液相外延制备InGaAsP/InP掩埋异质结若干工艺问题的讨论

本文对InGaAsP/InP(DC-PBH)激光器掩埋异质结液相外延生长中的几个关键工艺问题进行了研究,提出了获得有利于沟道掩埋生长的理想沟道几何图形的新的腐蚀配方(Br_2/HBr),对二次外延再生长光刻腐蚀面损伤层和有害杂质的去除采用了阳极氧化工艺,同时探索了利用二次外延过程中Zn扩散来控制限制层(3)掺杂的新方法,在研究基础上制造了重现性好且性能良好的1.3μm激光二极管,室温时,阈值电流最低小于25mA,典型值为30mA,在60mA直流电流的驱动下,光输出功率高达12.5mW.     

二连通偶图的周长

本文给出了二连通偶图 G 的周长的下界的新的形式及 G 为哈密尔顿的新的充分条件.     

On the Semiclassical Propagator for Any One-Dimensional Admissible Potential

This paper shows that by choosing suitably the general fundamental invariantI=f(I₁) as a new canonical momentum, we can find the semiclassical propagator for any one-dimensional admissible potential, whereIis a certain function of the fundamental invariantI₁. We apply this method to the case of quartic potential and point out few applications of the propagator for this potential.     

Un modèle stochastique pour l'étude du bruit de fond dans un réacteur contrôlé par un dispositif de réglage automatique

Résumé On essaie de trouver l'équation du mouvement de la barre de contrôle d'un réacteur en théorie ponctuelle à un groupe de neutrons retardés à partir des principes stochastiques.     

Bornes quasi-inferieures et bornes superieures de la pression de ruine des coques de revolution par la methode des elements finis et par la programmation non-lineaire

This work is concerned with rigid-plastic limit analysis of shells of revolution subject to rotationally symmetric loadings. These shells, of arbitrary shape, are discretized into a series of finite elements, each being a conical shell. The von Mises condition, valid for sandwich shells, is used to compare the results obtained with existing values. After assembling the finite elements, the limit analysis program is reduced to a simple application of the non-linear programming technique where both the sequential unconstrained minimization technique (SUMT) and feasible conjugate direction (FCD) are utilized respectively for statically admissible and kinematically admissible approaches. Therefore, upper bounds and lower bounds of the collapse loads are found for some sample problems : conical, spherical, ellipsoidal, torispherical shells etc. These numerical results are illustrated and compared with existing ones described in the literature.     

Growth of Cu2S ultrathin nanowires in a binary surfactant solvent

We demonstrate a facile solution-phase method for the synthesis of single-crystal, high aspect ratio, and ultrathin nanowires of hexagonal-phase Cu2S by thermal decomposition of CuS2CNEt2 in a mixed surfactant solvent of dodecanethiol and oleic acid at 160 degrees C. Cu2S nanowires can be controllably synthesized with a diameter as thin as 1.7 nm and length up to tens of micrometers; they are usually aligned in the form of bundles with a thickness of hundreds of nanometers. Based on the experimental results, the formation mechanism of the ultrathin nanowires has been properly proposed. Some key synthetic parameters, which have a significant effect on the sizes and shapes of the products, have also been investigated in detail. UV-vis spectroscopy measurement reveals that the resultant ultrathin nanowires show a strong quantum size effect.     

Colorimetric and ratiometric fluorescent chemosensor with a large red-shift in emission: Cu(II)-only sensing by deprotonation of secondary amines as receptor conjugated to naphthalimide fluorophore

[reaction: see text] A new fluorescent probe N-butyl-4,5-di[2-(phenylamino)ethylamino]-1,8-naphthalimide 1 senses only Cu(II) among heavy and transition metal (HTM) ions by means of a colorimetric (primrose yellow to pink) method with a large red-shift in emission (green to red) attributed to the deprotonation of the secondary amines as a receptor conjugated to the naphthalimide fluorophore.     

Hydrothermal growth and optical properties of doughnut-shaped ZnO microparticles

Doughnut-shaped ZnO microparticles have been grown through a hydrothermal reaction in citrate solution at 120 degrees C. FESEM reveals that these microparticles consist of regular arranged nanoplates, and there is a concave on the surface of each microparticle. The existence of citrate is vital to the formation of the complex microparticles. Room temperature photoluminescence measurements show strong UV band emission. The yellow and green emissions related to the structure defects can be barely observed, indicating the high crystalline perfection of these microparticles.     

Body-centered-cubic Ni and its magnetic properties

The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52+/-0.08 micro(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs x cm(-3), as opposed to -5.7x10(4) ergs x cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation.