Projectively Equivariant Symbol Calculus

The spaces of linear differential operators acting on -densities on and the space of functions on which are polynomial on the fibers are not isomorphic as modules over the Lie algebra Vect (ⁿ) of vector fields of ⁿ. However, these modules are isomorphic as sl(n + 1,)-modules where is the Lie algebra of infinitesimal projective transformations. In addition, such an -equivariant bijection is unique (up to normalization). This leads to a notion of projectively equivariant quantization and symbol calculus for a manifold endowed with a (flat) projective structure. We apply the -equivariant symbol map to study the of kth-order linear differential operators acting on -densities, for an arbitrary manifold M and classify the quotient-modules .     

Photoelectric properties of In/p-(Cu, Ag)Ga(Se, Te)2 surface-barrier structures

Based on single crystals of AgGaSe₂, AgGaTe₂, CuGaTe₂ of the p-type, surface-barrier structures were manufactured by vacuum thermal deposition on illumination of which the photovoltaic effect was observed. It is established that the longwave edge of the photosensitivity of such structures possesses several inflections attributable to photoactive absorption involving paracipation of levels of lattice defects. It is shown that In/p-(Cu, Ag)Ga(Se, Te)₂ surface-barrier structures can be used as wide-band transducers and photoanalyzers of linearily polarized radiation. Translated from Zhurrnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 141–144, January–February, 1999.     

含缺陷的二维CuI光电性质的第一性原理计算

基于密度泛函理论计算了本征缺陷时二维CuI的光电特性,分析了能带结构以及复介电函数.本征2D CuI的带隙值为1.56 eV,为直接带隙半导体;I和Cu缺陷的引入使2D CuI的带隙值小,Cu缺陷的引入并未改变2D CuI的带隙方式,而I缺陷的引入使2D CuI变为间接带隙半导体.光学性质计算结果表明本征2D CuI的静介电函数为2.47, I缺陷的引入对2D CuI的静介电函数影响较小,但是在Cu缺陷时2D CuI的静介电函数急剧增大.     

Effect of oxygen on regulation of properties of moderately boron-doped diamond films

Regulation of oxygen on properties of moderately boron-doped diamond films is fully investigated. Results show that, with adding a small amount of oxygen (oxygen-to-carbon ratio < 5.0%), the crystal quality of diamond is improved, and a suppression effect of residual nitrogen is observed. With increasing ratio of O/C from 2.5% to 20.0%, the hole concentration is firstly increased then reduced. This change of hole concentration is also explained. Moreover, the results of Hall effect measurement with temperatures from 300 K to 825 K show that, with adding a small amount of oxygen, boron and oxygen complex structures (especially B₃O and B₄O) are formed and exhibit as shallow donor in diamond, which results in increase of donor concentration. With further increase of ratio of O/C, the inhibitory behaviors of oxygen on boron leads to decrease of acceptor concentration (the optical emission spectroscopy has shown that it is decreased with ratio of O/C more than 10.0%). This work demonstrates that oxygen-doping induced increasement of the crystalline and surface quality could be restored by the co-doping with oxygen. The technique could achieve boron-doped diamond films with both high quality and acceptable hole concentration, which is applicable to electronic level of usage.     

用相图原理研究玻璃结构和性质 (Ⅱ)核磁共振谱研究锂硼硅、镉硼锗和锂硼碲玻璃结构

本文在以前工作的基础上,用电子计算机计算了Li_2O-B_2O_3-SiO_2,CdO-B_2O_3-GeO_2和Li_2O一B_2O_3-TeO_2三元玻璃系统的NMR数据(N_(BO_4)),和实验结果相比较,根据相图原理,提出了一种新的玻璃结构模型,即相图模型.作者认为:玻璃和晶体具有相似的结构,多成分玻璃则是由相图中最邻近的同成分熔融化合物组成的混合物,且各化合物的量可按“杠杆原理”计算,即相图模型.对于未知相图的三元系统,在相图模型的基础上,作者作了一些简单的假设并进行修正.     

Photo‐capacitance spectroscopy investigation of deep‐level defects in AlGaN/GaN hetero‐structures with different current collapses

We have investigated electronic deep levels in two AlGaN/GaN hetero‐structures with different current collapses grown at 1150 and 1100 °C by a photo‐capacitance spectroscopy technique, using Schottky barrier diodes. Three specific deep levels located at ～2.07, ～2.80, and ～3.23 eV below the conduction band were found to be significantly enhanced for severe current collapse, being in reasonable agreement with photoluminescence and capacitance–voltage characteristics. These levels probably originate in Ga vacancies and residual C impurities and are probably responsible for the current collapse phenomena of the AlGaN/GaN hetero‐structures. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sub-diffraction-limited far-field imaging in infrared

We investigated a far-field superlens operating at mid-infrared wavelength that allows resolving subwavelength features in the far-field. By utilizing evanescent enhancement provided by surface plasmon excitation of silver nanorods and Moiré effect, we numerically demonstrated that subwavelength information of an object can be converted to propagating information. This information can then be captured by conventional optical components. A simple image reconstruction algorithm can restore the subwavelength object. A sub-diffraction-limited resolution of 2.5 μm at 6-μm wavelength is demonstrated.     

Flat Complex Vector Bundles,the Beltrami Differential and W-Algebras

Since the appearance of the paper by Bilal et al. in 1991, it has been widely assumed that W-algebras originating from the Hamiltonian reduction of an SL(n,C)-bundle over a Riemann surface give rise to a flat connection, in which the Beltrami differential may be identified. In this Letter, it is shown that the use of the Beltrami parametrization of complex structures on a compact Riemann surface over which flat complex vector bundles are considered, allows the construction of the above mentioned flat connection. It is stressed that the modulus of the Beltrami differential is of necessity less than one, and that solutions of the so-called Beltrami equation give rise to an orientation-preserving smooth change of local complex coordinates. In particular, the latter yields a smooth equivalence between flat complex vector bundles. The role of smooth diffeomorphisms which induce equivalent complex structures is specially emphasized. Furthermore, it is shown that, while the construction given here applies to the special case of the Virasoro algebra, the extension to flat complex vector bundles of arbitrary rank does not provide generalizations of the Beltrami differential usually considered as central objects for such non-linear symmetries.