Spontaneous avalanche to plasma begins in the core of an ellipsoidal Rydberg gas of nitric oxide. Ambipolar expansion of NO$^+$ draws energy from avalanche-heated electrons. Then, cycles of long-range resonant electron transfer from Rydberg molecules to ions equalize their relative velocities. This sequence of steps gives rise to a remarkable mechanics of self-assembly, in which the kinetic energy of initially formed hot electrons and ions drives an observed separation of plasma volumes. These dynamics adiabatically sequester energy in a reservoir of mass transport, starting a process that anneals separating volumes to form an apparent glass of strongly coupled ions and electrons. Short-time electron spectroscopy provides experimental evidence for complete ionization. The long lifetime of this system, particularly its stability with respect to recombination and neutral dissociation, suggests that this transformation affords a robust state of arrested relaxation, far from thermal equilibrium. We see this most directly in the excitation spectrum of transitions to states in the initially selected Rydberg series, detected as the long-lived signal that survives a flight time of $500\ \mathrm {\mu }$s to reach an imaging detector. The initial density of electrons produced by prompt Penning ionization, which varies with the selected initial principal quantum number and density of the Rydberg gas, determines a balance between the rising density of ions and the falling density of Rydberg molecules. This Penning-regulated ion-Rydberg molecule balance appears necessary as a critical factor in achieving the long ultracold plasma lifetime to produce spectral features detected after very long delays.

In the present paper, four cDNAs encoding the alpha and gamma subunits of elongation factor 1 (EF-1) were cloned and sequenced from Nilaparvata lugens, named NlEF-1α, NlEF-1γ, and its yeast-like symbiont (YLS), named YsEF-1α and YsEF-1γ, respectively. Comparisons with sequences from other species indicated a greater conservation for EF-1α than for EF-1γ. NlEF-1α has two identical copies. The deduced amino acid sequence homology of NlEF-1α and NlEF-1γ is 96 and 64%, respectively, compared with Homalodisca vitripennis and Locusta migratoria. The deduced amino acid sequence homology of YsEF-1α and YsEF-1γ is 96 and 74%, respectively, compared with Metarhizium anisopliae and Ophiocordyceps sinensis. Reverse transcription-quantitative polymerase chain reaction (RT–qPCR) analysis revealed that the expression level of NlEF-1α and NlEF-1γ mRNA in hemolymph, ovary, fat body and salivary glands were higher than the midgut and leg tissue. YsEF-1α and YsEF-1γ was highly expressed in fat body. The expression level of NlEF-1α was higher than that of NlEF-1γ. Through RNA interference (RNAi) of the two genes, the mortality of nymph reached 92.2% at the 11th day after treatment and the ovarian development was severely hindered. The RT–qPCR analysis verified the correlation between mortality, sterility and the down-regulation of the target genes. The expression and synthesis of vitellogenin (Vg) protein in insects injected with NlEF-1α and NlEF-1γ double-stranded RNA (dsRNA) was significantly lower than control groups. Attempts to knockdown the YsEF-1 genes in the YLS was unsuccessful. However, the phenotype of N. lugens injected with YsEF-1α dsRNA was the same as that injected with NlEF-1α dsRNA, possibly due to the high similarity (up to 71.9%) in the nucleotide sequences between NlEF-1α and YsEF-1α. We demonstrated that partial silencing of NlEF-1α and NlEF-1γ genes caused lethal and sterility effect on N. lugens. NlEF-1γ shares low identity with that of other insects and therefore it could be a potential target for RNAi-based pest management.

Nanocrystalline La0.85Na0.15MnO3 ceramics were prepared via a novel method based on chemical solution combustion. Effects of sintering temperature on electrical transport and magnetic properties were systematically investigated. It was found that the resistivity increases, the magnetization decreases, and the metal-insulator transition temperature shifts toward low temperatures with the decrease of the sintering temperature. In addition, the magnetization of the samples sintered at low temperatures exhibits a broadened paramagnetic-to-ferromagnetic transition temperature. The low field magnetoresistance evidently increases with decreasing the sintering temperature due to the spin-polarized intergranular tunneling.

We present a method for solving a class of optimal control problems involving hyperbolic partial differential equations. A numerical integration method for the solution of a general linear second-order hyperbolic partial differential equation representing the type of dynamics under consideration is given. The method, based on the piecewise bilinear finite element approximation on a rectangular mesh, is explicit. The optimal control problem is thus discretized and reduced to an ordinary optimization problem. Fast automatic differentiation is applied to calculate the exact gradient of the discretized problem so that existing optimization algorithms may be applied. Various types of constraints may be imposed on the problem. A practical application arising from the process of gas absorption is solved using the proposed method.

We have studied experimentally the effect of ambient temperature on performance of the surface-passivated Al0.2Ga0.8N/GaN heterostructure field-effect transistors in the temperature range from 25°C to 250°C. The measured data have been compared with physics-based modeling of the GaN transistor characteristics under different ambient temperatures. The experimental data, showing about 33% degradation in the saturation current with a temperature increase from 25°C to 250°C, agrees well with the results of simulations performed using ISE DESSIS software. Obtained results and analytical extrapolations can be used for predicting device performance in changing environments, as well as for optimization of the device structure.

We present a theoretical model in order to describe both thermal and electronic in-plane transports in quantum dot superlattice. The model takes into account the modifications of electron and phonon transport due to the space confinement caused by the mismatch in electronic and thermal properties between dot and host materials. The developed model provides the analysis of the in-plane superlattice electronic and thermal properties versus quantum dot size and their arrangement. Numerical calculations were carried out for a structure that consists of multiple layers of Si with regimented germanium quantum dots. The simulation results of the lattice thermal conductivity are in a good agreement with experimental data.

We have investigated the preferential positioning of self-organized Ge quantum dots on Si (001) mesas fabricated in a selective epitaxial growth (SEG) mode of gas-source molecular beam epitaxy. The surface morphology was evaluated by atomic force microscopy, and for the Si SEG structures, showed mass accumulation at the periphery. Using micro-Raman spectroscopic imaging, the strain-field distribution of Si structures was studied before Ge deposition, and the results suggest a tensile strain at/near the periphery of the structure while a compressive strain at the center. These structures were subsequently used as a template for Ge dots, which tended to align along the mesa edge. The strain field distribution on Si mesas is speculated to be the driving force for preferential nucleation of Ge dots.

This paper examines factors affecting the oxidation behavior of Ir thin film electrodes and the stability of bilayer Ir/Ir-Ir-O-Si electrodes on silicon substrates. We first examine the morphology and texture of faceted IrO2 extrusions formed on the Ir films during thermal oxidation, and show that an Ir grain-growth anneal in N2 at 650°C for 5 min prior to the oxidation treatment increases both the areal density of IrO2 extrusions and the IrO2<110> x-ray diffraction intensity while decreasing apparent film roughness. We then examine the stability of bilayer lr(100 nm)/Ir(20 nm) films on polycrystalline silicon and show how fairly mild oxygen anneals of the Ir(20 nm)/Si structures can provide an in-situ formed Ir-O-Si barrier that protects the subsequently deposited Ir(100 nm) layer from silicidation reactions during annealing in N2 ambients at 750°C. Transmission electron microscopy indicates that this in-situ formed barrier at the Ir/Si interface has a two layer structure comprising an IrSix underlayer in contact with the silicon substrate and an SiO2 overlayer directly below the remaining Ir.

Metastable pseudomorphic GexSi1−x (x=8%,16%) films were deposited on p-Si(100) substrates by chemical-vapor-deposition and then implanted at room temperature with 90 keV arsenic ions to a dose of 1.5×1015/cm2. The implantation amorphizes approximately the top 125 nm of the 145 nm-thick GeSi layers. The Si-GeSi interfaces remain sharp after implantation. Implanted and non-implanted GeSi samples, together with implanted Si control samples, were subsequently annealed simultaneously by rapid thermal annealing in a nitrogen ambient at 600,700,800 × for 10,20,40s at each temperature. The implanted samples undergo layer-by-layer solid-phase epitaxial regrowth during annealing at or above 600 ×C. The amorphized and regrown GeSi layers are always fully relaxed with a very high density of dislocations (1010-1011/cm2). At a fixed annealing temperature, strain relaxation of an implanted GeSi film is substantially more extensive than that of a non-implanted one. About 50-90% of the implanted arsenic ions become electrically active after the completion of solid-phase epitaxy. The percentages of arsenic ions that are activated in the Si control samples are generally higher than those in GeSi. The room-temperature sheet electron mobility in GeSi is roughly 30% lower than that in Si for a given sheet electron concentration. We conclude that metastable GeSi on Si(100) amorphized by arsenic ions and recrystallized by solid-phase epitaxy cannot recover both its crystallinity and its pseudomorphic strain under rapid thermal annealing.

Transmission electron microscopy, conventional and high-resolution, is used to characterize the microstructural behavior of oxidized Ge0.78Si0.12 layers annealed in a reducing 95% N2+ 5% H2 ambient. An epitaxial Ge layer grows by solid-phase epitaxy on an underlying Ge0.78Si0.12 seeding layer with a Ge-Sio2 matrix positioned between them. Defect densities in the epitaxial Ge are significantly lower than in the underlying Ge0.78Si0.12. Microstructural details of this behavior are investigated.

The damage and strain produced in a nearly pseudomorphic Ge0.10Si0.90 film on Si(100) by implantation of 320 keV 28Si+ ions at 40 to 150 °C and doses from 1 to 30 x 10l4/cm2 have been measured by MeV 4He channeling spectrometry and high resolution x-ray diffractometry. Both the implantation-induced damage and strain are sensitive to the implantation temperatures. The damage as characterized by channeling decreases with the temperature of implantation for all doses and becomes minimal at 150 °C. The implantation-induced perpendicular strain does likewise, but an excess of about 6 % of its intrinsic strain remains at the strain maximum even at 150 °C.

We have studied the damage and strain produced in Ge (100) single crystals by implantation of various doses of 300 keV 28Si ions at room temperature. The analyzing tools were x-ray double-crystal diffractometry, and MeV 4He channeling spectrometry. The damage induced by implantation produces positive strain in Ge (100). The maximum perpendicular strain and maximum defect concentration rise nonlinearly with increasing dose. These quantities are linearly related with a dose-independent coefficient of ∼ 0.013 for Ge (100) single crystals implanted at room temperature. The results are compared with those available for Si (100) self-implantation. We have also monitored the strain and defects generated in pseudomorphic Ge0.1Si0.9/Si (100) films induced by room temperature 28Si ion implantation. It is found that the relationship between the strain and defect concentration induced by ion implantation is no longer a simple linear one.

Titanium aluminide was reinforced by AVCO SCS–6 continuous SiC fibers in unidirectional or 0°/+45°/–45° direction to make SiCf/Ti–A1 composites through hot-pressing of Ti and A1 powder mixture. The toughness of the composites is greatly improved at room temperature. The typical tensile elongation is over 0.8%. The room temperature strength of the composite can be sustained up to about 700°C. The processes developed in this study have two merits: (1) Ti and A1 powders instead of Ti–A1 powder can be directly used as raw materials, and (2) the mechanical properties of composites can be tailored in a similar fashion as those of conventional composites.

GaAs layers have been successfully grown on tilted (100) Si as well as porous Si substrates by molecular beam epitaxy(MBE). Rapid thermal annealing and vacuum thermal annealing have been used to further improve the quality of the epitaxial layers. We observed that the dislocation density near the interface of the heterostructure is higher for GaAs on Si substrate. Both annealing processes are proven to be useful in improving layer quality, while the vacuum thermal annealing seemed to be more effective in minimizing the residual stress.

100 μm-wide silicon-on-insulator (SOI) structures have been accomplished by utilizing silicon molecular beam epitaxial (Si-MBE) growth on porous silicon anid subsequent lateral-enhanced oxidation of porous silicon through pattern widows. A silicon beam method was used for insitu cleaning of Si surface at 750°C, and the effectiveness of this method was demonstrated by Auger electron spectroscopy and checked by the etch-pit density of the grown film. A two-step growth process of Si MBE was used to grow epitaxial layers of high quality. An electron mobility of 1300 cm2V-1s-1 was obtained by van der Pauw measurements.

Uncapped and Si3N4-capped annealing of GaAs grown with the horizontal Bridgman technique was investigated with deep-level transient spectroscopy. Electron trap concentration distributions were measured with a reduced noise DLTS system to ensure reliable data. Ion implantation using Se ions both prior to capping and through a Si3N4 cap was carried out. The evolution of defect energy levels and the changes in concentration distributions with anneal temperature were studied. It is concluded that the defects residing in the probed space-charge region can be annealed out with a Si3N4 cap at a temperature higher than 750 C.