| 1. |
- Farahi, R. H., et al.
(författare)
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Microscale Marangoni actuation : All-optical and all-electrical methods
- 2006
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 106:8-9, s. 815-821
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental results from an all-optical microfluidic platform that may be complimented by a thin film all-electrical network. Using these configurations we have studied the microfluidic convective flow systems of silicone oil, glycerol, and 1,3,5-trinitrotoluene on open surfaces through the production of surface tension gradients derived from thermal gradients. We show that sufficient localized thermal variation can be created utilizing surface plasmons and/or engaging individually addressable resistive thermal elements. Both studies manipulate fluids via Marangoni forces, each having their unique exploitable advantages. Surface plasmon excitation in metal foils are the driving engine of many physical-, chemical-, and bio-sensing applications. Incorporating, for the first time, the plasmon concept in microfluidics, our results thus demonstrate great potential for simultaneous fluid actuation and sensing. (c) 2006 Elsevier B.V. All rights reserved.
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| 2. |
- Forsberg, Johan, et al.
(författare)
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A versatile soft x-ray transmission system for time resolved in situ microscopy with chemical contrast
- 2009
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 109:9, s. 1157-1163
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Tidskriftsartikel (refereegranskat)abstract
- We present the design and operation of a versatile soft X-ray transmission system for time resolved in situ microscopy with chemical contrast. The utility of the setup is demonstrated by results from following a corrosion process of iron in saline environment, subjected to a controlled humid atmosphere. The system includes a transmission flow-cell reactor that allows for in situ microscopic probing with soft X-rays. We employ a full field technique by using a nearly collimated X-ray beam that produces an unmagnified projection of the transmitted soft X-rays (below 1.1 keV) which is magnified and recorded by an optical CCD camera. Time lapse series with chemical contrast allow us to follow and interpret the chemical processes in detail. The obtainable lateral resolution is a few mu m, sufficient to detect filiform corrosion on iron.
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| 3. |
- Hebert, C., et al.
(författare)
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Magnetic circular dichroism in electron energy loss spectrometry
- 2008
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 108:3, s. 277-284
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Tidskriftsartikel (refereegranskat)abstract
- The measurement of circular dichroism in the electron microscope is a new, emerging method and, as such, it is subject to constant refinement and improvement. Different ways can be envisaged to record the signal. We present an overview of the key steps in the energy-loss magnetic chiral dichroism (EMCD) experiment as well as a detailed review of the methods used in the intrinsic way where the specimen is used as a beam splitter. Lateral resolution up to 20-30 nm can be achieved, and the use of convergent beam techniques leads to an improved SIN ratio. Dichroic effects are shown for Ni and Co single crystal; as a counterexample, measurements were carried also for a non-magnetic (Ti) sample, where no dichroic effect was found.
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| 4. |
- McMullan, G, et al.
(författare)
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Electron imaging with medipix2 hybrid pixel detector
- 2007
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 107:4-5, s. 401-413
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Tidskriftsartikel (refereegranskat)abstract
- The electron imaging performance of Medipix2 is described. Medipix2 is a hybrid pixel detector composed of two layers. It has a sensor layer and a layer of readout electronics, in which each 55 μm×55 μm pixel has upper and lower energy discrimination and MHz rate counting. The sensor layer consists of a 300 μm slab of pixellated monolithic silicon and this is bonded to the readout chip. Experimental measurement of the detective quantum efficiency, DQE(0) at 120 keV shows that it can reach 85% independent of electron exposure, since the detector has zero noise, and the DQE(Nyquist) can reach 35% of that expected for a perfect detector (4/π2). Experimental measurement of the modulation transfer function (MTF) at Nyquist resolution for 120 keV electrons using a 60 keV lower energy threshold, yields a value that is 50% of that expected for a perfect detector (2/π). Finally, Monte Carlo simulations of electron tracks and energy deposited in adjacent pixels have been performed and used to calculate expected values for the MTF and DQE as a function of the threshold energy. The good agreement between theory and experiment allows suggestions for further improvements to be made with confidence. The present detector is already very useful for experiments that require a high DQE at very low doses.
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| 5. |
- Pillai, Saju, et al.
(författare)
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Effect of lateral morphology formation of polymer blend towards patterning silane-based SAMs using selective dissolution method
- 2008
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 108:5, s. 458-464
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Tidskriftsartikel (refereegranskat)abstract
- A number of strategies have been developed including soft lithography and photolithography for patterning various surfaces. Here we have discussed a customized strategy for surface patterning of nanosized, silane-based SAMs and monolayer thickness measurement investigated using atomic force microscope (AFM). We have utilized the versatile morphology of a binary polymer blend to generate patterned SAMs over silicon substrate by employing a selective dissolution procedure. This method was confirmed with different organosilanes with varying number of C-atoms and to other polymer blend. The samples were imaged both in tapping mode and pulsed force mode AFM.
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| 6. |
- Stoltz, Dunja, et al.
(författare)
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Scanning tunneling microscopy of Fe- and O-sublattices on Fe3O4(100)
- 2008
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 108:6, s. 540-544
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Tidskriftsartikel (refereegranskat)abstract
- We present scanning tunneling microscopy of an octahedral (B) plane terminated (root 2 x root 2)R45 degrees-reconstructed surface of a natural magnetite (10 0) crystal. Implementing a W-tip we achieve the same resolution on Fe rows as was reported in the past either with the use of antiferromagnetic tips or on magnetite (Fe3O4) films. We show images of Fe or O sublattices of Fe3O4 with atomic resolution.
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| 7. |
- Verbeeck, J., et al.
(författare)
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Optimal aperture sizes and positions for EMCD experiments
- 2008
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 108:9, s. 865-872
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Tidskriftsartikel (refereegranskat)abstract
- The signal-to-noise ratio (SNR) in energy-loss magnetic chiral dichroism (EMCD)-the equivalent of Xray magnetic circular dichroism (XMCD) in the electron microscope-is optimized with respect to the detector shape, size and position. We show that an important increase in SNR over previous experiments can be obtained when taking much larger detector sizes. We determine the ideal shape of the detector but also show that round apertures are a good compromise if placed in their optimal position. We develop the theory for a simple analytical description of the EMCD experiment and then apply it to dynamical multibeam Bloch wave calculations and to an experimental data set. In all cases it is shown that a significant and welcome improvement of the SNR is possible.
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| 8. |
- von Hofsten, Olov, et al.
(författare)
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Simulation of partially coherent image formation in a compact soft x-ray microscope
- 2007
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 107:8, s. 604-609
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we describe a numerical method of simulating two-dimensional images in a compact soft X-ray microscope using partially coherent illumination considerations. The work was motivated by recent test object images obtained by the latest generation inhouse compact soft X-ray microscope, which showed diffraction-like artifacts not observed previously. The numerical model approximates the condenser zone plate as a secondary incoherent source represented by individually coherent but mutually incoherent source points, each giving rise to a separate image. A final image is obtained by adding up all the individual source point contributions. The results are compared with the microscope images and show qualitative agreement, indicating that the observed effects are caused by partially coherent illumination.
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