Scanning near-field optical microscopy by near-field reflectance enhancement: a versatile and valid technique

Kaupp, Gerd; Herrmann, Andreas

doi:10.1002/(sici)1099-1395(199902)12:2<141::aid-poc101>3.0.co;2-n

Cited by 5 publications

(3 citation statements)

References 12 publications

(5 reference statements)

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“…A SNOM DME Rasterscope 4000 in a reflection-back-to-fiber configuration was used to acquire topographical and optical information on the particle films surface. In this configuration, an uncoated optical fiber tip is used to simultaneously illuminate and detect the evanescent field generated at the sample surface. − Tapered optical fiber probes suitable for SNOM imaging were produced through a multistage heating-pulling process using a programmable micropipet puller P-2000 (Sutter Instruments). Examination of the obtained tips in a field-emission gun scanning electron microscope indicates tip curvature radii of 13.3 nm and cone angle of 5.8°.…”

Section: Methodsmentioning

confidence: 99%

“…An argon-ion laser (488 nm) coupled into the fiber was used to illuminate the sample. The near-field enhanced [33][34][35] reflected light was detected through a cross-polarized detection setup in order to remove stray light and to record the chemical contrast of the sample surface. The tip-to-sample shear-force gap was kept constant while scanning.…”

Section: Scanning Near Field Optical Microscopy (Snom)mentioning

confidence: 99%

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Latex Particle Heterogeneity and Clustering in Films

2003

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A poly(styrene-co-acrylamide) (PS-AAM) latex was prepared by emulsion polymerization and purified by sedimentation of colloidal crystals. These were diluted and dried on a mica substrate forming submonolayers that were examined by atomic force microscopy (AFM), scanning electron microscopy (SEM), and near-field optical microscopy (SNOM). The images show domains of at least two particle types clustered within the films, in every field examined. Zonal centrifugation of the colloidal-crystal forming particles still produced three separated fractions, two of which were further cast into uniform submonolayers. These results show that latex particles have a strong tendency to cluster with identical particles even in the presence of other, similar particles. However, colloidal crystal formation has a limited tolerance to particle heterogeneity but the quality of the dry macrocrystals is strongly dependent on particle uniformity.

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Section: Methodsmentioning

confidence: 99%

Section: Scanning Near Field Optical Microscopy (Snom)mentioning

confidence: 99%

Latex Particle Heterogeneity and Clustering in Films

2003

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“…Unlike aperture SNOM [2] and apertureless scattering SNOM in tapping mode [3], only this apertureless technique is adapted to "real world" transparent and opaque samples. Our basic new and unexpected physical effect, which allows for the very good resolution despite an illuminated area of about 1 μm diameter, is the strongly enhanced reflection back into the very sharp fiber at shear-force distance [4,5]. An illuminated tip with very sharp apex (end radius 10-20 nm) must be used.…”

Section: Introductionmentioning

confidence: 99%

Scanning near‐field optical microscopy on rough surfaces: Applications in chemistry, biology, and medicine

Kaupp

2006

International Journal of Photoenergy

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Shear-force apertureless scanning near-field optical microscopy (SNOM) with very sharp uncoated tapered waveguides relies on the unexpected enhancement of reflection in the shear-force gap. It is the technique for obtaining chemical (materials) contrast in the optical image of “real world” surfaces that are rough and very rough without topographical artifacts, and it is by far less complicated than other SNOM techniques that can only be used for very flat surfaces. The experimental use of the new photophysical effect is described. The applications of the new technique are manifold. Important mechanistic questions in solid-state chemistry (oxidation, diazotization, photodimerization, surface hydration, hydrolysis) are answered with respect to simultaneous AFM (atomic force microscopy) and detailed crystal packing. Prehistoric petrified bacteria and concomitant pyrite inclusions are also investigated with local RAMAN SNOM. Polymer beads and unstained biological objects (rabbit heart, shrimp eye) allow for nanoscopic analysis of cell organelles. Similarly, human teeth and a cancerous tissue are analyzed. Bladder cancer tissue is clearly differentiated from healthy tissue without staining and this opens a new highly promising diagnostic tool for precancer diagnosis. Industrial applications are demonstrated at the corrosion behavior of dental alloys (withdrawal of a widely used alloy, harmless substitutes), improvement of paper glazing, behavior of blood bags upon storage, quality assessment of metal particle preparations for surface enhanced RAMAN spectroscopy, and determination of diffusion coefficient and light fastness in textile fiber dyeing. The latter applications include fluorescence SNOM. Local fluorescence SNOM is also used in the study of partly aggregating dye nanoparticles within resin/varnish preparations. Unexpected new insights are obtained in all of the various fields that cannot be obtained by other techniques.

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Artifacts in scanning near-field optical microscopy (SNOM) due to deficient tips

Kaupp

Herrmann

Haak

1999

J. Phys. Org. Chem.

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Apertureless scanning near-field optical microscopy (SNOM) in the reflection-back-to-the-fiber configuration is possible on rough surfaces of practical importance and reaches 15 nm lateral resolution. The feedback for constant distance mode is provided by shear-force atomic force microscopy. Any artifacts in the atomic force microscopy will translate into artificial optical responses. Very sharp tapered tips (radius ca. 15 nm, apex angle`10°) are required. Only these give the strongly enhanced reflectance in shear-force distance, do not break as easily as do more blunt tips, and can follow the topography in order to provide chemical SNOM contrast without topographic errors. In the absence of significant reflectance enhancement, if blunt or abrased or broken tips are used, not SNOM but artificial 'optical contrast' is recorded. Metal-coated tips are unsuitable: they become hot, give poor resolution and are the source of numerous additional artifacts that are summarized for comparison. The SNOM artifacts are subdivided into:* topographic errors-if chemical uniform topography does give some optical response; * lack of spatial correlation-if the optical signal does not reproduce the site of the emitter or of the chemical contrast; * tip imaging-very large features and more or less negative differentials therefrom; * contrast inversion-false sign of optical contrast; * split optical contrast-signal is split into two unequal parts with the same (false) sign of the contrast; * artificial stripes-instead of chemical/emissive contrast artificial stripes, that are not always 'interference fringes' or 'edge-contrast'.The artifacts can be easily recognized in published images from different techniques and modes of SNOM. Their analysis would be facilitated if full x/y/z data were published instead of two-dimensional images. We therefore disclose interactively analyzable VRML data in the EPOC version.

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Scanning near-field optical microscopy by near-field reflectance enhancement: a versatile and valid technique

Cited by 5 publications

References 12 publications

Latex Particle Heterogeneity and Clustering in Films

Latex Particle Heterogeneity and Clustering in Films

Scanning near‐field optical microscopy on rough surfaces: Applications in chemistry, biology, and medicine

Artifacts in scanning near-field optical microscopy (SNOM) due to deficient tips

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