Single Crystal Growth and Physical Property Characterization of Non-centrosymmetric Superconductor PbTaSe_2

We report on the single crystal growth and superconducting properties of PbTaSe2 with the non-centrosymmetric crystal structure. By using the chemicM vapor transport technique, centimeter-size single crystals are success- fully obtained. The measurement of temperature dependence of electricaJ resistivity p（T） in both normal and superconducting states indicates a quasi-two-dimensional electronic state in contrast to that of polycrystalline samples. Specific heat C（T） measurement reveals a bulk superconductivity with Tc ≈ 3.75K and a specific heat jump ratio of 1.42. All these results are in agreement with a moderately electron-phonon coupled, type-g Bardeen-Cooper-Schrieffer superconductor.

Fabrication and Piezoelectric Characterization of Single Crystalline GaN Nanobelts

GaN nanobelts are synthesized using the chemical vapor deposition method with the catalyst of Ni. The mi- crostrueture, composition and photoluminescence property are characterized by x-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy and photoluminescence spectra. The results demonstrate that the single crystalline GaN nanobelts are grown with a hexagonal wurtzite structure, in width ranging from 500nm to 2μm and length up to 10-20μm. Moreover, a large piezoelectric coefficient d33 of 20pm/V is obtained from GaN nanobelts by an atomic force microscopy and the high piezoelectric property implies that the perfect single crystallinity and the freedom of dislocation for the GaN nanobelt have significant impact on the electromechanical response.

The Single Valley Character of Level Degree Function

Strict proof has been given to single valley character of level degree function by use of convex analysis theory, which provides reliable theoretical basis for the optimization of the data processing with respect to level degree. As circle degree and cylindrical degree have the same mathematical structures, their single valley character can be proved by the same method.

Fabrication and Characterization of a Single Electron Transistor Based on a Silicon-on-Insulator

A single electron transistor based on a silicon-on-insulator is successfully fabricated with electron-beam nano- lithography, inductively coupled plasma etching, thermal oxidation and other techniques. The unique design of the pattern inversion is used, and the pattern is transferred to be negative in the electron-beam lithography step. The oxidation process is used to form the silicon oxide tunneling barriers, and to further reduce the effective size of the quantum dot. Combinations of these methods offer advantages of good size controllability and accuracy, high reproducibility, low cost, large-area contacts, allowing batch fabrication of single electron transistors and good integration with a radio-frequency tank circuit. The fabricated single electron transistor with a quantum dot about 50nto in diameter is demonstrated to operate at temperatures up to 70K. The charging energy of the Coulomb island is about 12.5meV.

Thermo-optic characterization of KDP single crystals by a modified Snarmont setup for electro-optic modulation system

For our KDP crystal orientation, various tbermo-optic （TO） and relevant temperature-dependence param- eters are defined, presented, and studied in the framework of a transverse and a longitudinal electro-optic （EO） modulation systems. This study is based on the concept of the so-called opto-electrical bias （~） ap- plied to the system. For both of the above EO-modulation systems, a set of original equations is extracted and investigated with regard to each of the more important TO or temperature coefficients. Using these equations, for these parameters the role of the transverse configuration is examined in comparison with its corresponding longitudinal configuration. A comparison is done with other orientation of the same KDP crystal.

Nonlinear optical characterization of single β-barium-borate nanocrystals using second-harmonic confocal microscopy

The confocal microscopy technique was applied for nonlinear optical characterization of single β-barium-borate（β-BBO） nanocrystals. The experimental setup allows measurements of the laser polarization-selective secondharmonic（SH） generation, and the results can be used to determine the nanocrystals＇ c-axis orientation, as well as to obtain information about their second-order susceptibility χ^（2）. The dependence of the SH signal on the laser polarization allowed the discrimination of individual particles from aggregates. The data were fitted using a model that takes into account the BBO properties and the experimental setup characteristics considering（i） the electrostatic approximation,（ii） the effects of the microscope objective used to focus the light on the sample in an epi-geometry configuration, and（iii） the symmetry of χ^（2） for the β-BBO nanocrystals. A signal at the third-harmonic frequency was also detected, but it was too weak to be studied in detail.

Synthesis and characterization of molecular sieve Ni-ZSM-5 and its single crystal

Using tetrapropylammonium bromide(TPABr)as a template,molecular sieve Ni-ZSM-5 and its single crystals were synthesized in a nonalkaline system in the presence of fluoride ions.By means of XRD,IR,EPMA,MAS NMR,EPR,DTA and H_2-TPR techniques,it is proved that the hetero-atom,nickel,is really located in the zeolite framework.And finally,Ni-ZSM-5 was found to have high catalytic cracking reactivity.

High Temperature Stress Rupture Anisotropy of a Ni-Based Single Crystal Superalloy

High temperature stress rupture anisotropies of a second generation Ni-base single crystal（SC） superalloy specimens with [001], [011] and [111] orientations under 900 ℃/445 MPa and 1100 ℃/100 MPa have been investigated in the present study, with attentions to the evolution of γ/γ′ microstructure observed by scanning electron microscopy and the dislocation configuration characterized by transmission electron microscopy in each oriented specimen. At 1100 ℃/100 MPa as well as 900 ℃/445 MPa, the single crystal superalloy exhibits obvious stress rupture anisotropic behavior. The [001] oriented specimen has the longest rupture lifetime at 900 ℃/445 MPa, and the [111] oriented sample shows the best rupture strength at 1100 ℃/100 MPa. While the [011] oriented specimen presents the worst rupture lifetime at each testing condition, its stress rupture property at 1100 ℃/100 MPa is clearly improved, compared with900 ℃/445 MPa. The evident stress rupture anisotropy at 900 ℃/445 MPa is mainly attributed to the distinctive movement way of dislocations in each oriented sample. Whereas, at 1100 ℃/100 MPa, together with the individual dislocation configuration, the evolution of γ/γ′ microstructure in each orientation also plays a key role in the apparent stress rupture anisotropy.