| 1. |
- Bergqvist, Jonas, et al.
(författare)
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LED array scanner for inline characterization of thin film photovoltaic modules
- 2016
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier. - 0927-0248 .- 1879-3398. ; 157:17, s. 1057-1064
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Tidskriftsartikel (refereegranskat)abstract
- Thin film solar cells, and in particular printed organic solar cells, offer a potential route to a low cost power generation from sunlight. However, manufacturing these solar cells rapidly generates large areas that have to be characterized, preferably in-line for a direct feed back in the production process. Here we introduce the LEDimage, a LED array illumination induced photocurrent method suitable for high speed inline characterization and defect detection of organic solar cell modules. The LEDimage enables simultaneous illumination of all connected subcells without additional bias light. Each LED in the array is amplitude modulated at an individual frequency and the photocurrent response is Fourier transformed to generate a photocurrent map. Furthermore, the LEDimage can be used as a hand scanner for fast device characterization. We expect that LEDimage can be an effective research and industry tool for characterization of large area thin film solar cells.
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| 2. |
- Forchheimer, Daniel, et al.
(författare)
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Model-based extraction of material properties in multifrequency atomic force microscopy
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 85:19, s. 195449-
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Tidskriftsartikel (refereegranskat)abstract
- We present a method to reconstruct the nonlinear tip-surface force and extract material properties from a multifrequency atomic force microscopy (AFM) measurement with a high-quality-factor cantilever resonance. In a measurement time of similar to 2 ms, we are able to accurately reconstruct the tip-surface force-displacement curve, allowing simultaneous high-resolution imaging of both topography and material properties at typical AFM scan rates. We verify the method using numerical simulations, apply it to experimental data, and use it to image mechanical properties of a polymer blend. We further discuss the limitations of the method and identify suitable operating conditions for AFM experiments.
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| 3. |
- Forchheimer, Daniel, et al.
(författare)
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Simultaneous imaging of surface and magnetic forces
- 2013
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 103:1, s. 013114-
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate quantitative force imaging of long-range magnetic forces simultaneously with near-surface van-der-Waals and contact-mechanics forces using intermodulation atomic force microscopy. Magnetic forces at the 200 pN level are separated from near-surface forces at the 30 nN level. Imaging of these forces is performed in both the contact and non-contact regimes of near-surface interactions.
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| 4. |
- Platz, Daniel, et al.
(författare)
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Effect of material stiffness on intermodulation response in dynamic atomic force microscopy
- 2010
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Ingår i: ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. - New York : Amer Soc Mechanical Engineers. ; , s. 499-506
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Konferensbidrag (refereegranskat)abstract
- We perform simulations and experiments on an oscillating atomic force microscope cantilever approaching a surface, where the intermodulation response of the cantilever driven with two pure harmonic tones is investigated. In the simulations, the tip and surface interact with a conservative nonlinear force, and the parameter space of approach distance and surface stiffness is explored. Approach experiments are carried out on three surfaces with widely varying stiffness. Qualitative similarities between simulations and experiment can be seen, but quantitative comparison is difficult due to the overly idealized tip-surface force model used in the simulation.
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| 5. |
- Platz, Daniel, et al.
(författare)
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Interaction imaging with amplitude-dependence force spectroscopy
- 2013
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4, s. 1360-
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of surface forces is the key to understanding a large number of processes in fields ranging from physics to material science and biology. The most common method to study surfaces is dynamic atomic force microscopy (AFM). Dynamic AFM has been enormously successful in imaging surface topography, even to atomic resolution, but the force between the AFM tip and the surface remains unknown during imaging. Here we present a new approach that combines high-accuracy force measurements and high-resolution scanning. The method, called amplitude-dependence force spectroscopy (ADFS), is based on the amplitude dependence of the cantilever's response near resonance and allows for separate determination of both conservative and dissipative tip-surface interactions. We use ADFS to quantitatively study and map the nano-mechanical interaction between the AFM tip and heterogeneous polymer surfaces. ADFS is compatible with commercial atomic force microscopes and we anticipate its widespread use in taking AFM toward quantitative microscopy.
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| 6. |
- Platz, Daniel, et al.
(författare)
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Interpreting motion and force for narrow-band intermodulation atomic force microscopy
- 2013
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Ingår i: Beilstein Journal of Nanotechnology. - : Beilstein Institut. - 2190-4286. ; 4, s. 45-56
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Tidskriftsartikel (refereegranskat)abstract
- Intermodulation atomic force microscopy (ImAFM) is a mode of dynamic atomic force microscopy that probes the nonlinear tip-surface force by measurement of the mixing of multiple modes in a frequency comb. A high-quality factor cantilever resonance and a suitable drive comb will result in tip motion described by a narrow-band frequency comb. We show, by a separation of time scales, that such motion is equivalent to rapid oscillations at the cantilever resonance with a slow amplitude and phase or frequency modulation. With this time-domain perspective, we analyze single oscillation cycles in ImAFM to extract the Fourier components of the tip-surface force that are in-phase with the tip motion (F-I) and quadrature to the motion (F-Q). Traditionally, these force components have been considered as a function of the static-probe height only. Here we show that F-I and F-Q actually depend on both static-probe height and oscillation amplitude. We demonstrate on simulated data how to reconstruct the amplitude dependence of F-I and F-Q from a single ImAFM measurement. Furthermore, we introduce ImAFM approach measurements with which we reconstruct the full amplitude and probe-height dependence of the force components F-I and F-Q, providing deeper insight into the tip-surface interaction. We demonstrate the capabilities of ImAFM approach measurements on a polystyrene polymer surface.
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| 7. |
- Platz, Daniel, et al.
(författare)
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Polynomial force approximations and multifrequency atomic force microscopy
- 2013
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Ingår i: Beilstein Journal of Nanotechnology. - : Beilstein Institut. - 2190-4286. ; 4:1, s. 352-360
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Tidskriftsartikel (refereegranskat)abstract
- We present polynomial force reconstruction from experimental intermodulation atomic force microscopy (ImAFM) data. We study the tip-surface force during a slow surface approach and compare the results with amplitude-dependence force spectroscopy (ADFS). Based on polynomial force reconstruction we generate high-resolution surface-property maps of polymer blend samples. The polynomial method is described as a special example of a more general approximative force reconstruction, where the aim is to determine model parameters that best approximate the measured force spectrum. This approximative approach is not limited to spectral data, and we demonstrate how it can be adapted to a force quadrature picture.
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| 8. |
- Platz, Daniel, et al.
(författare)
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The role of nonlinear dynamics in quantitative atomic force microscopy
- 2012
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 23:26, s. 265705-
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Tidskriftsartikel (refereegranskat)abstract
- Various methods of force measurement with the atomic force microscope are compared for their ability to accurately determine the tip-surface force from analysis of the nonlinear cantilever motion. It is explained how intermodulation, or the frequency mixing of multiple drive tones by the nonlinear tip-surface force, can be used to concentrate the nonlinear motion in a narrow band of frequency near the cantilever's fundamental resonance, where accuracy and sensitivity of force measurement are greatest. Two different methods for reconstructing tip-surface forces from intermodulation spectra are explained. The reconstruction of both conservative and dissipative tip-surface interactions from intermodulation spectra are demonstrated on simulated data.
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| 9. |
- Platz, Daniel, et al.
(författare)
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Tip-surface interactions in dynamic atomic forcemicroscopy
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In atomic force microscopy (AFM) tip-surface interactions are usuallyconsidered as functions of the tip position only, so-called force curves. However,tip-surface interactions often depend on the tip velocity and the past tip trajectory.Here, we introduce a compact and general description of these interactionsappropriate to dynamic AFM where the measurement of force is restricted toa narrow frequency band. We represent the tip-surface interaction in termsof a force disk in the phase space of position and velocity. Determination ofthe amplitude dependence of tip-surface forces at a fixed static probe heightallows for a comprehensive treatment of conservative and dissipative interactions.We illuminate the fundamental limitations of force reconstruction with narrowband dynamic AFM and we show how the amplitude dependence of the F ouriercomponent of the force at the tip oscillation frequency, gives qualitative insight intothe detailed nature of the tip-surface interaction. With minimal assumptions thisamplitude dependence force spectroscopy allows for a quantitative reconstruction ofthe effective conservative tip-surface force as well as a position-dependent dampingfactor. We demonstrate this reconstruction on simulated intermodulation AFMdata.
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| 10. |
- Sanandaji, Nima, et al.
(författare)
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Inkjet printing as a possible route to study confined crystal structures
- 2012
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 49:1, s. 203-208
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Tidskriftsartikel (refereegranskat)abstract
- Inkjet printing is a technique for the precise deposition of liquid droplets in the pL-volume range in well-defined patterns. Previous studies have shown that inkjet printing is attractive in polymer technology since it permits the controlled deposition of functional polymer surfaces. We suggest that the technique might also be useful for studying crystallization, in particular confined crystallization. Inkjet printing is a non-contact deposition method with minimal risk of contamination, which allows the exact deposition of both polymer solutions and polymer melts. This paper demonstrates the possibility of utilizing the technique to create surfaces where polymer chains form isolated small structures. These structures were confined by both the low polymer content in each droplet and the time constraint on crystal formation that arose as the result of the rapid solvent evaporation from the pL-sized droplets. In theory, inkjet printing enables the exact deposition of systems with as few as a single polymer chain in the average droplet. With appropriate instrumentation, the versatile inkjet technology can be utilized to create whole surfaces covered with polymer structures formed by the crystallization of small, dilute and rapidly evaporating droplets. 110 pL droplets of a 10 -6 g L -1 poly(ε-caprolactone) solution in 1-butanol have been deposited and studied by atomic force microscopy. Small structures of ca. 10 nm thickness and ca. 50 nm diameter also seemed to exhibit crystalline features. Some of the small structures had unusual rectangular forms whilst others were interpreted to be early precursors to six-sided single crystals previously observed for poly(ε-caprolactone). The unusual forms observed may have resulted from the entrapment of crystal structures into metastable phases, due to the limited amount of polymer material present and the rapid evaporation of the droplets.
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