Search results for "Microscopy"
showing 10 items of 3390 documents
History dependence of the magnetization of thin HTSC films: an explanation for distorted SQUID signals
1997
Abstract The magnetizations of thin film disk-shaped type-II superconductors in perpendicular magnetic fields are considered by aid of Mikheenko's critical state model which has been corrected by Zhu for the case of a time-varying periodic field. This paper presents the application of this scheme to an arbitrary nonperiodic time dependence H ( t ). We calculate the influence of field inhomogeneities in a magnetometer on the current density distribution of a disk-shaped type-II superconductor. The resulting SQUID pickup signals and magnetic moments are compared to measurements performed on a 200 nm thick YBa 2 Cu 3 O 7 film in the irreversible regime of the phase diagram. Theory and experime…
Field dependence of the vortex core size probed by scanning tunneling microscopy
2016
We study the spatial distribution of the density of states (DOS) at zero bias N(r) in the mixed state of single and multigap superconductors. We provide an analytic expression for N(r) based on deGennes' relationship between DOS and the order parameter that reproduces well scanning tunneling microscopy (STM) data in several superconducting materials. In the single gap superconductor β-Bi2Pd, we find that N(r) is governed by a length scale ξH=φ0/2πH, which decreases in rising fields. The vortex core size C, defined via the slope of the order parameter at the vortex center, C (dΔ/dr|r→0)-1, differs from ξH by a material dependent numerical factor. The new data on the tunneling conductance and…
Optical near-field microscopy of light focusing through a photonic crystal flat lens
2008
We report here the direct observation by using a scanning near-field microscopy technique of the light focusing through a photonic crystal flat lens designed and fabricated to operate at optical frequencies. The lens is fabricated using a III-V semiconductor slab, and we directly visualize the propagation of the electromagnetic waves by using a scanning near-field optical microscope. We directly evidence spatially, as well as spectrally, the focusing operating regime of the lens. At last, in light of the experimental scanning near-field optical microscope pictures, we discuss the lens ability to focus light at a subwavelength scale.
NC-AFM contrast formation on the calcite ($10\bar {1}4$) surface
2012
Calcite, the most stable polymorph of calcium carbonate, is one of the most abundant simple salts in the geological environment. Consequently, its natural cleavage plane has been studied extensively by a wide range of surface-sensitive techniques, giving indications for two reconstructions, namely a (2 × 1) and a so-called ‘row-pairing’ reconstruction. The existence of the (2 × 1) reconstruction has been discussed controversially in the literature, but is now confirmed as a true surface property. In contrast, a comprehensive discussion on the existence of the row-pairing reconstruction is lacking so far.Here, we present a non-contact atomic force microscopy (NC-AFM) study of the calcite s…
Measurements of SiO2glass surface parameters by methods of microscopy
2012
In this research we compare chemical and plasma treatment methods for surface of SiO2 glass. For chemical treatment of surface tequila and alcohol were used but for plasma treatment - Ar+As and Ar+Se plasmas. Surface topography was analyzed using atomic force microscope. Comparison of chemical and plasma treatment methods shows that surface treated with plasma is smoother. Because of their various chemical compositions tequila and alcohol show different results.
Failure Analysis of a Humeral Shaft Locking Compression Plate—Surface Investigation and Simulation by Finite Element Method
2019
A case study of a failed humeral shaft locking compression plate is presented, starting with a clinical case where failure occurred and an implant replacement was required. This study uses finite element method (FEM) in order to determine the failure modes for the clinical case. Four loading scenarios that simulate daily life activities were considered for determining the stress distribution in a humeral shaft locking compression plate (LCP). Referring to the simulation results, the failure analysis was performed on the explant. Using fracture surface investigation methods, stereomicroscopy and scanning electron microscopy (SEM), a mixed mode failure was determined. An initial fatigue failu…
Temperature dependence of surface reorganization characteristics of amphiphilic block copolymer in air and in water studied by scanning force microsc…
2015
We have investigated the surface reorganization characteristics of a novel amphiphilic diblock copolymer, poly(acetic acid-2-(2-(4-vinyl-phenoxy)-ethoxy)-ethylester)-block-polystyrene (PAEES-b-PS), in response to varying interfaces from air to water and vice-versa at various temperatures. The surface reorganization characteristics of the block copolymer films was monitored by scanning force microscopy, in order to delineate the kinetically controlled morphological process of surface reorganization of a diblock copolymer, with a particular emphasis on the phase contrast signal which allowed the determination of local composition patterns of PAEES-b-PS at the surface. Upon heating a water-an…
Characterization of the Microshell Surface Using Holography
2011
AbstractTo characterize the shape, the quality, and the roughness of microshells, digital holographic microscopy technology is used because it offers an appropriate ability to these studies. It captures holograms to reconstruct a double image, one for the intensity and another one for the phase. Using rotation axis, bump counting for the complete microshell surface is possible with a very high speed. Using image stitching and three-dimensional surface rebuilding software, mapping can be done in a few minutes. Each bump can then be characterized on the map by its position, diameter, and height.
Quantitative description of C-60 diffusion on an insulating surface
2010
The diffusion of ${\text{C}}_{60}$ molecules on large, atomically flat terraces of the ${\text{CaF}}_{2}(111)$ surface is studied under ultrahigh vacuum conditions at various substrate temperatures below room temperature. The weak molecule-substrate interaction on this insulating surface makes a direct observation of hopping events difficult. Therefore, to determine a quantitative value of the diffusion barrier, we employ the so-called onset method. This method is based on the analysis of spatial properties of islands created by nucleation of diffusing ${\text{C}}_{60}$ molecules, as measured by noncontact atomic force microscopy. We first determine the critical cluster size to be ${i}^{\en…
Quantitative atomic force microscopy
2017
A variety of atomic force microscopy (AFM) modes is employed in the field of surface science. The most prominent AFM modes include the amplitude modulation (AM) and the frequency modulation (FM) mode. Over the years, different ways for analyzing data acquired with different AFM modes have been developed, where each analysis is usually based on mode-specific assumptions and approximations. Checking the validity of the seemingly different approximations employed in the various analysis methods can be a tedious task. Moreover, a straightforward comparison of data analyzed with different methods can, therefore, be challenging. Here, we combine the existing evaluation methods which have been sep…