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951.
It has been shown that the radiation spectrum of implanted α-SiC p-n structures depends on the heat treatment temperature. The radiative intensity of green and IR peaks varies with the increase of the heat treatment temperature: at the minimum temperature the IR peak is dominating, while at the maximum temperature the green line is dominant. In this case the IR line disappears practically completely. The presence of green luminescence seems to be attributed to radiative recombination at donor-acceptor pairs. The IR luminescence line should be ascribed to the radiative recombination at deep (~1.5 eV) levels produced during ion implantation. 相似文献
952.
M. L. Abel K. Shimizu M. Holliman J. F. Watts 《Surface and interface analysis : SIA》2009,41(4):265-268
Peak‐fitting has been performed on a series of peaks obtained by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) analysis in order to assess whether information may be obtained from this procedure on the samples' characteristics. A variety of samples were examined including a range of treatments for aluminium leading to different surface roughnesses, polymer films with a range of polydispersities, molecular weight (MW) and thicknesses as well as aluminium samples with adsorbed adhesion promoters on the surface. Variation of peak‐fitting was assessed by varying the peak intensity, full width at half maximum (FWHM) and peak asymmetry. Although further studies are needed it is possible to say that the peak width increases with roughness whereas peak asymmetry seems to be related to oxide thickness. Polymer characteristics do not seem to influence the width whereas the peak asymmetry increases either versus MW or polydispersity. A possible assumption is that the peak asymmetry relates to the ion formation processes. Additional work with varying polymer films thickness indicates that both FWHM and peak asymmetry may be related to sample charging and this could be used for assessment of film thicknesses. Finally, peak‐fitting was used to obtain a more reliable peak area when peaks are too close in mass to use current methods. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
953.
Mao‐Suan Huang Yuh‐Chyun Chiang Sheng‐Chieh Lin Hsin‐Chung Cheng Chiung‐Fang Huang Yung‐Kang Shen Yi Lin 《先进技术聚合物》2012,23(1):57-64
This study develops an improved method for generating aluminum mold inserts used in the replication of polymer‐based microfluidic chip. Since molding masters that are suitable for microfluidic chip replication must have features whose dimensions are of the order of tens to hundreds of microns, micro electrical discharge machining is employed herein to fabricate an aluminum mold insert of a microfluidic chip. The width and depth of the aluminum mold insert for the microfluidic chip are 61.50 and 49.61 µm, respectively. The surface roughness values of the microchannel and the sample reservoir in aluminum mold insert for the microfluidic chip are 53.9 and 34.3 nm, respectively. PMMA material is adopted as the molded microfluidic chip that is produced by micro‐hot embossing molding. The PMMA material can replicate the microchannel and sample reservoir very well when the aluminum mold insert is used in micro‐hot embossing molding. The results indicate that the most important parameter in the replication of molded microfluidic chip is the embossing pressure, which is also the most important parameter in determining the surface roughness of the molded microfluidic chip. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
954.
为了对KBA显微镜的分辨能力进行准确计算,对KBA显微镜的分辨力和影响因素进行了研究,分析了衍射效应、几何像差、面形误差和粗糙度等因素对分辨力的影响,以此为基础建立了KBA显微镜的分辨力计算模型,并模拟了KBA显微镜的分辨力与视场的关系。用KBA显微镜获得了2.5 keV能量的X射线成像结果,中心视场范围的分辨力约为6 m。通过实验结果与模型模拟的对比,可得建立的模型对KBA显微镜分辨力与视场尺寸的关系的描述与实际测试的结果基本符合,并对不完善之处进行了分析。 相似文献
955.
956.
Oscillatory sliding contact between a rigid rough surface and an elastic–plastic half-space is examined in the context of numerical simulations. Stick-slip at asperity contacts is included in the analysis in the form of a modified Mindlin theory. Two friction force components are considered – adhesion (depending on the real area of contact, shear strength and interfacial adhesive strength) and plowing (accounting for the deformation resistance of the plastically deformed half-space). Multi-scale surface roughness is described by fractal geometry, whereas the interfacial adhesive strength is represented by a floating parameter that varies between zero (adhesionless surfaces) and one (perfectly adhered surfaces). The effects of surface roughness, apparent contact pressure, oscillation amplitude, elastic–plastic properties of the half-space and interfacial adhesion on contact deformation are interpreted in the light of numerical results of the energy dissipation, maximum tangential (friction) force and slip index. A non-monotonic trend of the energy dissipation and maximum tangential force is observed with increasing surface roughness, which is explained in terms of the evolution of the elastic and plastic fractions of truncated asperity contact areas. The decrease of energy dissipation with increasing apparent contact pressure is attributed to the increase of the elastic contact area fraction and the decrease of the slip index. For a half-space with fixed yield strength, a lower elastic modulus produces a higher tangential force, whereas a higher elastic modulus yields a higher slip index. These two competing effects lead to a non-monotonic dependence of the energy dissipation on the elastic modulus-to-yield strength ratio of the half-space. The effect of interfacial adhesion on the oscillatory contact behaviour is more pronounced for smoother surfaces because the majority of asperity contacts deform elastically and adhesion is the dominant friction mechanism. For rough surfaces, higher interfacial adhesion yields less energy dissipation because more asperity contacts exhibit partial slip. 相似文献
957.
958.
Méndez-Vilas A Donoso MG González-Carrasco JL González-Martín ML 《Colloids and surfaces. B, Biointerfaces》2006,53(2):157-166
Surface topography of polished and blasted samples of a Ti6Al4V biomaterial has been studied using an atomic force microscope. Surface RMS roughness and surface area have been measured at different scales, from 1 to 50 μm, while at distances below 10 μm the surface RMS roughness in both kinds of samples is not very different, this difference becomes significant at larger scanning sizes. This means that the surface roughness scale that could have a main role in cell adhesion varies depending on the size, shape and flexibility of participating cells. This consideration suggests that in cell–material interaction studies, surface roughness should not be considered as an absolute and independent property of the material, but should be measured at scales in the order of the cell sizes, at least if a microscopic interpretation of the influence of roughness on the adhesion is intended. The microscopic information is contrasted with that coming from a macroscopic approach obtained by contact angle measurements for polar and non-polar liquids whose surface tension is comprised in a broad range. Despite the very large differences of contact angles among liquids for each surface condition, a similar increase for the blasted surface with respect to the polished has been found. Interpretation of these results are in accordance with the microscopic analysis done through the use of a functional roughness parameter, namely the valley fluid retention index, evaluated from the AFM images, which has been shown not to correlate with the RMS roughness, one of the most commonly used roughness parameter. 相似文献
959.
We studied topological effects of subcellular roughness displayed by a closely packed particle monolayer on adhesion and growth of endothelial cells. Poly(styrene-co-acrylamide) (SA) particles were prepared by soap-free emulsion copolymerization. Particle monolayers were prepared by Langmuir–Blodgett deposition using particles, which were 527 (SA053) and 1270 nm (SA127) in diameter. After 24-h incubation, cells tightly adhered on a tissue culture polystyrene dish and randomly spread. On the other hand, cells attached on particle monolayers were stretched into a narrow stalk-like shape. Lamellipodia spread from the leading edge of cells attached on SA053 monolayer to the top of the particles and gradually gathered to form clusters. This shows that cell–cell adhesion became stronger than cell–substrate interaction. Cells attached to SA127 monolayer extended to the reverse side of a particle monolayer and engulfed particles. They remained immobile without migration 24 h after incubation. This shows that the inhibition of extensions on SA127 monolayer could inhibit cell migration and cell proliferation. Cell growth on the particle monolayers was suppressed compared with a flat TCPS dish. The number of cells on SA053 gradually increased, whereas that on SA127 decreased with time. When the cell seeding density was increased to 200,000 cells cm−2, some adherent cells gradually became into contact with adjacent cells. F-actin condensations were formed at the frame of adherent cells and the thin filaments grew from the edges to connect each other with time. For the cell culture on SA053 monolayer, elongated cells showed a little alignment. Cells showed not arrangement of actin stress fibers but F-actin condensation at the contact regions with neighboring cells. Interestingly, the formed cell monolayer could be readily peeled from the particle monolayer. These results indicate that endothelial cells could recognize the surface roughness displayed by particle monolayers and the response was dependent on the pitch of particle monolayers. 相似文献
960.
Sharp JS Vader D Forrest JA Smith MI Khomenko M Dalnoki-Veress K 《The European physical journal. E, Soft matter》2006,19(4):423-432
Optical microscopy and atomic force microscopy were used to study a novel roughness-induced wrinkling instability in thin-film
bilayers of poly(ethylene oxide) (PEO) and polystyrene (PS). The observed wrinkling morphology is manifested as a periodic
undulation at the surface of the samples and occurs when the bilayers are heated above the melting temperature of the semi
crystalline PEO (Tm = 63
) layer. During the wrinkling of the glassy PS capping layers the system selects a characteristic wavelength that has the
largest amplitude growth rate. This initial wavelength is shown to increase monotonically with increasing thickness of the
PEO layer. We also show that for a given PEO film thickness, the wavelength can be varied independently by changing the thickness
of the PS capping layers. A model based upon a simple linear stability analysis was developed to analyse the data collected
for the PS and PEO film thickness dependences of the fastest growing wavelength in the system. The predictions of this theory
are that the strain induced in the PS layer caused by changes in the area of the PEO/PS interface during the melting of the
PEO are sufficient to drive the wrinkling instability. A consideration of the mechanical response of the PEO and PS layers
to the deformations caused by wrinkling then allows us to use this simple theory to predict the fastest growing wavelength
in the system. 相似文献