| | - S. G. Stanciu
- Center for Microscopy - Microanalysis and Information Processing, University Politehnica of Bucharest
| | - R. Hristu
- Center for Microscopy - Microanalysis and Information Processing, University Politehnica of Bucharest
| | - C. Stoichita
- Center for Microscopy - Microanalysis and Information Processing, University Politehnica of Bucharest
| | | | - G. A. Stanciu
- Center for Microscopy - Microanalysis and Information Processing, University Politehnica of Bucharest
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56
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Muller EA, Pollard B, Raschke MB. Infrared Chemical Nano-Imaging: Accessing Structure, Coupling, and Dynamics on Molecular Length Scales. J Phys Chem Lett 2015; 6:1275-84. [PMID: 26262987 DOI: 10.1021/acs.jpclett.5b00108] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
This Perspective highlights recent advances in infrared vibrational chemical nano-imaging. In its implementations of scattering scanning near-field optical microscopy (s-SNOM) and photothermal-induced resonance (PTIR), IR nanospectroscopy provides few-nanometer spatial resolution for the investigation of polymer, biomaterial, and related soft-matter surfaces and nanostructures. Broad-band IR s-SNOM with coherent laser and synchrotron sources allows for chemical recognition with small-ensemble sensitivity and the potential for sensitivity reaching the single-molecule limit. Probing selected vibrational marker resonances, it gives access to nanoscale chemical imaging of composition, domain morphologies, order/disorder, molecular orientation, or crystallographic phases. Local intra- and intermolecular coupling can be measured through frequency shifts of a vibrational marker in heterogeneous environments and associated inhomogeneities in vibrational dephasing. In combination with ultrafast spectroscopy, the vibrational coherent evolution of homogeneous sub-ensembles coupled to their environment can be observed. Outstanding challenges are discussed in terms of extensions to coherent and multidimensional spectroscopies, implementation in liquid and in situ environments, general sample limitations, and engineering s-SNOM scanning probes to better control the nano-localized optical excitation and to increase sensitivity.
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Affiliation(s)
- Eric A Muller
- Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, United States
| | - Benjamin Pollard
- Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, United States
| | - Markus B Raschke
- Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, United States
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57
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Centrone A. Infrared Imaging and Spectroscopy Beyond the Diffraction Limit. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2015; 8:101-26. [PMID: 26001952 DOI: 10.1146/annurev-anchem-071114-040435] [Citation(s) in RCA: 159] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Progress in nanotechnology is enabled by and dependent on the availability of measurement methods with spatial resolution commensurate with nanomaterials' length scales. Chemical imaging techniques, such as scattering scanning near-field optical microscopy (s-SNOM) and photothermal-induced resonance (PTIR), have provided scientists with means of extracting rich chemical and structural information with nanoscale resolution. This review presents some basics of infrared spectroscopy and microscopy, followed by detailed descriptions of s-SNOM and PTIR working principles. Nanoscale spectra are compared with far-field macroscale spectra, which are widely used for chemical identification. Selected examples illustrate either technical aspects of the measurements or applications in materials science. Central to this review is the ability to record nanoscale infrared spectra because, although chemical maps enable immediate visualization, the spectra provide information to interpret the images and characterize the sample. The growing breadth of nanomaterials and biological applications suggest rapid growth for this field.
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Affiliation(s)
- Andrea Centrone
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899;
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59
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Gerber JA, Berweger S, O'Callahan BT, Raschke MB. Phase-resolved surface plasmon interferometry of graphene. PHYSICAL REVIEW LETTERS 2014; 113:055502. [PMID: 25126927 DOI: 10.1103/physrevlett.113.055502] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Indexed: 05/15/2023]
Abstract
The surface plasmon polaritons (SPPs) of graphene reflect the microscopic spatial variations of underlying electronic structure and dynamics. Here, we excite and image the graphene SPP response in phase and amplitude by near-field interferometry. We develop an analytic cavity model that can self-consistently describe the SPP response function for edge, grain boundary, and defect SPP reflection and scattering. The derived SPP wave vector, damping, and carrier mobility agree with the results from more complex models. Spatial variations in the Fermi level and associated variations in dopant concentration reveal a nanoscale spatial inhomogeneity in the reduced conductivity at internal boundaries. The additional SPP phase information thus opens a new degree of freedom for spatial and spectral graphene SPP tuning and modulation for optoelectronics applications.
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Affiliation(s)
- Justin A Gerber
- Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, USA
| | - Samuel Berweger
- Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, USA
| | - Brian T O'Callahan
- Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, USA
| | - Markus B Raschke
- Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, USA
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60
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Govyadinov AA, Mastel S, Golmar F, Chuvilin A, Carney PS, Hillenbrand R. Recovery of permittivity and depth from near-field data as a step toward infrared nanotomography. ACS NANO 2014; 8:6911-21. [PMID: 24897380 DOI: 10.1021/nn5016314] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The increasing complexity of composite materials structured on the nanometer scale requires highly sensitive analytical tools for nanoscale chemical identification, ideally in three dimensions. While infrared near-field microscopy provides high chemical sensitivity and nanoscopic spatial resolution in two dimensions, the quantitative extraction of material properties of three-dimensionally structured samples has not been achieved yet. Here we introduce a method to perform rapid recovery of the thickness and permittivity of simple 3D structures (such as thin films and nanostructures) from near-field measurements, and provide its first experimental demonstration. This is accomplished via a novel nonlinear invertible model of the imaging process, taking advantage of the near-field data recorded at multiple harmonics of the oscillation frequency of the near-field probe. Our work enables quantitative nanoscale-resolved optical studies of thin films, coatings, and functionalization layers, as well as the structural analysis of multiphase materials, among others. It represents a major step toward the further goal of near-field nanotomography.
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Abstract
Characterizing and ultimately controlling the heterogeneity underlying biomolecular functions, quantum behavior of complex matter, photonic materials, or catalysis requires large-scale spectroscopic imaging with simultaneous specificity to structure, phase, and chemical composition at nanometer spatial resolution. However, as with any ultrahigh spatial resolution microscopy technique, the associated demand for an increase in both spatial and spectral bandwidth often leads to a decrease in desired sensitivity. We overcome this limitation in infrared vibrational scattering-scanning probe near-field optical microscopy using synchrotron midinfrared radiation. Tip-enhanced localized light-matter interaction is induced by low-noise, broadband, and spatially coherent synchrotron light of high spectral irradiance, and the near-field signal is sensitively detected using heterodyne interferometric amplification. We achieve sub-40-nm spatially resolved, molecular, and phonon vibrational spectroscopic imaging, with rapid spectral acquisition, spanning the full midinfrared (700-5,000 cm(-1)) with few cm(-1) spectral resolution. We demonstrate the performance of synchrotron infrared nanospectroscopy on semiconductor, biomineral, and protein nanostructures, providing vibrational chemical imaging with subzeptomole sensitivity.
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62
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Ultrastable atomic force microscopy: improved force and positional stability. FEBS Lett 2014; 588:3621-30. [PMID: 24801176 DOI: 10.1016/j.febslet.2014.04.033] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 04/18/2014] [Accepted: 04/23/2014] [Indexed: 11/20/2022]
Abstract
Atomic force microscopy (AFM) is an exciting technique for biophysical studies of single molecules, but its usefulness is limited by instrumental drift. We dramatically reduced positional drift by adding two lasers to track and thereby actively stabilize the tip and the surface. These lasers also enabled label-free optical images that were spatially aligned to the tip position. Finally, sub-pN force stability over 100 s was achieved by removing the gold coating from soft cantilevers. These enhancements to AFM instrumentation can immediately benefit research in biophysics and nanoscience.
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