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101.
L. Malikova Fred H. Pollak Oleg Gorea Alexander Korotcov 《Journal of Electronic Materials》2000,29(11):1346-1350
Using contactless electroreflectance (CER) and piezoreflectance at 300 K we have characterized a GaAs/GaAs1?xPx multiple quantum well (MQW) structure, “GaAs” (nominal) and GaAsP epilayers grown by chloride transport chemical vapor deposition on GaAs (001) substrates. From a detailed lineshape fit to the CER data from the epilayers we have determined the energies of the fundamental band gap and hence the phosphorous composition. The nominal “GaAs” epilayers were found to have phosphorous compositions of about 2.5–3.2%, a result of the phosphorous diffusion between growth chambers in the reactor. The GaAs1?xPx epilayer had x=0.29. For the GaAs0.97P0.03/GaAs0.71P0.29MQW comparison between the experimentally observed energies of a number of quantum transitions with a theoretical envelope function calculation, including the effects of strain in the barriers, made it possible to evaluate the unstrained conduction band offset parameter Qc=0.50±0.05. Our value for this parameter is discussed in relation to other works. Atomic force microscopy was employed to investigate the surface morphology of the 230 Å GaAsP top layer of the MQW in addition to a 2000 Å GaAsP epilayer. From the absence of any cross-hatch pattern associated with misfit dislocations on the former we concluded that the GaAsP in the MQW is pseudomorphic. On the other hand the 2000 Å epilayer exhibited signs of strain relaxation. 相似文献
102.
Victor Shelukhin David Ehre Etay Lavert Ellen Wachtel Yishay Feldman Alexander Tagantsev Igor Lubomirsky 《Advanced functional materials》2011,21(8):1403-1410
The magnitude and direction of the permanent electric polarization in the non‐crystalline, polar phase (termed quasi‐amorphous) of SrTiO3 in SiSiO2MeSrTiO3Me, (Me = Cr or W), SiSrRuO3SrTiO3, and SiSrTiO3 layered structures were investigated. Three potential sources of the polarization which appears after the material is pulled through a temperature gradient were considered: a) contact potential difference; b) a flexoelectric effect due to a strain gradient caused by substrate curvature; and c) a flexoelectric effect due to the thermally induced strain gradient that develops while pulling through the steep temperature gradient. Measurements show that options a) and b) can be eliminated from consideration. In most cases studied in this (SiSrTiO3, SiSiO2MeSrTiO3Me, M = Cr or W) and previous works (SiBaTiO3, SiBaZrO3), the top surface of the quasi‐amorphous phase acquires a negative charge upon heating. However, in SiSrRuO3SrTiO3 structures the top surface acquires a positive charge upon heating. On the basis of the difference in the measured expansion of the upper and lower surfaces of the SrTiO3 layer in the presence and absence of SrRuO3, we contend that the magnitude and direction of the pyroelectric effect are determined by the out‐of‐plane gradient of the in‐plane strain in the SrTiO3 layer while pulling through the temperature gradient. 相似文献
103.
Schwaighofer A Tresp V Mayer P Krause A Beuthan J Rost H Metzger G Müller GA Scheel AK 《IEEE transactions on bio-medical engineering》2003,50(3):375-382
We describe a classification system for a novel imaging method for arthritic finger joints. The basis of this system is a laser imaging technique which is sensitive to the optical characteristics of finger joint tissue. From the laser images acquired at baseline and follow-up, finger joints can automatically be classified according to whether the inflammatory status has improved or worsened. To perform the classification task, various linear and kernel-based systems were implemented and their performances were compared. Based on the results presented in this paper, we conclude that the laser-based imaging permits a reliable classification of pathological finger joints, making it a sensitive method for detecting arthritic changes. 相似文献
104.
Alexander Usenko 《Journal of Electronic Materials》2003,32(8):872-876
We observe hydrogen platelet buildup in single-crystalline silicon caused by hydrogen-plasma processing. The platelets are
aligned along a layer of lattice defects formed in silicon before the plasma processing. The buried-defect layer is formed
by either silicon-into-silicon or argon-into-silicon implantation. We discuss the platelet nucleation, growth, and merge phenomena
and discuss applicability of the plasma hydrogenation to silicon-on-insulator (SOI) wafer fabrication by layer transfer. 相似文献
105.
Alexander E.Braun 《集成电路应用》2006,(5):25-25
涉足尖端技术研究工作的芯片制造商正在把无数新材料和奇特的器件结构结合起来,用于65nm及更低节点的量产。同时他们发现,在这些研究上的努力生产的结果还包括目前必须着手解决各器件各个层上出现的 相似文献
106.
Mario Huemer Christian Hofbauer Alexander Onic Johannes B. Huber 《AEUE-International Journal of Electronics and Communications》2014,68(10):958-968
Unique word-orthogonal frequency division multiplexing (UW-OFDM) is a novel signaling concept where the guard interval is implemented as a deterministic sequence, the so-called unique word. The UW is generated by introducing a certain level of redundancy in the frequency domain. Different data estimation strategies and the favourable bit error ratio (BER) performance of UW-OFDM, as well as comparisons to competing concepts have already extensively been discussed in previous papers. This work focuses on the different possibilities on how to generate UW-OFDM signals. The optimality of the two-step over the direct approach in systematic UW-OFDM is proved analytically, we present a heuristic algorithm that allows a fast numerical optimization of the redundant subcarrier positions, and we show that our original intuitive approach of spreading the redundant subcarriers in systematically encoded UW-OFDM by minimizing the mean redundant energy is practically also optimum w.r.t. transceiver based cost functions. Finally, we derive closed form approximations of the statistical symbol distributions on individual subcarriers as well as the redundant energy distribution and compare them with numerically found results. 相似文献
107.
Gen He Ning Hu Alexander M. Xu Xiangling Li Yunlong Zhao Xi Xie 《Advanced functional materials》2020,30(21)
Establishing techniques to efficiently and nondestructively access the intracellular milieu is essential for many biomedical and scientific applications, ranging from drug delivery, to electrical recording, to biochemical detection. Cell penetration using nanoneedle arrays is currently a research focus area because it not only meets the increasing therapeutic demands of cell modifications and genome editing, but also provides an ideal platform for tracking long‐term intracellular information. Although the precise mechanism driving membrane penetration by nanoneedle arrays is still unclear, the low cytotoxicity, wide range of delivered materials, diverse cell type targets, and simple material structures of nanoneedle arrays make these splendid platforms for cell access. Here, the recent progress in this field is reviewed by examining device architectures and discussing mechanisms for nanoneedle penetration, and the major studies demonstrating the most general applicability of nanoneedle arrays, typical methodologies to access the intracellular environment using nanoneedles with spontaneous or assisted penetration modes, as well as biosafety aspects are presented. This review should be valuable for deeply understanding the materials fabrication principles, device designs, cell penetration methodologies, biosafety aspects, and application strategies of nanoneedle array‐based systems that are of crucial importance for the development of future practical biomedical platforms. 相似文献
108.
Alessandra Di Gaspare Eva Arianna Aurelia Pogna Luca Salemi Osman Balci Alisson Ronieri Cadore Sachin Maruti Shinde Lianhe Li Cinzia di Franco Alexander Giles Davies Edmund Harold Linfield Andrea Carlo Ferrari Gaetano Scamarcio Miriam Serena Vitiello 《Advanced functional materials》2021,31(10):2008039
An electrically switchable graphene terahertz (THz) modulator with a tunable-by-design optical bandwidth is presented and it is exploited to compensate the cavity dispersion of a quantum cascade laser (QCL). Electrostatic gating is achieved by a metal grating used as a gate electrode, with an HfO2/AlOx gate dielectric on top. This is patterned on a polyimide layer, which acts as a quarter wave resonance cavity, coupled with an Au reflector underneath. The authors achieve 90% modulation depth of the intensity, combined with a 20 kHz electrical bandwidth in the 1.9–2.7 THz range. The modulator is then integrated with a multimode THz QCL. By adjusting the modulator operational bandwidth, the authors demonstrate that the graphene modulator can partially compensate the QCL cavity dispersion, resulting in an integrated laser behaving as a stable frequency comb over 35% of the operational range, with 98 equidistant optical modes and a spectral coverage ~1.2 THz. This paves the way for applications in the terahertz, such as tunable transformation-optics devices, active photonic components, adaptive and quantum optics, and metrological tools for spectroscopy at THz frequencies. 相似文献
109.
Dmitry V. Averyanov Ivan S. Sokolov Igor A. Karateev Alexander N. Taldenkov Oleg E. Parfenov Andrey M. Tokmachev Vyacheslav G. Storchak 《Advanced functional materials》2021,31(18):2010269
Integration of crystalline oxides with silicon provides a versatile platform to extend and advance silicon technology. The interface between oxide and Si controls the structure and functional properties of the resulting material. In particular, the formation of a submonolayer metal phase on silicon is the standard approach to stabilize the epitaxial growth of oxides. However, fundamental questions—a) whether the interface transforms in the process of the synthesis; and b) if it is possible to control the interface and its electronic structure by varying the submonolayer template—remain unanswered. The present study employs MBE synthesis of EuO and SrO on Si(001) to demonstrate that the structure of the oxide/Si interface does not depend on the type of the template, its symmetry, and stoichiometry. Chemical transformations of the templates converging into the same 2D product are detected in situ by electron diffraction. Then, the common interfacial structure of 1D periodicity is visualized by high-resolution electron microscopy. The study provides insights into the process of oxide integration with silicon but also sets the limits in designing oxide/Si interfaces. 相似文献
110.
Photo‐Induced Functionalization of Spherical and Planar Surfaces via Caged Thioaldehyde End‐Functional Polymers 下载免费PDF全文
Michael Kaupp Alexander S. Quick Cesar Rodriguez‐Emmenegger Alexander Welle Vanessa Trouillet Ognen Pop‐Georgievski Martin Wegener Christopher Barner‐Kowollik 《Advanced functional materials》2014,24(36):5649-5661
The synthesis and application of a novel reversible addition‐fragmentation chain transfer (RAFT) agent carrying a photocaged thioaldehyde moiety is described (λmax = 355 nm). RAFT polymerization of styrene, dimethylacrylamide and a glycomonomer is evidenced (3600 g mol?1 ≤ Mn ≤ 15 000 g mol?1; 1.07 ≤ ? ≤ 1.20) with excellent end‐group fidelity. The photogenerated thioaldehyde on the chain ends can undergo hetero Diels–Alder reactions with dienes as well as reactions with nucleophiles. The terminal photoreactive polymers are photografted to porous diene‐reactive polymeric microspheres. The grafted particles are in‐depth characterized via scanning electron microscopy, elemental analysis, X‐ray photoelectron spectroscopy, and high resolution FT‐IR microscopy, leading to a qualitative as well as quantitative image of the core–shell objects. Grafting densities up to 0.10 molecules nm?2 are reached. The versatility of the thioaldehyde ligation is evidenced by spatially resolved grafting of polystyrene onto nucleophilic groups present in poly (dopamine) (PDA)‐coated glass slides and silicon wafers via two‐photon direct laser writing (DLW) imaged by ToF‐SIMS. The combination of thioaldehyde ligation, RAFT polymerization, and DLW allows for the spatially resolved grafting of a vast range of polymers onto various substrates in any desired pattern with sub‐micrometer resolution. 相似文献