Search results for "Vector"
showing 10 items of 2660 documents
Spin-polarized scanning tunneling microscopy and spectroscopy of ultrathinFe∕Mo(110)films usingW∕Au∕Cotips
2006
We report on magnetic contrast observed in low-temperature spin-polarized scanning tunneling microscopy (SP-STM) of Fe nanowires deposited on Mo(110) using tungsten tips covered by $\mathrm{Au}∕\mathrm{Co}$ thin films. Due to the spin reorientation transition of Co films on Au an out-of-plane magnetic sensitivity is obtained for tips with thin cobalt films (up to 8 monolayers of Co), while for thicker Co coverages an in-plane magnetization component can be probed. Using $\mathrm{W}∕\mathrm{Au}∕\mathrm{Co}$ tips with out-of-plane magnetic sensitivity we show that the one (ML) and two (DL) atomic layers thick Fe nanowires prepared using step flow growth on a Mo(110) crystal are perpendicularl…
Development and analysis of a model based on chirped fiber Bragg gratings employed for cracks characterization in materials
2018
In this work a model was developed that allows to understand the behavior of a chirped fiber Bragg grating for the detection and characterization of cracks in materials. In addition to the amplitude response, we show that the group delay of the grating provides useful information for the characterization of the crack. The position of the crack can be determined thanks to the linear chirp of the grating that fixes a correlation between the spatial position and both, the wavelength and the group delay. However, our analysis shows that this simple approach has a source of error, which can be overcome if a controllable external strain can be applied to the embedded grating, additional to the st…
Direct observation of smectic layers in side chain liquid crystal polymer films
1987
Abstract By applying stringent conditions to the imaging process it has been possible to produce electron micrographs of the smectic planes in a highly beam sensitive polymethcrylate side chain liquid crystal polymer. These planes show a high degree of internal perfection, while, at the same time, showing clear evidence of curvature. The director orientation was determined over a fairly large region.
Diamond Magnetic Microscopy of Malarial Hemozoin Nanocrystals.
2019
Magnetic microscopy of malarial hemozoin nanocrystals was performed using optically detected magnetic resonance imaging of near-surface diamond nitrogen-vacancy centers. Hemozoin crystals were extracted from $Plasmodium$-$falciparum$-infected human blood cells and studied alongside synthetic hemozoin crystals. The stray magnetic fields produced by individual crystals were imaged at room temperature as a function of applied field up to 350 mT. More than 100 nanocrystals were analyzed, revealing the distribution of their magnetic properties. Most crystals ($96\%$) exhibit a linear dependence of stray field magnitude on applied field, confirming hemozoin's paramagnetic nature. A volume magneti…
Mixed Mode Delamination Analysis by a Thermodynamically Consistent Cohesive Interface Model with Independent Mode I and Mode II Fracture Energies
2015
Abstract In the present paper a new thermodynamically consistent cohesive interface model is proposed; it based on a predefined Helmhotz free energy with a single scalar damage variable and produces two independent fracture energies, in pure mode I and pure mode II debonding conditions. The proposed model can also take in to account the frictional effects with a smooth transition of the mechanical behaviour, from the initial cohesive one of the sound material, to the frictional one of the fully debonded interface. The cohesive-frictional behaviour is based on the mesoscale geometric interpretation of the scalar damage variable, which distinguish sound and debonded fractions of a representat…
Wave-Vector Dependence of the Dynamics in Supercooled Metallic Liquids
2020
Physical review letters 125(5), 055701 (2020). doi:10.1103/PhysRevLett.125.055701
Wave-vector analysis of plasmon-assisted distributed nonlinear photoluminescence along Au nanowires
2020
We report a quantitative analysis of the wavevector diagram emitted by nonlinear photoluminescence generated by a tightly focused pulsed laser beam and distributed along Au nanowire via the mediation of surface plasmon polaritions. The nonlinear photoluminescence is locally excited at key locations along the nanowire in order to understand the different contributions constituting the emission pattern measured in a conjugate Fourier plane of the microscope. Polarization-resolved measurements reveal that the nanowire preferentially emits nonlinear photoluminescence polarized transverse to the long axis at close to the detection limit wavevectors with a small azimuthal spread in comparison to …
Grafted polymer layers under shear: A Monte Carlo simulation
1993
Endgrafted polymers at surfaces exposed to a shear flow are modeled by a nonequilibrium Monte Carlo method where the jump rate of effective monomers to neighboring lattice sites against the flow direction is smaller than in the flow direction, assuming that this difference in jump rates is proportional to the local velocity of the flowing fluid. In the dilute case of isolated chains, the velocity profile is assumed linearly increasing with the distance from the surface, while for the case of polymer brushes the screening of the velocity field is calculated using a parabolic density profile for the brush whose height is determined self‐consistently. Linear dimensions of isolated chains are o…
Imaging Symmetry-Selected Corner Plasmon Modes in Penta-Twinned Crystalline Ag Nanowires
2011
International audience; Using dual-plane leakage radiation microscopy, we investigate plasmon propagation in individual penta-twinned crystalline silver nanowires. By measuring the wavevector content of the light emitted in the substrate, we unambiguously determine the effective index and the losses of the mode propagating in these structures. The experimental results, in particular, the unexpectedly low effective index, reveal the direct influence of the nanowire crystallinity and pentagonal structure on the observed plasmon modes. By analogy with molecular orbitals of similar symmetry, the plasmon modes are also determined numerically in good agreement with the observed values. We further…
Minority Carrier Lifetime Variations in Multicrystalline Silicon Wafers with Temperature and Ingot Position
2017
The minority carrier lifetimes of multicrystalline silicon wafers are mapped using microwave photoconductive decay for different temperatures and ingot positions. Wafers from the top of the ingot display larger areas with lower lifetimes compared to wafers from the bottom. The lifetimes of low-lifetime areas are found to increase with the temperature, while the lifetimes of some high-lifetime areas decrease or remain unchanged. The relative improvement of the low-lifetime areas is considerably larger than the relative change in the high-lifetime areas. We suggest that the above-mentioned observations explain, at least partially, why previous studies have found the relative temperature coeff…