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排序方式: 共有373条查询结果,搜索用时 15 毫秒
1.
2.
We investigated the morphological, structural and electronic properties of Pentacene thin films grown by vacuum thermal evaporation on different inert substrates at room temperature. The results of our AFM and STM analysis give an interplanar spacing of 1.54 nm corresponding to the (0 0 1) distance of the so-called “thin film phase”. The STS measurements show an HOMO-LUMO gap of 2.2 eV. 相似文献
3.
Oxide heterojunctions made of p-type La0.8Sr0.2MnO3 (LSMO) and niobium-doped n-type SrTiO3 (STO:Nb) have been fabricated by the pulsed laser deposition (PLD) technique and characterized under UV light irradiation by measuring the current-voltage, photovoltaic properties and the junction capacitance. It is shown that the heterojunctions work as an efficient UV photodiode, in which photogenerated holes in the STO:Nb substrate are injected to the LSMO film. The maximum surface hole density Q/e and external quantum efficiency γ are estimated to be 8.3×1012 cm−2 and 11% at room temperature, respectively. They are improved significantly in a p-i-n junction of LSMO/STO/STO:Nb, where Q/e and γ are 3.0×1013 cm−2 and 27%, respectively. 相似文献
4.
Choon-Woo Nahm 《Solid State Communications》2003,126(5):281-284
The microstructure, nonlinear properties, and stability against DC accelerated aging stress of ZnO-Pr6O11-CoO-based varistors doped with Er2O3 was investigated at sintering temperatures of 1300 and 1350 °C. The addition of Er2O3 to ZnO-Pr6O11-CoO-based varistor greatly improved the nonlinear properties and the varistor sintered at 1300 °C exhibited good nonlinearity, with nonlinear exponent of 52.8 and leakage current of 9.8 μA The increase of sintering temperature deteriorated the nonlinear properties, whereas it greatly improved the stability. 相似文献
5.
《The European Physical Journal A - Hadrons and Nuclei》2003,17(2):241-244
The helicity dependence of the γ
p↦pη reaction has been measured for the first time at a center-of-mass angle θ*
η = 70° in the photon energy range from 780 MeV to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4π-detector
system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. The helicity 3/2 cross-section
is found to be small and the results for helicity 1/2 agree with predictions from the MAID analysis.
Received: 19 December 2002 / Accepted: 10 March 2003 / Published online: 20 May 2003 相似文献
6.
The energy level alignment between C60 and Al has been investigated by using ultraviolet photoelectron spectroscopy. To obtain the interfacial electronic structure between C60 and Al, C60 was deposited on a clean Al substrate in a stepwise manner. The valence-band spectra were measured immediately after each step of C60 deposition without breaking the vacuum. The measured onset of the highest occupied molecular orbital energy level was located at 1.59 eV from the Fermi level of Al. The vacuum level was shifted 0.68 eV toward lower binding energy with additional C60 layers. The observed vacuum level shift means that the interface dipole exists at the interface between C60 and Al. The barrier height of electron injection from Al to C60 is 0.11 eV, which is smaller value than that of hole injection. 相似文献
7.
Thi Thanh-Tâm Nguyên Claude Delseth Jean-Pierre Kintzinger Pierre-Alain Carrupt Pierre Vogel 《Tetrahedron》1980,36(19):2793-2797
Natural-abundance 17O-NMR spectra of 7-oxanorbornane exo-3-oxatricyclo [3.2.1.02.4]octane and their unsaturated derivatives (endo cyclic and exocyclic double bonds) have been measured. Linear correlation laws were observed for of these ethers/corresponding hydrocarbons. The “cyclization shifts” for δo in ethers were not correlated by the “cyclization shifts” for δc of the corresponding hydrocarbons. 相似文献
8.
Fabian Ebner Philipp Mainik Dr. Lutz Greb 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5120-5124
Structural constraint represents an attractive tool to modify p-block element properties without the need for unusual oxidation or valence states. The recently reported methyl-calix[4]pyrrolato aluminate established the effect of forcing a tetrahedral aluminum anion into a square-planar coordination mode. However, the generality of this structural motif and any consequence of ligand modification remained open. Herein, a systematic ligand screening was launched, and the class of square-planar aluminum anions was extended by two derivatives that differ in the meso-substitution at the calix[4]pyrrolato ligand. Strikingly, this modification provoked opposing trends in the preference for a Lewis acidic binding mode with σ-donors versus the aluminum-ligand cooperative binding mode with carbonyls. Insights into the origin of these counterintuitive experimental observations were provided by computation and bond analysis. Importantly, this rationale might allow to exploit mode-selective binding for catalytic rate control. 相似文献
9.
In 2001, J.-M. Le Bars disproved the zero-one law (that says that every sentence from a certain logic is either true asymptotically almost surely (a.a.s.), or false a.a.s.) for existential monadic second order sentences (EMSO) on undirected graphs. He proved that there exists an EMSO sentence ? such that does not converge as (here, the probability distribution is uniform over the set of all graphs on the labeled set of vertices ). In the same paper, he conjectured that, for EMSO sentences with 2 first order variables, the zero-one law holds. In this paper, we disprove this conjecture. 相似文献
10.
The effect of a thermal annealing treatment on the performance of bulk heterojunction photovoltaic cells based on poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) and fullerene (C60) composites is investigated. Upon thermal annealing at 120 °C, short-circuit current and power conversion efficiency (η) are more than tripled, while a sharp rise by eight times in and η is found for the device annealed at 200 °C. It is concluded that the improved phase separation between MEH-PPV and C60 leads to the enhancement of and η at 120 °C, while thermodynamic molecule arrangement at the higher temperature of ∼200 °C induces a significant increase in all photovoltaic parameters of composite devices except the open-circuit voltage . 相似文献