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291.
G. Fuhr T. Schnelle T. Müller H. Hitzler S. Monajembashi K.-O. Greulich 《Applied Physics A: Materials Science & Processing》1998,67(4):385-390
Received: 19 May 1998/Accepted: 28 May 1998 相似文献
292.
The structure and stability of Be6, Be, and Be clusters have been investigated at the B3LYP, B3PW91, and second‐order Møller–Plesset (MP2) levels of theory, along with the 6‐311G* basis set for neutral and cationic clusters and the 6‐311+G* basis set for anion clusters. CCSD(T)/6‐311+G* has also been used to calculate some neutral structure to find the most stable structure. Twelve Be6, six Be, and eight Be isomers are identified. The distortion octahedron structure, pentagonal pyramids structure, and trapezoidal bipyramid structure are found to be the most stable structure on the neutral, cationic, and anionic surface, respectively. They are in agreement with the results reported previously. Natural bond orbital (NBO) analysis, molecular orbital (MO) pictures, and the nucleus independent chemical shift (NICS) values suggest aromatic of the neutral and cationic clusters and antiaromatic of the anionic cluster. The multi‐center σ bonds and delocalized π bonds play important role in the bonding of the beryllium clusters. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
293.
Prof. Dr. Yafei Li Yunlong Liao Prof. Dr. Zhongfang Chen 《Angewandte Chemie (International ed. in English)》2014,53(28):7248-7252
The design of new materials is an important subject in order to attain new properties and applications, and it is of particular interest when some peculiar topological properties such as reduced dimensionality and rule‐breaking chemical bonding are involved. In this work, we designed a novel two‐dimensional (2D) inorganic material, namely Be2C monolayer, by comprehensive density functional theory (DFT) computations. In Be2C monolayer, each carbon atom binds to six Be atoms in an almost planar fashion, forming a quasi‐planar hexacoordinate carbon (phC) moiety. Be2C monolayer has good stability and is the lowest‐energy structure in 2D space confirmed by a global minima search based on the particle‐swarm optimization (PSO) method. As a semiconductor with a direct medium band gap, Be2C monolayer is promising for applications in electronics and optoelectronics. 相似文献
294.
Hybrid Pt-CdSe nanocomposite was fabricated by a two-step chemical route. Cadmium selenide (CdSe) quantum rods (QRs) were prepared by a one-pot approach with tunable size. After ligand exchange, CdSe QRs were loaded with monodisperse 1.9 nm Pt nanopaticles in aqueous solution. Transmission electron microscopy (TEM) revealed the morphology of the Pt-CdSe nanostructure, and the decreased photoluminescence (PL) intensity demonstrated that electron and hole separation can be enhanced after loading Pt on CdSe QRs. X-ray photoelectron energy spectrum (XPS) was applied to confirm the existence of Pt and detect the Pt mass concentration of 3%. 相似文献
295.
We propose to use the exciton coupling between electrons and holes in different quantum wells to reach a strong Coulomb drag effect. The drag has to be really strong below the Mott transition when the most of the carriers are bound in excitons. We suggest to use the exciton drag for fabrication of DC transformer. Preliminary estimates for Si/SiO2/Si structure give the Mott transition temperature of the order of 100 K. 相似文献
296.
Enhanced Field Emission from Well-Patterned Silicon Nanoporous Pillar Arrays 总被引:1,自引:0,他引:1
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The silicon nanoporous pillar array (Si-NPA) is synthesized by using hydrothermal etching method, and the electron field emission properties are studied. The results show that Si-NPA has a low turn-on field of 1.48 V/μm at the emission current of 0.1 μA and its field emission is relatively stable. The field emission enhancement of Si-NPA is believed to originate from its unique morphology and structure. Our finding demonstrates that the Si-NPA is a promising candidate material for field emission applications. 相似文献
297.
K.B. Lee P.J. ParbrookT. Wang J. BaiF. Ranalli R.J. AireyG. Hill 《Journal of Crystal Growth》2009,311(10):2857-2859
The effect of the AlGaN electron blocking layer (EBL) thickness on the electrical and optical properties of 310 nm AlGaN single quantum well (SQW) light-emitting diodes (LEDs) has been investigated. A large ideality factor extracted from the current–voltage (I–V) characteristics indicates that a tunneling mechanism dominates the carrier transport process in the LEDs. The ideality factor decreases with increasing EBL thickness suggesting that deep-level state assisted tunneling is reduced. In addition, the QW emission intensity is enhanced with the introduction of an EBL due to the reduction of electron overflow to the p-type layer. The QW emission intensity is sensitive to the EBL thickness. This is attributed to the reduction of electron tunneling to the p-type layer with an EBL. 相似文献
298.
J. Denschlag D. Cassettari A. Chenet S. Schneider J. Schmiedmayer 《Applied physics. B, Lasers and optics》1999,69(4):291-301
A large variety of trapping and guiding potentials can be designed by bringing cold atoms close to charged or current-carrying
material objects. Using a current-carrying wire we demonstrate how to build guides and traps for neutral atoms and using a
charged wire we study a 1/r
2 singularity. The simplicity and versatility of the principles demonstrated in our experiments will allow for miniaturization
and integration of atom optical elements into matter-wave quantum circuits.
Received: 13 December 1998 / Revised version: 8 July 1999 / Published online: 8 September 1999 相似文献
299.
Xiaoyun Zhang Changhua AnShutao Wang Zongxian WangDaohong Xia 《Journal of Crystal Growth》2009,311(14):3775-3780
In this paper, we developed a generalized and greener composite-surfactants-assisted-solvothermal process (CSSP) to produce colloidal nanoparticles of metal sulfides. X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS) revealed that single-molecular-layer type of MoS2 nanoparticles with diameter 6–10 nm were successfully synthesized. The molecular structure model of the capped MoS2 nanoparticles was suggested through further examination by infrared spectra. Hexagonal CdS nanocrystals with spherical, triangle, and hollow sphere shapes were controllably synthesized by varying the experimental conditions. A possible in-situ reduction–sulfidation mechanism was proposed for the formation of Ag2S nanocrystals, where the metal ions were reduced to metallic nanoparticles before the generation of sulfides. The obtained nanocrystals through this CSSP approach could provide the building blocks for the bottom-up approach to nanoscale fabrication in nanoscience and nanotechnology. 相似文献
300.
Y. Kimura Y. Kitahama K. Takazawa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):203-208
Experimental set-up for studying effects of a strong magnetic field on a structure and a decay dynamics of molecules, was
designed and constructed. A vacuum chamber, in which a molecular beam propagated, was mounted in a bore of a superconducting
magnet. Laser light crossed the molecular beam in the magnetic field and excited the molecules. Fragment or parent ions produced
through sequential decay processes, were extracted by an electric field parallel to the magnetic field and detected by a microchannel
plate. By measuring the time-of-flight from the photo-excitation to the ion-detection, a species of ions —mass and charge
state— was identified. A performance of the set-up was demonstrated using the resonance enhanced multiphoton ionization process
through the
X2Π-A2Σ+ transition of nitric oxide (NO) molecules. A mass resolution m/Δm ≥180±6 was obtained in the field up to 10 T. This was
the first successful result demonstrating the sufficient mass resolution obtained by the time-of-flight technique in the strong
magnetic field up to 10 T. Parent NO+ ions were selectively detected by the mass spectrometer and the ion current was measured as a function of the frequency of
the laser light. Rotational transition lines were measured with a sufficient S/N ratio in the field up to 10 T. 相似文献