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An asymmetric quantum well (AQW) is designed to emit a terahertz (THz) wave by using difference frequency generation (DFG) with the structure of GaAs/Al0.2Ga0.8As/Al0.5Ga0.5As under a doubly resonant condition. It is found that the second-order nonlinear susceptibility X(2) varies with the two pump wavelengths, and it can reach the peak value of 1.61 mm/V when the wavelengths are given as λp1 = 9.756 mm and λp2 = 10.96 mm, respectively. The numerical results show that the refractive index of one pump wave in the AQW is concerned with not only its own wavelength but also the other wavelength. Phase-matching inside the AQW can be obtained through the tuning of the two pump wavelengths. [ABSTRACT FROM AUTHOR]

Porous interlayer dielectric films with interconnected pores pose a serious challenge for their integration into next-generation microchips. The opening of interconnected pores in the surface region needs to be sealed to prevent intrusion of atomic layer deposition precursors used to create metal diffusion barriers. In this paper, we report the formation of a thin, nonporous surface layer on a porous methyl-silsesquloxane-based dielectric film by NH3 plasma treatment. Depth-profiled beam positronium annihilation lifetime spectroscopy was applied to conveniently examine the formation of the dense layer. A nonporous surface layer was readily identified by the curtailment of positronium escape into vacuum through the surface. Among plasma treatments at temperatures ranging from 25 to 300°C for duration of 3-600 s, the best result was achieved at 300°C for 10 s. A very thin skin layer, ~10 nm, could be formed with little damage to the bulk of the low-k film. This thin skin layer further proved to improve the performance of Ta barriers for Cu diffusion. Chemical analysis, infrared spectroscopy, and sputtering secondary ion mass spectroscopy were also performed to examine how the plasma treatment altered the dielectric film. [ABSTRACT FROM AUTHOR]

Alkali stress can cause severe crop damage and reduce production. However, physiological processes involved in alkali stress in oat seedlings are not well understood. In this study, physiological responses and yield of oat to alkali stress were studied using the alkali-tolerant oat genotype Vao-9 and the alkali-sensitive oat genotype Baiyan 5. The results were: (i) low concentrations of alkali stress (25 and 50 mmol L−1) significantly reduced the yield and grain weight while increased the oat grain number per spike. A negative correlation between yield and malondialdehyde (MDA) content at the jointing and grain filling stages and positive correlations between yield on one hand and superoxide dismutase (SOD), and peroxidase (POD) activities on the other at the jointing stage were observed. There was a positive correlation between MDA and soluble sugar at the grain filling stage; (ii) soluble sugar content was increased at the jointing and grain filling stages and decreased at the heading stage by alkali stress; (iii) alkali stress increased the SOD activity during the heading and grain filling stages, and increased the POD activity at the heading stage. As compared to the control, the increase of MDA contents in alkali-treated oat was observed, during the jointing, heading and grain filling stages; (iv) under alkali stress, the oat genotype Vao-9 showed higher antioxidant enzyme activity and lower soluble sugar contents during the heading stage, and lower MDA contents than those in the oat genotype Baiyan 5 under alkali stress. The result suggested that the high ROS scavenging capacity and soluble sugar levels might play roles in oat response to alkali stress.