Home About us Contact | |||
Lateral Resolution (lateral + resolution)
Selected AbstractsRaman spectroscopic and X-ray investigation of stressed states in diamond-like carbon filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1-2 2005R. Krawietz Abstract The non-destructive characterization of intrinsic stress is very important to evaluate the reliability of devices based on diamond-like carbon (DLC) films. Whereas the only requirement for the X-ray diffraction method is a crystalline state of specimen, Raman spectroscopic stress analysis is restricted to materials showing intensive and sharp Raman peaks. On the other hand, Raman spectroscopy offers the possibility to measure stress profiles with lateral resolution of about 1 micron. The results of stress measurements in DLC films using both X-ray diffraction and Raman spectroscopy are found in very good correspondence. Mean stress in carbon films consisting of very small crystallites on silicon substrates has been determined by measuring and fitting the stress profiles in the substrate near artificial vertical film edges. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microstructural Characterization of Lamellar Features in TiAl by FIB Imaging,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Dennis Peter A novel experimental procedure is introduced to determine phase fractions and the distribution of individual phases of TiAl-based two-phase alloys using the focused ion beam (FIB) technique. Two , -titanium aluminide alloys with a fine-grained duplex and a nearly lamellar microstructure are examined. The special FIB-based preparation procedure results in high contrast ion beam-induced images for all investigated alloys and allows to quantify the phase contents easily by automated microstructural analysis. Fine two-phase structures, e.g. lamellar colonies in , -TiAl, can be imaged in high resolution with respect to different phases. To validate the FIB-derived data, we compare them to results obtained with another method to determine phase fractions, electron back-scatter diffraction (EBSD). This direct comparison shows that the FIB-based technique generally provides slightly higher ,2 -fractions, and thus helps to overcome the limited lateral resolution near grain boundaries and interfaces associated with the conventional EBSD approach. Our study demonstrates that the FIB-based technique is a simple, fast, and more exact way to determine high resolution microstructural characteristics with respect to different phase constitutions in two-phase TiAl alloys and other such materials with fine, lamellar microstructures. [source] Conjugated Polymers: High-Resolution Scanning Near-Field Optical Lithography of Conjugated Polymers (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Mater. The fabrication of high-resolution nanostructures in both poly(p -phenylene vinylene), PPV, and a crosslinkable derivative of poly(9,9,-dioctylfluorene), F8, using scanning near-field optical lithography, is reported. The ability to draw complex, reproducible structures with 65000 pixels and lateral resolution below 60 nm (< ,/5) is demonstrated over areas up to 20 ,m × 20 ,m. Patterning on length-scales of this order is desirable for realizing applications both in organic nanoelectronics and nanophotonics. The technique is based on the site-selective insolubilization of a precursor polymer under exposure to the confined optical field present at the tip of an apertured near-field optical fiber probe. In the case of PPV, a leaving-group reaction is utilized to achieve insolubilization, whereas the polyfluorene is insolubilized using a photoacid initiator to create a crosslinked network in situ. For PPV, resolubilization of the features is observed at high exposure energies. This is not seen for the crosslinked F8 derivative, r-F8Ox, allowing us to pattern structures up to 200 nm in height. [source] High-Resolution Scanning Near-Field Optical Lithography of Conjugated PolymersADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Daniel Credgington The fabrication of high-resolution nanostructures in both poly(p -phenylene vinylene), PPV, and a crosslinkable derivative of poly(9,9,-dioctylfluorene), F8, using scanning near-field optical lithography, is reported. The ability to draw complex, reproducible structures with 65000 pixels and lateral resolution below 60 nm (< ,/5) is demonstrated over areas up to 20 ,m × 20 ,m. Patterning on length-scales of this order is desirable for realizing applications both in organic nanoelectronics and nanophotonics. The technique is based on the site-selective insolubilization of a precursor polymer under exposure to the confined optical field present at the tip of an apertured near-field optical fiber probe. In the case of PPV, a leaving-group reaction is utilized to achieve insolubilization, whereas the polyfluorene is insolubilized using a photoacid initiator to create a crosslinked network in situ. For PPV, resolubilization of the features is observed at high exposure energies. This is not seen for the crosslinked F8 derivative, r-F8Ox, allowing us to pattern structures up to 200 nm in height. [source] Nanometer-Scale Mapping of Elastic Modules in Biogenic Composites: The Nacre of Mollusk ShellsADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Haika Moshe-Drezner Abstract In this study, a newly developed nanoscale modulus mapping is applied in order to visualize the 2D-distribution of mechanical characteristics in the aragonitic nacre layer of Perna canaliculus (green mussel) shells. Modulus maps provide lateral resolution of about 10 nm. They allow the aragonitic mineral (CaCO3) tablets and the interfaces between them to be clearly resolved, which are filled by an organic substance (mainly beta-chitin). The experimental data are compared with finite element simulations that also take into account the tip radius of curvature and the thickness of organic layers, as measured by means of scanning electron microscopy with back-scattered electrons. Based on this comparison, the Young modulus of beta-chitin is extracted. The obtained number, E, = 40 GPa, is higher than previously evaluated. The collected maps reveal that the elastic modules in the nacre layer change gradually across the ceramic/organic interfaces within a spatial range four times wider than the thickness of the organic layers. This is possibly due to inhomogeneous distribution of organic macromolecules within ceramic tablets. According to the data, the concentration of macromolecules gradually increases when approaching the organic/ceramic interfaces. A behavior of this type is unique to biogenic materials and distinguishes them from synthetic composite materials. Finally, three possible mechanisms that attempt to explain why gradual changes of elastic modules significantly enhance the overall resistance to fracture of the nacre layer are briefly discussed. The experimental findings support the idea that individual ceramic tablets, comprising the nacre, are built of the compositionally and functionally graded ceramic material. This sheds additional light on the origin of the superior mechanical properties of biogenic composites. [source] Non-uniqueness with refraction inversion , the Mt Bulga shear zoneGEOPHYSICAL PROSPECTING, Issue 4 2010Derecke Palmer ABSTRACT The tau-p inversion algorithm is widely employed to generate starting models with many computer programs that implement refraction tomography. However, this algorithm can frequently fail to detect even major lateral variations in seismic velocities, such as a 50 m wide shear zone, which is the subject of this study. By contrast, the shear zone is successfully defined with the inversion algorithms of the generalized reciprocal method. The shear zone is confirmed with a 2D analysis of the head wave amplitudes, a spectral analysis of the refraction convolution section and with numerous closely spaced orthogonal seismic profiles recorded for a later 3D refraction investigation. Further improvements in resolution, which facilitate the recognition of additional zones with moderate reductions in seismic velocity, are achieved with a novel application of the Hilbert transform to the refractor velocity analysis algorithm. However, the improved resolution also requires the use of a lower average vertical seismic velocity, which accommodates a velocity reversal in the weathering. The lower seismic velocity is derived with the generalized reciprocal method, whereas most refraction tomography programs assume vertical velocity gradients as the default. Although all of the tomograms are consistent with the traveltime data, the resolution of each tomogram is comparable only with that of the starting model. Therefore, it is essential to employ inversion algorithms that can generate detailed starting models, where detailed lateral resolution is the objective. Non-uniqueness can often be readily resolved with head wave amplitudes, attribute processing of the refraction convolution section and additional seismic traverses, prior to the acquisition of any borehole data. It is concluded that, unless specific measures are taken to address non-uniqueness, the production of a single refraction tomogram that fits the traveltime data to sufficient accuracy does not necessarily demonstrate that the result is either correct, or even the most probable. [source] The feasibility of electromagnetic gradiometer measurementsGEOPHYSICAL PROSPECTING, Issue 3 2001Daniel Sattel The quantities measured in transient electromagnetic (TEM) surveys are usually either magnetic field components or their time derivatives. Alternatively it might be advantageous to measure the spatial derivatives of these quantities. Such gradiometer measurements are expected to have lower noise levels due to the negative interference of ambient noise recorded by the two receiver coils. Error propagation models are used to compare quantitatively the noise sensitivities of conventional and gradiometer TEM data. To achieve this, eigenvalue decomposition is applied on synthetic data to derive the parameter uncertainties of layered-earth models. The results indicate that near-surface gradient measurements give a superior definition of the shallow conductivity structure, provided noise levels are 20,40 times smaller than those recorded by conventional EM instruments. For a fixed-wing towed-bird gradiometer system to be feasible, a noise reduction factor of at least 50,100 is required. One field test showed that noise reduction factors in excess of 60 are achievable with gradiometer measurements. However, other collected data indicate that the effectiveness of noise reduction can be hampered by the spatial variability of noise such as that encountered in built-up areas. Synthetic data calculated for a vertical plate model confirm the limited depth of detection of vertical gradient data but also indicate some spatial derivatives which offer better lateral resolution than conventional EM data. This high sensitivity to the near-surface conductivity structure suggests the application of EM gradiometers in areas such as environmental and archaeological mapping. [source] Preparation of Metallic Films on Elastomeric Stamps and Their Application for Contact Processing and Contact Printing,ADVANCED FUNCTIONAL MATERIALS, Issue 2 2003H. Schmid Abstract The formation of permanent or reversible metallic patterns on a substrate has applications in microfabrication and analytical techniques. Here, we investigate how to metallize an elastomeric stamp, either for processing of a substrate mediated by the proximity between the metal on the stamp and an active layer on the substrate, or for contact printing of the metal from a stamp to a substrate. The stamps were made from poly(dimethylsiloxane) (PDMS) and were modified before metallizing them with Au by adding to or removing from their bulk mobile silicone residues, by oxidizing their surface with an O2 -plasma, by surface-fluorination via silanization, or by priming them with a Ti layer. The interplay between the adhesion of the different layers defines two categories of application: contact processing and contact printing. Contact processing corresponds to keeping the metal on the stamp after contacting a substrate; it is reversible and nondestructive, and useful to define transient electrical contacts or quench fluorescence on a surface, for example. Contact printing occurs when the metal on the stamp adheres to the printed surface. Contact printing can transfer a metal, layers of metals, or an oxide onto a substrate with submicrometer lateral resolution. The transfer can be total or localized to the regions of contact, depending on the morphology of the metal on the stamp and/or the surface chemistry of the substrate. [source] The Colours of MoleculesIMAGING & MICROSCOPY (ELECTRONIC), Issue 1 2006Chemical Force Microscopy Enables a New Look on Surfaces Abstract As the surface functionality is gaining more and more relevance in modern surface technology, the need for an analytical tool with chemical sensitivity and high lateral resolution is becoming important more than ever. In this article, we introduce the novel method "Chemical Force Microscopy" (CFM), which is enabling the chemical mapping of the surface with nm-resolution for the first time. This method has proved to be efficient to optimise and understand different processes on industrial surfaces. In the fields like plasma, coating, cell biology, pharmaceutical and printing technologies, this method has shown to be supremely efficient. [source] Sub-100-nanometre resolution in total internal reflection fluorescence microscopyJOURNAL OF MICROSCOPY, Issue 1 2008M. BECK Summary Combining total internal reflection fluorescence microscopy with structured illumination allows optical wide-field imaging with sub-100-nanometre resolution. We present a novel objective-launch set-up for standing wave illumination that takes advantage of a tunable transmission diffraction grating and transparent phase shifters actuated by electro-active polymers to control the excitation pattern in three dimensions. Image acquisition is completed in less than 1 s. To reconstruct the extended image spectrum, we apply a new apodization function that results in a lateral resolution of 89 nm for green emission wavelength. [source] Near-field scanning optical microscopy and near-field induced photocurrent investigations of buried heterostructure multiquantum well lasersJOURNAL OF MICROSCOPY, Issue 3 2005M. P. ACKLAND Summary Buried heterostructure multiquantum well laser devices are investigated utilizing a near-field scanning optical microscope to characterize and correlate the surface topography, optical output and electronic properties of the device. Near-field photocurrent imaging has been used to accurately measure the unbiased buried heterostructure multiquantum well device in cross-section, successfully revealing the distribution of pn -junctions and their associated fields. Moreover, this has been accurately correlated with the physical structure of the device determined by simultaneous shear-force imaging of the surface. Topographic structure is manifested as a result of strain relaxation (,10,10 m) of the cleaved cross-section. These imaging modes are similarly correlated with the optical output of the operational device mapped with 50 nm lateral resolution. The collection-mode measurements detected electroluminescence external to the active region, highlighting the existence of carrier recombination away from the multiquantum well device region. The combination and correlation of different near-field scanning optical microscope imaging modes proved powerful in the analysis of the buried heterostructure multiquantum well device, and was shown to assist in the identification of current leakage pathways within the structure. [source] Upconversion fluorescence imaging of erbium-doped fluoride glass particles by apertureless SNOMJOURNAL OF MICROSCOPY, Issue 3 2003A. Fragola Abstract We have imaged fluorescent erbium-doped fluoride glass particles by apertureless scanning near-field optical microscopy. The optical excitation has been performed at , = 780 nm whereas fluorescence emission has been collected around , = 550 nm. This process, called upconversion by energy transfer, involves two erbium ions and is not linear. Besides an improvement of the lateral resolution, we have observed on some particles that the fluorescence is not homogeneously distributed, but is rather localized in some zones brighter than others. By making tip approach curves, we have also observed that the amount of fluorescence intensity scattered by the tip is increasing when the tip is approaching the sample surface. [source] Tip-Enhanced Raman SpectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2009V. Deckert Abstract This special issue of the Journal of Raman Spectroscopy deals with the advances of Tip-Enhanced Raman Spectroscopy (TERS) since its experimental verification about 10 years ago. The contributed papers reflect a snapshot of current research related to experimental, theoretical and, last but not least, application-oriented advances in this field. The contributions highlight the fact that TERS is a very active field of research and, while the rewards with respect to lateral resolution and detection limits are intriguing, great care is necessary to avoid the pitfalls related either to the experimental design or to the interpretation of data. This special issue intends to provide the basis for a further step towards a standardised approach to TERS. Copyright © 2009 John Wiley & Sons, Ltd. [source] Correlating Raman peak shifts with phase transformation and defect densities: a comprehensive TEM and Raman study on siliconJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2009Thomas Wermelinger Abstract Silicon is the most often used material in micro electromechanical systems (MEMS). Detailed understanding of its mechanical properties as well as the microstructure is crucial for the reliability of MEMS devices. In this paper, we investigate the microstructure changes upon indentation of single crystalline (100) oriented silicon by transmission electron microscopy (TEM) and Raman microscopy. TEM cross sections were prepared by focused ion beam (FIB) at the location of the indent. Raman microscopy and TEM revealed the occurrence of phase transformations and residual stresses upon deformation. Raman microscopy was also used directly on the cross-sectional TEM lamella and thus microstructural details could be correlated to peak shape and peak position. The results show, however, that due to the implanted Ga+ ions in the lamella the silicon Raman peak is shifted significantly to lower wavenumbers. This hinders a quantitative analysis of residual stresses in the lamella. Furthermore, Raman microscopy also possesses the ability to map deformation structures with a lateral resolution in the submicron range. Copyright © 2009 John Wiley & Sons, Ltd. [source] Optically controlled adaptive mirrorLASER PHYSICS LETTERS, Issue 11 2004F. Reinert Abstract We report on an adaptive mirror system that allows generating thermo-optically controlled wavefront corrections. The influence of the wavefront is based on the thermal dependence of the refractive index in a thin active layer. The thermal pattern in the active layer is generated by irradiation with a diode laser emitting at 805 nm. The active layer consists of a diluted aqueous solution of NdCl3. A Michelson interferometer is used to measure the wavefront distortions. A phase shift of 6, with a lateral resolution of better than 1 mm and a temporal rise/fall time of a few seconds can be achieved with an absorbed power of only 150 mW at an intensity of about 10 W/cm2. (© 2004 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Spatial refractive index measurement of porcine artery using differential phase optical coherence microscopyLASERS IN SURGERY AND MEDICINE, Issue 10 2006Jeehyun Kim PhD Abstract Background and Objectives We describe a methodology to record spatial variation of refractive index of porcine renal artery using differential phase optical coherence microscopy (DP-OCM). Study Design/Materials and Methods The DP-OCM provides quantitative measurement of thin specimen phase retardation and refractive index by measuring optical path-length changes on the order of a few nanometers and with a lateral resolution of 3 µm. The DP-OCM instrumentation is an all-fiber, dual-channel Michelson interferometer constructed using a polarization maintaining (PM) fiber. Results Two-dimensional en face dual-channel phase images are taken over a 150,×,200 µm region on a microscopic slide, and the images are reconstructed by plotting a two-dimensional refractive index map as the OCM beam is moved across the sample. Conclusions Because the DP-OCM can record transient changes in the optical path-length, the system may be used to record quantitative optical path-length alterations of tissue in response to various stimuli. A fiber-based DP-OCM may have the potential to substantially improve in vivo imaging of individual cells for a variety of clinical diagnostics, and monitoring applications. Lasers Surg. Med. © 2006 Wiley-Liss, Inc. [source] Demonstration of high lateral resolution in laser confocal microscopy using annular and radially polarized lightMICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2009Jeongyong Kim Abstract The authors present the experimental result of improved lateral resolution in laser confocal microscopy (LCM) by using annular and radially polarized light as the input illumination of an existing LCM. The authors examined the lateral resolution of the LCM by imaging a single fluorescent bead and measuring the lateral width of the single bead profile appearing in the optical image. Compared to no aperture and linearly polarized light, the central peak of the single bead profile narrowed by ,40%, being as small as 122 nm in full width at half maximum using 405 nm laser excitation in a reflection imaging. In addition, the authors showed that radial polarization helps to preserve the circular shape of the single bead profile whereas linearly polarized light tends to induce an elongation along the polarization direction. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc. [source] Super-resolution bright-field optical microscopy based on nanometer topographic contrastMICROSCOPY RESEARCH AND TECHNIQUE, Issue 4-5 2004Shu-Wei Huang Abstract By using an expectation-maximization maximum likelihood estimation algorithm to improve the lateral resolution of a recently developed non-interferometric wide-field optical profilometer, we obtain super-resolution bright-field optical images of nanometer features on a flat surface. The optical profilometer employs a 365-nm light source and an ordinary objective lens of a 0.95 numerical aperture. For objects of 100 nm thickness, lateral features about ,/7 can be resolved in the restored images without fluorescence labeling. Current image acquisition rate is 0.1 frame/sec, which is limited by the brightness of the light source. With a brighter light source, the imaging speed can be fast enough for real-time observation of dynamic activities in the nanometer scale. Microsc. Res. Tech. 65:180,185, 2004. © 2005 Wiley-Liss, Inc. [source] Carbon nanotube probe resolution: a quantitative analysis using Fourier TransformPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2004H. R. Gutiérrez Abstract A method to quantify the resolution of atomic force microscopy (AFM) probes using Fourier analysis of the AFM images is proposed. The maximum detectable spatial frequency obtained from the power spectrum was used to estimate the lateral resolution. Carbon nanotube tips were successfully used to study very dense arrays of semiconductor nanostructures. In particular, accurate measurements of shallow facet angles were obtained, which are in perfect agreement with results obtained by two complementary techniques , High Resolution Transmission Electron Microscopy and Reflection High-Energy Electron Diffraction. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nondestructive topographic resistivity evaluation of semi-insulating SiC substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2003R. Stibal Abstract Semi-insulating silicon carbide single crystals have been grown using high temperature chemical vapor deposition without vanadium doping. The resistivity of standard and exploratory 2, diameter substrates has been analysed topographically with 1 mm lateral resolution with an improved contactless resistivity mapping technique. Absolute resistivity values are ranging from below 1 × 105 to above 1 × 1012 , cm. The lateral homogeneity of state-of-the-art material is very satisfactory, whereas strong localized inhomogeneities in exploratory materials underscore the decisive advantage of a nondestructive and topographic resistivity evaluation in supporting the optimization of the crystal growth procedure. [source] Matrix vapor deposition/recrystallization and dedicated spray preparation for high-resolution scanning microprobe matrix-assisted laser desorption/ionization imaging mass spectrometry (SMALDI-MS) of tissue and single cellsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 3 2010Werner Bouschen Matrix preparation techniques such as air spraying or vapor deposition were investigated with respect to lateral migration, integration of analyte into matrix crystals and achievable lateral resolution for the purpose of high-resolution biological imaging. The accessible mass range was found to be beyond 5000 u with sufficient analytical sensitivity. Gas-assisted spraying methods (using oxygen-free gases) provide a good compromise between crystal integration of analyte and analyte migration within the sample. Controlling preparational parameters with this method, however, is difficult. Separation of the preparation procedure into two steps, instead, leads to an improved control of migration and incorporation. The first step is a dry vapor deposition of matrix onto the investigated sample. In a second step, incorporation of analyte into the matrix crystal is enhanced by a controlled recrystallization of matrix in a saturated water atmosphere. With this latter method an effective analytical resolution of 2,µm in the x and y direction was achieved for scanning microprobe matrix-assisted laser desorption/ionization imaging mass spectrometry (SMALDI-MS). Cultured A-498 cells of human renal carcinoma were successfully investigated by high-resolution MALDI imaging using the new preparation techniques. Copyright © 2010 John Wiley & Sons, Ltd. [source] 2114: AO adapted to SD-OCTACTA OPHTHALMOLOGICA, Issue 2010W DREXLER Purpose Optical coherence tomography (OCT) has emerged as a leading technique in ophthalmic imaging due to its capability to non-invasively resolve tissue morphology with high sensitivity and high axial resolution. Despite increases in axial resolution, monochromatic ocular aberrations limited the transverse resolution for retinal imaging to ~20 ,m, which is too large for visualization of cellular structures. Adaptive optics (AO) may be used to correct such aberrations, leading to an improvement in image contrast and lateral resolution. Methods A successful combination of ultra-high speed (120,000 depth scans/s), ultra-high resolution optical coherence tomography with adaptive optics and an achromatizing lens for compensation of monochromatic and longitudinal chromatic ocular aberrations, respectively, allows for non-invasive volumetric imaging in normal and pathologic human retinas at cellular resolution. Results The capability of this imaging system is demonstrated through preliminary studies by probing cellular intraretinal structures that have not been accessible so far with in vivo, non-invasive, label-free imaging techniques, including pigment epithelial cells, micro-vasculature of the choriocapillaris, single nerve fibre bundles and collagenous plates of the lamina cribrosa in the optic nerve head. In addition, the volumetric extent of cone loss in two colour-blinds can be quantified for the first time. Conclusion AO OCT might provide opportunities to enhance the understanding of retinal pathogenesis and early diagnosis of retinal diseases. Commercial interest [source] |