Advanced Materials Research Vol. 684

Abstract: A comparative study on off-state breakdown characteristics in nanowire JL and IM multiple gate MOSFETs has been performed for different gate bias voltages and fin widths. In order to understand the drain breakdown mechanism with different transistor structures, the device was simulated using the 3-dimensional ATLAS software. The band-to-band tunneling current and the gate-induced-drain-leakage current trigger the off-state breakdown in JL transistor and IM transistor, respectively. From experiment and simulation, the off-state breakdown voltage is lower in JL transistor than in IM transistor. As the gate is biased more negatively, the off-state breakdown voltages are increased in JL and IM transistors.

Abstract: This paper reports on the development of InP transferred-electron-device sources in mainland of China for operation at around 100 GHz. Using n+-n-n+ structure with graded doping profiles, the oscillations were obtained at 101.8 GHz from a 1 μm structure with an n-doped drift zone and the doping concentration linearly increases from 1.0×1016 to 3.0×1016cm-3. Its continuous wave radio frequency (CWRF) output power was evaluated to be several milliwatt and these results are believed to correspond to a fundamental mode operation. This result is attributed to a processing technique based on the use of etch-stop layers, removal of substrate and the formation of good ohmic contacts.

Abstract: There are various feeding methods of antenna like as coaxial probe, coupling, parasitic elements, and impedance matching. This paper adopted the microstrip line method as the feeding method of the antenna. The high frequency structure simulator is used to analyze the characteristics of the T-shaped microstrip antenna with various patch dimensions. In comparison with the basic microstrip antenna, this proposed T-shaped microstrip antenna with 40.38 % of patch dimensions has the optimum characteristics of resonant frequency, return loss, and radiation pattern at 2.0 GHz band.

Abstract: Ferroelectric thin films containing the same volume fraction of the perovskite structure (Na_0.5Bi_0.5)TiO₃ (NBT) and layered structure Bi₄Ti₃O₁₂ (BIT) were prepared with different stacking sequence. Na_0.5Bi_4.5Ti₄O₁₅ thin film, solid solution of NBT and BIT, was also synthesized to compare with the alternative layered films. Their crystal structure, microstructure and electrical properties were investigated as a function of number of interface. It was found that the interface area as well as each material property is critical to the electrical properties. The alternative layer thin films between NBT and BIT showed positive effect on the dielectric behavior than the single NBIT compound film.

Abstract: We reported the spin-on Zincsilicafilm dopant content of the diffusion process and the formation of the p+ layer were applied to fabricate GaAs solar cells and their characteristics were investigated. The p-n junction was formed by a thermal furnace from the diffusion of zinc into the GaAs substrate. It was found that the GaAs substrate must be covered by a 100-nm-thick SiO2 layer. This reduced the damage to the GaAs substrate surface morphology that occurred during high temperature treatment and made the cleaning of the residual solvate on the surface easier

Abstract: Phase locked loop (PLL) is a very common circuit in the most of the electrical devices. The systems where needed clock or data recovery or frequency synthesis, PLL is the most cost effective and efficient choice that from cellular phone in our hands to the computers, televisions, radios and a different controller, PLL is everywhere. Due to ever increasing growth of the digital systems especially in the wireless communication, the Digital PLL (DPLL) has been developed to overcome the disadvantages of analog techniques such as large noise, power hungry, parameter sensitivity etc. Besides DPLL provides faster lock-in time, better testability, stability and portability over different process. The most of the resources available discussed about the theoretical model of the DPLL which is not synthesizable, that’s why a model is presented here keeping in mind that must be fully digital and synthesizable. The proposed PLL structure is fully digital, has the design flexibility with reduced hardware, low power consumption and higher power efficiency.

Abstract: With about equal amount of austenite and ferrite in volume fraction, duplex stainless steel (DSS) is in advantage of mechanical properties and corrosive behaviors. Hence it is widely applied to the heavy castings for nuclear power plants inshore, such as impellers, pumps and valves. However, lots of cracks usually occur in these castings during manufacturing processes, because it is susceptible to precipitate the brittle intermetallic compound of sigma phase when the castings are exposed from 600 to 1000oC. In this work, the precipitation of sigma phase was observed by optical microscope (OM) and scanning electron microscope (SEM) in a cast DSS named as MAS/6001, which aged at 850oC from 5 to 300 minutes. The effect of sigma phase on the mechanical properties was analyzed by the tensile at room temperature and impact tests at -10°C. The results show that sigma phase in the MAS/6001 steel precipitated simultaneously with the secondary austenite, which obeyed the eutectoid reaction. The interfaces between austenite or secondary austenite and sigma phase were the locations where cracks generated from the void aggregation. Cracks are susceptible to propagate along or cross these interfaces, and to promote the sigma phase breaking-off, which severely deteriorated the mechanical properties.

Abstract: The behaviors of desulphidation during manual metal arc welding have been studied by means of experimental and theoretical analysis. The results indicated that the relationship curve between the distribution of sulphur in slag and deposited metal (Ls) and coating basicity of elect rode ( B1) was a parabolic shape with a maximum value. With the increase of FeO content in slag, Ls decreased and the sulphur content in deposited metal increased. With increasing coating basicity , the activity of oxygen ion in slag , FeO content in slag and oxygen potential of arc atmosphere increased. In teraction of them made that relationship between sulphur content in deposited metal and B1 had a minimum value.

Abstract: A new sheet metal forming process which can form three-dimensional surface rapidly, effectively and with lower-cost has been proposed. This paper mainly focuses on the fundamental aspects of the process. The principle of the rolling process based on bended rolls is introduced, and the methods to calculate the longitudinal bending deformation and to design the roll gap are presented. Experiments for typical surface parts are carried out. The forming results of convex surface and saddle shaped surface parts are measured and analyzed, the analyzed results demonstrated that the proposed process is a feasible and effective way of forming three-dimensional surface parts.

Abstract: There was studied the effect of directional flow of metallic melt on the forming of the structure of an ingot. Authors found out the possibility of the forming of micro- and nanostructures of solid metal by treatment in a molten state without the use of alloying elements and with negligible energy consumption on the deformation.