Transmission near-field scanning microscope for infrared chemical imaging

Dragnea, Bogdan; Preusser, Jan; Schade, Wolfgang; Leone, Stephen R.; Hinsberg, William D.

doi:10.1063/1.371127

Cited by 34 publications

(40 citation statements)

References 17 publications

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“…While the use of a free electron laser source limits applications to the relatively few researchers who can access such a device, in principle the general technique could be applied to alternative tunable IR laser sources. Recently interesting IR-SNOM measurements have been done using a color center laser pumped by a Kr + laser [18,19]. We use the shear force feedback mechanism to control the tip-to-surface distance.…”

Section: Methodsmentioning

confidence: 99%

Spectroscopic infrared scanning near-field optical microscopy (IR-SNOM)

Vobornik

Margaritondo

Sanghera

et al. 2005

Journal of Alloys and Compounds

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Scanning near-field optical microscopy (SNOM or NSOM) is the technique with the highest lateral optical resolution available today, while infrared (IR) spectroscopy has a high chemical specificity. Combining SNOM with a tunable IR source produces a unique tool, IR-SNOM, capable of imaging distributions of chemical species with a 100 nm spatial resolution. We present in this paper boron nitride (BN) thin film images, where IR-SNOM shows the distribution of hexagonal and cubic phases within the sample. Exciting potential applications in biophysics and medical sciences are illustrated with SNOM images of the distribution of different chemical species within cells. We present in this article images with resolutions of the order of λ/60 with SNOM working with infrared light. With our SNOM setup, we routinely get optical resolutions between 50 and 150 nm, regardless of the wavelength of the light used to illuminate the sample.

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Section: Methodsmentioning

confidence: 99%

Spectroscopic infrared scanning near-field optical microscopy (IR-SNOM)

Vobornik

Margaritondo

Sanghera

et al. 2005

Journal of Alloys and Compounds

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“…Although this issue has attracted growing attention in recent years, [16][17][18] the mechanisms of image formation are not yet well understood, and different contrast parameters have been claimed by various researchers using similar techniques. 13,15 In the present work we study the contrast parameters in transmission mode ͑fiber-based͒ near-field microscopy, including the influence of the sample and substrate refraction indices, as well as the role of sample topography in near-field image formation.…”

Section: Introductionmentioning

confidence: 99%

On contrast parameters and topographic artifacts in near-field infrared microscopy

Palanker

Simanovskii

Huie

et al. 2000

Journal of Applied Physics

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Near-field microscopy overcomes the diffraction limit through the partial conversion of the evanescent fields, formed around the subwavelength sources of light, into propagating waves by interactions between the probe and the sample. Contrast parameters in this imaging technique are quite different from those in conventional ͑far-field͒ optics. We study the mechanisms of image formation in the transmission mode of a near-field microscope in the mid-infrared part of the spectrum ͑6-10 m͒. The amount of light propagating from a subwavelength aperture through a flat substrate ͑''allowed'' light͒ is found to strongly increase as the tip approaches the sample, generating topographic artifacts in near-field images. Such artifacts can be eliminated by flat sample preparation techniques. The transmitted power is strongly influenced by the refraction index of the sample resulting in a substantial difference of the near-field spectrum from the far-field one. A model describing tunneling of light through a subwavelength aperture into the substrate has been developed and is in very good agreement with the experimental data. The model predicts that spectral sensitivity is enhanced with smaller tip diameters.

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“…Therefore, special techniques must be applied to create a low aspect ratio taper. Multiple step processes such as variable-pulling rates, 16 or combinations of selective etching, pulling, and focused ion beam milling, 17,18 all aim to produce a multiple taper structure, which improves the throughput by orders of magnitude with respect to singletaper fibers. In the present work fiber tips obtained by the variable-pulling method were used.…”

Section: A Infrared Fiber Tipsmentioning

confidence: 99%

“…16 The tips were fabricated from fluoride glass fibers, transparent between 0.45 and 5.0 m. They resemble a steeple-on-a-mesa, with a 200-300 nm aperture obtained by lateral coating with 120 nm thick Al by thermal evaporation in a custom-built vacuum chamber with a base pressure of ϳ10 Ϫ6 Torr (7.5 ϫ10 Ϫ3 Pa͒. 16,19 The deposition rate was 5-10 nm/s. A quartz microbalance was used to monitor the rate of deposition and the thickness of the metal film.…”

Section: A Infrared Fiber Tipsmentioning

confidence: 99%

Pattern characterization of deep-ultraviolet photoresists by near-field infrared microscopy

Dragnea

Preusser

Szarko

et al. 2001

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Partially hydrogenated poly(vinyl phenol) based photoresist for near UV, high aspect ratio micromachining Chemical contrast at subwavelength spatial resolution ͑/10͒ is achieved using a fiber-based, infrared near-field microscope, at 3 m wavelength. Chemically amplified polymer photoresists ͑poly͑t-butylmethacrylate͒͒, patterned by ultraviolet radiation and 250 nm thick, are imaged using infrared ͑IR͒ wavelengths situated around the OH stretch band of the polymer, a region sensitive to photochemical changes associated with latent image formation. The key technical points that enable near-field infrared absorption measurements down to 0.05% absorption sensitivity are discussed together with the major contrast mechanisms involved in image formation. The measurements are complemented by confirming studies using confocal infrared microscopy and depth profiling. The exposure dose dependence of the acid catalyzed chemistry, after the postexposure bake step, was studied on line/space patterned samples. The OH subgroup absorption maps of the patterned polymer film exhibit features that are not present in the topographical changes ͑shrinkage͒ induced by the postexposure polymer chemistry and illustrate significant potential of the IR near-field microscopy as an analytical tool for polymer chemical physics.

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Transmission near-field scanning microscope for infrared chemical imaging

Cited by 34 publications

References 17 publications

Spectroscopic infrared scanning near-field optical microscopy (IR-SNOM)

Spectroscopic infrared scanning near-field optical microscopy (IR-SNOM)

On contrast parameters and topographic artifacts in near-field infrared microscopy

Pattern characterization of deep-ultraviolet photoresists by near-field infrared microscopy

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