Adsorption, Segregation and Magnetization of a Single Mn Adatom on the GaAs (110) Surface

Density functional calculations with a large unit cell have been conducted to investigate adsorption, segregation and magnetization of Mn monomer on GaAs(110). The Mn adatom is rather mobile along the trench on GaAs(110), with an energy barrier of 0.56 eV. The energy barrier for segregation across the trenches is nevertheless very high, 1.67 eV. The plots of density of states display a wide gap in the majority spin channel, but show plenty of metal-induced gap states in the minority spin channel. The Mn atoms might be invisibl in scanning tunneling microscope (STM) images taken with small biases, due to the directional p-d hybridization. For example, one will more likely see two bright spots on Mn/GaAs(110), despite the fact that there is only one Mn adatom in the system

Ultraviolet photonic crystal laser

We fabricated two dimensional photonic crystal structures in zinc oxide films with focused ion beam etching. Lasing is realized in the near ultraviolet frequency at room temperature under optical pumping. From the measurement of lasing frequency and spatial profile of the lasing modes, as well as the photonic band structure calculation, we conclude that lasing occurs in the strongly localized defect modes near the edges of photonic band gap. These defect modes originate from the structure disorder unintentionally introduced during the fabrication process.Comment: 4 pages, 4 figure

Finite dimensional integrable Hamiltonian systems associated with DSI equation by Bargmann constraints

The Davey-Stewartson I equation is a typical integrable equation in 2+1 dimensions. Its Lax system being essentially in 1+1 dimensional form has been found through nonlinearization from 2+1 dimensions to 1+1 dimensions. In the present paper, this essentially 1+1 dimensional Lax system is further nonlinearized into 1+0 dimensional Hamiltonian systems by taking the Bargmann constraints. It is shown that the resulting 1+0 dimensional Hamiltonian systems are completely integrable in Liouville sense by finding a full set of integrals of motion and proving their functional independence.Comment: 10 pages, in LaTeX, to be published in J. Phys. Soc. Jpn. 70 (2001

Structural Equation Modeling Approach to Studying the Relationships among Safety Investment, Construction Employees’ Safety Cognition, and Behavioral Performance

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Self-optimization of optical confinement in ultraviolet photonic crystal slab laser

We studied numerically and experimentally the effects of structural disorder on the performance of ultraviolet photonic crystal slab lasers. Optical gain selectively amplifies the high-quality modes of the passive system. For these modes, the in-plane and out-of-plane leakage rates may be automatically balanced in the presence of disorder. The spontaneous optimization of in-plane and out-of-plane confinement of light in a photonic crystal slab may lead to a reduction of the lasing threshold.Comment: 5 pages, 5 figure

Broadband RCS Reduction of Microstrip Patch Antenna Using Bandstop Frequency Selective Surface

In this article, a simple and effective approach is presented to reduce the Radar Cross Section (RCS) of microstrip patch antenna in ultra broad frequency band. This approach substitutes a metallic ground plane of a conventional patch antenna with a hybrid ground consisting of bandstop Frequency Selective Surface (FSS) cells with partial metallic plane. To demonstrate the validity of the proposed approach, the influence of different ground planes on antenna’s performance is investigated. Thus, a patch antenna with miniaturized FSS cells is proposed. The results suggest that this antenna shows 3dB RCS reduction almost in the whole out-of operating band within 1-20GHz for wide incident angles when compared to conventional antenna, while its radiation characteristics are sustained simultaneously. The reasonable agreement between the measured and the simulated results verifies the efficiency of the proposed approach. Moreover, this approach doesn’t alter the lightweight, low-profile, easy conformal and easy manufacturing nature of the original antenna and can be extended to obtain low-RCS antennas with metallic planes in broadband that are quite suitable for the applications which are sensitive to the variation of frequencies

The Importance of Charge Redistribution during Electrochemical Reactions: A Density Functional Theory Study of Silver Orthophosphate (Ag3PO4)

The structural sensitivity of silver orthophosphate (Ag 3 PO 4 ) for photo-electrochemical water oxidation on (100), (110) and (111) surfaces has recently been reported by experimental studies (D. J. Martin et al., Energy Environ. Sci., 2013, 6, 3380-3386). The (111) surface showed the highest performance with an oxygen evolution rate of 10 times higher than the other surfaces. The high performance of the (111) surface was attributed to high hole mobility, high surface energy and, in a recent theoretical study (Z. Ma et al., RSC Adv., 2017, 7, 23994-24003), to a lower OH adsorption energy and the band structure. The investigations are based on a few structures and a full atomistic picture of the Ag 3 PO 4 under electrochemical reactions is still missing. Therefore, we report here a systematic study of the oxygen evolution reaction (OER) of Ag 3 PO 4 (100), (110), and (111) surfaces by density functional theory (DFT) calculations. Through a detailed investigation of the reaction energies and the overpotentials of OER on all possible surface orientations with all possible terminations and different involvement of Ag adsorption sites, we can confirm that (111) surfaces are highly active. However, surface orientation was not found to exclusively determine the electrochemical activity; neither did the number of Ag atoms involved in the adsorption of the intermediate species nor the type of surface termination or the different potential determining reaction steps. By using Bader charge analysis and investigation of the charge redistribution during OER, we found that the highest activity, i.e. lowest overpotential, is related to the charge redistribution of two OER steps, namely the O ad and the HOO ad formation. If the charge redistribution between these steps is small, then the overpotential is small and, hence, the activity is high. Charge redistributions are usually small for the (111) surface and therefore the (111) surface is usually the most active one. The concept of charge redistribution being decisive for the high activity of Ag 3 PO 4 may open a new design strategy for materials with highly efficient electrochemical surfaces.</p