ON THE FORMATION OF THE SBGA HETEROANTISITE IN METALORGANIC VAPOR-PHASE EPITAXIAL GAAS-SB

Metalorganic vapor-phase epitaxial growth of GaAs doped with isovalent Sb is reported. By increasing the trimethylantimony concentration during growth the total Sb concentration was varied between 1 X 10(17)-1 X 10(19) cm-3. A new deep level defect with an activation energy of the thermal emission rates of E(c) - 0.54 eV is observed. The defect concentration increases with increasing As partial pressure and with increasing Sb doping. It is also found that the EL2 concentration decreases with increasing Sb doping. The new energy level is suggested to be the 0/ + transition of the Sb(Ga) heteroantisite defect. No photocapacitance quenching effect, reflecting a metastable state as seen for EL2 (As(Ga)), is observed for Sb(Ga).

Formation of the Yazi Spring Stream and its significance on tectonics-climate on the northern slope of Kunlun Mountains

IEECAS SKLLQG

Formation of the V center on H-type zeolites with thermal treatment

The effect of thermal treatment on H-MCM-22 and H-ZSM-5 zeolites was investigated using the electron spin resonance technique. A six-line signal (denoted as A, g = 2.048, A = 22. 15 G) was detected on H-MCM-22 after He purging at high temperatures, whose intensities increased with the treating temperature. The same signal was also found on H-ZSM-5 zeolites with different crystal sizes. The paramagnetic center was identified as a V center, namely, a hole of an electron trapped on an oxygen atom bonding to a nearby aluminum atom. These signals appeared only on a dealuminated sample or a sample concomitantly with dealumination. The formation of the hole might involve an electron transferring from the lattice oxygen to a nonframework aluminum species, and the hyperfine splitting is caused by the interaction between the electron hole locating on the p orbit of oxygen and the framework aluminum bonding with the oxygen. The signal disappeared after the sample was exposed to air or oxygen at room temperature. However, the process was reversible. A new set of signals (denoted as B, g(1) = 2.008, g(2) = 2.003, g(3) = 1.9985) was observed after oxygen adsorption on the H-MCM-22 pretreated with He at 973 K or He purging at 973 K on the H-MCM-22 pretreated with oxygen at 813 K, which was attributed to the O- species.

Formation of nanogratings on the surface of a ZnSe crystal irradiated by femtosecond laser pulses

Two collinear femtosecond laser pulses, one at wavelength of 800 nm and the other at 400 nm (double frequency), simultaneously irradiated the surface of ZnSe crystal, which resulted in regular nanograting with period of 180 nm on the whole ablation area. We attribute the formation of the nanograting to be due to the interference between the surface scattered wave of 800 nm lasers and the 400 nm light. The period of the nanograting Lambda is about lambda/2n, where n is refractive index of the sample, and lambda, the laser wavelength. This mechanism is supported by observation of rotation of the nanograting with the polarization of 400 nm light, and by the dependence of Lambda similar to lambda of the nanoripples on the surface of semiconductors and dielectrics.

Effect of Shear Flow on the Formation of Ring-Shaped ABA Amphiphilic Triblock Copolymer Micelles

We have investigated the effect of Shear flow on the formation of rill.-shaped ABA triblock copolymer (P4VP(43)-b-PS260-b-P4VP(43)) micelles. The results reveal that Shear flow Plays an important role in the formation of the rings Both ring size and its, distribution are found to be dependent sensitively on the stirring rate. Sizable rings are more likely to be formed at moderate stirring rate, Interestingly, the ring formation mechanism is also dependent oil the Shear flow. Copolymers are likely to form rings via end-to-end cylinder connection at low stirring rates, whereas they tend to form rings via the pathway of the rod-sphere-vesicle-ring it high stirring rates.

A Study of the Tribological Behavior of Carbon-Nanotube-Reinforced Ultrahigh Molecular Weight Polyethylene Composites

The tribological properties of the high-strength and high-modulus ultrahigh molecular weight polyethylene (UHMWPE) film and the UHMWPE composites reinforced by multiwalled carbon nanotubes (MWCNT/UHMWPE) were investigated using a nanoindenter and atomic force microscope (AFM). The MWCNT/UHMWPE composites films exhibited not only high wear resistance but also a low friction coefficient compared to the pure UHMWPE films. We attribute the high wear resistance to the formation of the new microstructure in the composites due to the addition of MWCNTs.

Optimizations for the uniformity of the non-volatile volume grating in doubly doped LiNbO3 crystals

The formation of the non-uniformity of the non-volatile volume grating in doubly doped LiNbO3 crystals is studied in detail. We find that the non-uniformity of the grating is mainly caused by strong ultraviolet light absorption, and the average saturation space-charge field is small and the diffraction efficiency is low as a result of the non-uniformity of the grating. In order to optimize the uniformity of the grating, we propose the recording scheme by using two sensitizing beams simultaneously from the two opposite sides of the crystals. Theoretical simulations and experimental verifications are performed. Results show that the well uniformed grating with high diffraction efficiency can be obtained by using this optimization scheme. (c) 2004 Elsevier B.V. All rights reserved.

Formation of Fe-N films containing Fe6N2 phase by ion beam assisted deposition

Fe-N films were deposited on Si(100) and GaAs(100) substrates at room temperature by ion beam assisted deposition under various N/ Fe atomic arrival ratio, 0.09, 0.12, 0.15. The results of X-ray diffraction indicated that the film deposited at 0.12 of N/Fe arrival ratio contained a considerable fraction of the Fe16N2 phase which had grown predominantly in the [001] orientation. For the larger N/Fe arrival ratio, a martensite phase with 15 at.% nitrogen was obtained. It was found that a lower deposition temperature (<200 degrees C) was necessary for the formation of the Fe16N2 phase.