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排序方式: 共有107条查询结果,搜索用时 15 毫秒
91.
Edwin L.H. Mayes James G. Partridge Matthew R. Field Dougal G. McCulloch Steven M. Durbin Hyung-Suk Kim Martin W. Allen 《Physica B: Condensed Matter》2012,407(15):2867-2870
Oxidized iridium (IrOx) anodes fabricated on n-type ZnO single crystal wafers using reactive pulsed laser deposition are known to produce high quality Schottky barriers with ideality factors approaching the image-force-controlled limit for laterally homogeneous interfaces. These high performance IrOx/ZnO Schottky contacts were cross-sectioned and analyzed using transmission electron microscopy, revealing an amorphous interfacial layer of 2–3 nm thickness. Electron energy loss spectroscopy, used to study the composition of the interface region, showed evidence of significant zinc diffusion across the interface into the IrOx film, which leads to the creation of Zn vacancies (acceptors), in the ZnO sub-interface region. There is also evidence for oxygen passivation near the interface resulting from the use of an active oxygen ambient during the IrOx deposition. Both these factors may explain the outstanding electrical performance of these Schottky devices. 相似文献
92.
Ene reactions of suitably substituted olefins with dimethyl acetylenedicarboxylate give substituted 1,4-pentadiene-1,2-dicarboxylates, which undergo acid-catalyzed cyclization to α-carbomethoxymethylene γ-lactones. 相似文献
93.
94.
95.
D.P. Edwards D.G. McCulloch B.C. Muddle R.H.J. Hannink 《Micron (Oxford, England : 1993)》1994,25(6):617-621
The microstructure of a silicon nitride (Si3N4)-based ceramic, prepared by a process combining direct nitridation and reactive liquid phase sintering of silicon/ceramic oxide powder compacts, has been characterised using analytical transmission electron microscopy. The presence of the reactive liquid phase, promoted by the addition of oxides from the CaO-Al2O3-SiO2 ternary system, resulted in an as-fired microstructure containing a mixture of crystalline phases based on -Si3N4, β-Si3N4 and Si2 N2O, and distinct amorphous regions rich in Si, Al and Ca. X-ray microanalysis revealed the calcium to be wholly partitioned to the glassy phase, while significant concentrations of aluminium were detected in both β-Si3N4 and Si2N2O. The observed compositions of these phases, together with measured lattice parameters systematically in excess of those of the pure compounds, imply that they are in fact β- and O-sialons respectively. Semi-quantitative energy dispersive X-ray spectroscopy, using an ultra-thin window detector, is demonstrated to be capable of distinguishing clearly between these phases according to their oxygen content and of determining the aluminium content of both phases to within ± 1 equ.%, even at concentration levels of <5 equ.%. 相似文献
96.
Neil McCulloch Eitan Abraham 《Physica C: Superconductivity and its Applications》2009,469(21):1966-1969
The formation of bipolarons in the presence of magnetic impurities is studied theoretically. We use the extended Hubbard Su–Schrieffer–Heeger (SSH) model with Brazovskii–Kirova and Kondo interaction terms. Parameters are chosen suitably for cis-polyacetylene. A Quantum Monte Carlo (QMC) algorithm is used to study the equilibrium lattice structure and charge distribution as a function of doping level and Kondo exchange integral. The magnetic impurities can have a destructive effect on bipolaron stability, instead favouring the two polaron configuration. However by suitably adjusting the doping level, bipolarons can be stabilized over a wide range of impurity strength. 相似文献
97.
M. R. Field J. G. Partridge J. du Plessis D. G. McCulloch 《Applied Physics A: Materials Science & Processing》2009,97(3):627-633
The electrical and structural characteristics of hafnium oxide thin films reactively deposited from a filtered cathodic vacuum
arc have been investigated. X-ray photoelectron spectroscopy was used to determine the deposition conditions (Ar/O2 ratio) which produced stoichiometric HfO2 films. Cross-sectional transmission electron microscopy showed that the micro-structure of the films was highly disordered
with electron-diffraction analysis providing evidence for the presence of sub-nano-metre crystallites of the monoclinic HfO2 (P21/c) phase. Further evidence for the presence of this phase was provided by measuring the O k-edge using electron energy loss spectroscopy and comparing it with calculations performed using FEFF8.2, a multiple scattering
code. Surface imaging revealed that local film damage occurred in films deposited with substrate bias voltages exceeding −200 V.
The current-leakage characteristics of the HfO2 films deposited with a bias of approximately −100 V suggest that device grade HfO2 films can be produced from a filtered cathodic vacuum arc. 相似文献
98.
The Quantum cascade (QC) laser is an entirely new type of semiconductor device in which the laser wavelength depends on the band-gap engineering. It can be made to operate over a much larger range than lead salt lasers, covering significant parts of both the infrared and submillimetre regions, and with higher output power. In this tutorial review we survey some of the applications of these new lasers, which range from trace gas detection for atmospheric or medical purposes to sub-Doppler and time dependent non-linear spectroscopy. 相似文献
99.
Crouch DJ Skabara PJ Heeney M McCulloch I Coles SJ Hursthouse MB 《Chemical communications (Cambridge, England)》2005,(11):1465-1467
Rigidification has been achieved in thiophene-tetrafluorophenylene architectures through strong S...F and H...F intramolecular interactions; the resulting materials are promising candidates for p-type organic field effect transistors. 相似文献
100.
Dieckmann-type cyclization reactions have been employed in the synthesis of the alkyl substituted naphthoquinone 11 and the naphthalenes 10 and 12. Various conditions for the benzylic oxidation of these compounds have been investigated with a view towards the synthesis of some naphthalene based natural products. 相似文献