Locally resolved infrared spectroscopy

Piednoir, Agnès; Creuzet, F.; Licoppe, Christian; Ortéga, J.M.

doi:10.1016/0304-3991(94)00153-e

Cited by 22 publications

(10 citation statements)

References 2 publications

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“…Research advances in near-field optics have been numerous and exciting in the visible range, and in recent years were extended into the IR. [6][7][8][9][10][11][12][13][14][15][16][17] Although there is some very good work in IR, there are still significant challenges. The main issues are associated with the lack of broadly tunable IR sources and challenges associated with obtaining interpretable spectra.…”

Section: Introductionmentioning

confidence: 99%

AFM–IR: Combining Atomic Force Microscopy and Infrared Spectroscopy for Nanoscale Chemical Characterization

Dazzi

Prater²,

Hu³

et al. 2012

Appl Spectrosc

463

444

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Polymer and life science applications of a technique that combines atomic force microscopy (AFM) and infrared (IR) spectroscopy to obtain nanoscale IR spectra and images are reviewed. The AFM–IR spectra generated from this technique contain the same information with respect to molecular structure as conventional IR spectroscopy measurements, allowing significant leverage of existing expertise in IR spectroscopy. The AFM–IR technique can be used to acquire IR absorption spectra and absorption images with spatial resolution on the 50 to 100 nm scale, versus the scale of many micrometers or more for conventional IR spectroscopy. In the life sciences, experiments have demonstrated the capacity to perform chemical spectroscopy at the sub-cellular level. Specifically, the AFM–IR technique provides a label-free method for mapping IR-absorbing species in biological materials. On the polymer side, AFM–IR was used to map the IR absorption properties of polymer blends, multilayer films, thin films for active devices such as organic photovoltaics, microdomains in a semicrystalline polyhydroxyalkanoate copolymer, as well as model pharmaceutical blend systems. The ability to obtain spatially resolved IR spectra as well as high-resolution chemical images collected at specific IR wavenumbers was demonstrated. Complementary measurements mapping variations in sample stiffness were also obtained by tracking changes in the cantilever contact resonance frequency. Finally, it was shown that by taking advantage of the ability to arbitrarily control the polarization direction of the IR excitation laser, it is possible to obtain important information regarding molecular orientation in electrospun nanofibers.

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Section: Introductionmentioning

confidence: 99%

AFM–IR: Combining Atomic Force Microscopy and Infrared Spectroscopy for Nanoscale Chemical Characterization

Dazzi

Prater²,

Hu³

et al. 2012

Appl Spectrosc

463

444

View full text Add to dashboard Cite

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“…131 As in all near-field interactions, the optical near-field signals are strongly dependent on the distance. Typical measurement distances for SNOM in the infrared region are 0.2 -5 µm, 16,119 for SNOM with visual wavelengths below 10 nm. 132 There are different concepts for distance control: glass fibers with conductive coatings can use photon tunneling; in other SNOM techniques control is effected by shearing forces on the tip 133 or by capacity.…”

Section: Microwaves and Lightmentioning

confidence: 99%

“…132 There are different concepts for distance control: glass fibers with conductive coatings can use photon tunneling; in other SNOM techniques control is effected by shearing forces on the tip 133 or by capacity. 119,134 The resolution is limited by the aperture and measuring distance. By reducing the measuring distance to 2 -5 nm the resolution could be improved from about 700 to 25 nm.…”

Section: Microwaves and Lightmentioning

confidence: 99%

Microscopy of Coatings

Rädlein¹

2000

Encyclopedia of Analytical Chemistry

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Fundamental research on films and the development and optimization of coatings are not possible without high‐resolution imaging. This article describes the advantages and disadvantages of the newly introduced scanning probe microscopy (SPM) in comparison with well‐established microscopy techniques with light and particles [e.g. scanning electron microscopy (SEM) and transmission electron microscopy (TEM)], which are limited by the diffraction limit, i.e. 200 nm for conventional light microscopy and 4 nm for SEM. This limit does not hold for SPM, which uses near‐field interactions for imaging. Thus, even simple atoms or molecules can be resolved on well‐ordered structures by scanning tunneling microscopy (STM) or atomic force microscopy (AFM). Both possess an extremely good height sensitivity of 0.02 nm. 1 In the constant‐height operation mode, AFM can detect vertical forces as low as 10 −15 –10 −4 N. Atomic resolution is not always possible or not always necessary for many practical applications; a lateral resolution of a few nanometers is sufficient. Besides the capability of achieving this value with ease, simple sample preparation, versatile environmental conditions and observation of reactions in situ are advantages of STM and AFM. Especially AFM has proved to be a useful technique for investigating coatings, because it is independent of conductivity and provides topographic data together with information on structure, local variations of mechanical properties and surface alterations in different media. However, some artifacts and restrictions have to be considered which can differ considerably from customary electron micrographs with comparable resolutions, such as onset overswing and tip convolution. Microscopy helps in solving coating problems according to substrate quality, nucleation, wettability, thickness, roughness, microstructure, crystal phases (texture, orientation), lateral and vertical homogeneity, density, porosity, interfaces, adhesion, hardness, stress, scratch and abrasion resistance, tribology, wear and corrosion. Practical examples of microscopy results on these questions are presented together with suitable preparation methods and interpretation of artifacts.

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“…However, due to the lack of powerful infrared tunable lasers this had not been done until now in the infrared spectral range. At CLIO, a group coming from the St-Gobain-CNRS laboratory has undertaken such a project [39], which is now developed locally.…”

Section: Near-field Microscopymentioning

confidence: 99%

Free-electron lasers sources for scientific applications

Couprie

Ortéga

2000

Analusis

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The free-electron laser (FEL), operated for the first time in 1978 [1] is based on the amplification of an optical wave by a high-energy electron beam. After about 20 years of research, it appears that the FEL is mature in the spectral range of UV to infrared, although intensive research is continuing in the field of short wavelength and high power [2].The gain medium of a FEL is a high-energy electron beam (several MeV or more) passing through a transverse magnetic field called "undulator". The undulator causes an electron oscillation perpendicular to its direction of propagation and, therefore, couples it with the optical field. Undulators are also commonly used on storage rings as powerful UV and X ray sources [3]. The relative degree of coherence of the light produced by these sources is due to the periodicity of the undulator providing a higher spectral brilliance than ordinary synchrotron radiation. In addition, under certain conditions, the interaction in the undulator of the emitted radiation with the electron beam leads to light amplification [2]. This effect, when operating within an optical cavity ( Fig. 1), is the principle of the Free-Electron Laser ("FEL").The laser radiation is emitted by the FEL at the "resonance wavelength" λ R :λ o is the magnetic period of the undulator (a few cm in practice); E = γmc 2 is the electron beam energy (Einstein's formula) giving numerically for the relativistic factor: γ ≅ 2.E(MeV); K = eBλ o /2πmc is the deflection parameter proportional to the magnetic field B of the undulator (K = 1 to 3 typically).Tuning of the laser wavelength is done continuously by varying either the undulator gap, which modifies the value of the K parameter, the electron energy or a combination of the two.Typical electron energies are:-5 -10 MeV to produce wavelengths in far infrared -10 -50 MeV mid-infrared -500 -1000 MeV UV -VUV -10 to 20 GeV? X raysThe length of an accelerator is about 1 m/5 MeV, except for electrostatic machines which are longer, but limited to a few MeV.Indeed, the most striking characteristic of the FEL is that the gain medium can be tuned to any wavelength. The lasing range is limited, in principle, only by the energies that can be reached by the accelerator, while attaining sufficiently good beam properties. However, at short wavelength, it is very difficult to obtain a sufficiently high optical gain.In the infrared spectral range, the combination of high achievable gains and broadband metal mirrors leads to continuously tuning FELs over a very wide spectral range (1 or 2 orders of magnitude in wavelength). In the UV & VUV, the reflectivity achievable with mirrors with today technology decrease rapidly at wavelengths shorter than about 200 nm. Therefore, the shortest lasing wavelength is presently about 200 nm [4] and nowadays 5 FELs are operating at 300 nm or below. Coherent emission in the VUV range has been obtained by harmonic generation of an external laser focused on the electron beam [5]. In the future, short wavelength harmonics of the FEL itself could con...

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Locally resolved infrared spectroscopy

Cited by 22 publications

References 2 publications

AFM–IR: Combining Atomic Force Microscopy and Infrared Spectroscopy for Nanoscale Chemical Characterization

AFM–IR: Combining Atomic Force Microscopy and Infrared Spectroscopy for Nanoscale Chemical Characterization

Microscopy of Coatings

Free-electron lasers sources for scientific applications

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