Infrared near-field spectroscopy of trace explosives using an external cavity quantum cascade laser

Craig, Ian M.; Taubman, Matthew S.; Lea, Alan S.; Phillips, Mark C.; Josberger, Erik E.; Raschke, Markus B.

doi:10.1364/oe.21.030401

Cited by 29 publications

(18 citation statements)

References 49 publications

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“…Various radiation sources have been evaluated during the last years for near-field IR spectroscopy. This includes tunable gas lasers with a rather limited accessible spectral range, thermal sources [37,38], quantum cascade lasers [39], and synchrotron radiation [40,41]. Successful nano-FTIR measurements using synchrotron radiation were recently demonstrated on partially Au-coated SiC samples [42].…”

Section: Introductionmentioning

confidence: 99%

Characterization of semiconductor materials using synchrotron radiation-based near-field infrared microscopy and nano-FTIR spectroscopy

Hermann¹,

Hoehl²,

Ulrich³

et al. 2014

Opt. Express

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Abstract:We describe the application of scattering-type near-field optical microscopy to characterize various semiconducting materials using the electron storage ring Metrology Light Source (MLS) as a broadband synchrotron radiation source. For verifying high-resolution imaging and nano-FTIR spectroscopy we performed scans across nanoscale Si-based surface structures. The obtained results demonstrate that a spatial resolution below 40 nm can be achieved, despite the use of a radiation source with an extremely broad emission spectrum. This approach allows not only for the collection of optical information but also enables the acquisition of nearfield spectral data in the mid-infrared range. The high sensitivity for spectroscopic material discrimination using synchrotron radiation is presented by recording near-field spectra from thin films composed of different materials used in semiconductor technology, such as SiO 2 , SiC, Si x N y , and TiO 2 . ©2014 Optical Society of AmericaOCIS codes: (120.0120) Instrumentation, measurement, and metrology; (180.4243) Near-field microscopy; (240.0240) Optics at surfaces; (300.0300) Spectroscopy; (310.6860) Thin films, optical properties. 1248-1262 (2014). 5. S. Kawata and Y. Inouye, "Scanning probe optical microscopy using a metallic probe tip," Ultramicroscopy 57(2-3), 313-317 (1995). 6. F. Zenhausern, Y. Martin, and H. K. Wickramasinghe, "Scanning interferometric apertureless microscopy: References and linksOptical imaging at 10 angstrom resolution," Science 269(5227), 1083-1085 (1995). 7. R. Bachelot, P. Gleyzes, and A. C. Boccara, "Near-field optical microscope based on local perturbation of a diffraction spot," Opt. Lett. 20(18), 1924-1926 (1995). 8. B. Knoll and F. Keilmann, "Near-field probing of vibrational absorption for chemical microscopy," Nature 399(6732), 134-137 (1999 Helm, "Anisotropy contrast in phonon-enhanced apertureless near-field microscopy using a free-electron laser," Phys. Rev. Lett.

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Section: Introductionmentioning

confidence: 99%

Characterization of semiconductor materials using synchrotron radiation-based near-field infrared microscopy and nano-FTIR spectroscopy

Hermann¹,

Hoehl²,

Ulrich³

et al. 2014

Opt. Express

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“…This measurement procedure can be time-consuming and spectra can be easily affected by changing experimental conditions like tip degradation during scanning [4]. For fastly tunable narrow-band lasers like quantum cascade lasers (QCLs) also used for SNOM [21,22], it is possible to circumvent these issues by automatically changing the wavelength while measuring at a single position on the sample [21]. However, the use of QCLs is limited in terms of the accessible spectral range.…”

Section: Introductionmentioning

confidence: 99%

Near-field imaging and spectroscopy of locally strained GaN using an IR broadband laser

et al. 2014

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Scattering-type scanning near-field optical microscopy (SNOM) offers the possibility to analyze material properties like strain in crystals at the nanoscale. In this paper we introduce a SNOM setup employing a newly developed tunable broadband laser source with a covered spectral range from 9 µm to 16 µm. This setup allows for the first time optical analyses of the crystal structure of gallium nitride (GaN) at the nanometer scale by excitation of a near-field phonon resonance around 14.5 µm. On the example of an artificially induced stress field within a GaN wafer, we present a method for a 2D visualization of small deviations in the crystal structure, which allows for fast qualitative characterizations. Subsequently, the stress levels at chosen points were quantified by recording complex near-field spectra and correlating them with theoretical model calculations. Applied to the cross-section of a heteroepitaxially grown GaN wafer, we finally demonstrate the capability of our setup to analyze the relaxation of the crystal structure along the growth axis with a nanometer spatial resolution.

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“…www.annualreviews.org • Infrared Imaging and Spectroscopy 5.7 Changes may still occur before final publication online and in print Quantum cascade lasers have wider wavelength tunability (a few hundred wavenumbers) than CO 2 lasers, enabling the acquisition of near-field IR maps and spectra (31)(32)(33)63). Even broader spectral coverage in s-SNOM was achieved using a thermal source, similar to those used in FTIR (98), but the low brilliance of this source limits its applicability.…”

Section: Scattering Scanning Near-field Optical Microscopymentioning

confidence: 99%

“…Although s-SNOM technology benefits from 30 years of steady development, in the author's opinion, it became of general utility to the analytical chemist only recently, thanks to the ability of recording nanoscale IR spectra. Such an advance has been enabled primarily by the availability of continuous narrow-band lasers with broader wavelength tunability (31)(32)(33) and by broadband sources with wider bandwidth (34)(35)(36)(37)(38)(39). By comparison, PTIR (28)(29)(30) couples a pulsed, wavelength-tunable laser and an AFM cantilever to measure light absorption in the sample by transducing the sample thermal expansion into mechanical cantilever motion.…”

Section: Introductionmentioning

confidence: 99%

Infrared Imaging and Spectroscopy Beyond the Diffraction Limit

Centrone

2015

Annual Rev. Anal. Chem.

243

275

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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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Infrared near-field spectroscopy of trace explosives using an external cavity quantum cascade laser

Cited by 29 publications

References 49 publications

Characterization of semiconductor materials using synchrotron radiation-based near-field infrared microscopy and nano-FTIR spectroscopy

Characterization of semiconductor materials using synchrotron radiation-based near-field infrared microscopy and nano-FTIR spectroscopy

Near-field imaging and spectroscopy of locally strained GaN using an IR broadband laser

Infrared Imaging and Spectroscopy Beyond the Diffraction Limit

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