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In the present study, CVD-SiC samples were implanted with 50 keV Mg ions and co-implanted with 30 keV He ions and 50 keV Mg ions at room temperature, and then annealed at 1573 K for 20 h. The recrystallization and Mg diffusion behavior after annealing were characterized and analyzed. ToF-SIMS profiles indicated that Mg diffused faster in the Mg only implanted sample than in the He and Mg co-implanted sample. TEM results showed that He atoms diffused toward the surface regions with high damage to form He bubbles, which aided the recrystallization of the amorphous layer. Calculations by Mean Square Displacement (MSD) method based on MD simulation prove that the diffusion coefficient of Mg in the amorphous SiC is much higher than that in the crystal SiC. These results indicated that the accelerated recrystallization by He bubbles and themselves were responsible for inhibiting the diffusion of Mg in SiC.

Semi-Insulating Gallium Arsenide (SI-GaAs) was implanted with 1.5 MeV He+ ions and THz photoconductive antenna (PCA) was prepared on the implanted SI-GaAs surface. The antenna was applied as the THz wave emission source of a terahertz time domain spectroscopy (THz-TDS) and the THz wave emission ability was studied as a function of the implantation dose. It is found that the THz signal intensity increases with increase of implantation dose, and after reaching to a peak value the THz signal intensity decreases with further implantation. The best THz emission ability was achieved at a dose value between 1 x 10(15) and 1 x 10(16) ions/cm(2). It is believed that the implantation induced defects in the 1 mu m-thick surface area are responsible for the enhanced THz emission ability. The work proved that better THz photoconductive antenna than that made by low-temperature-grown GaAs (LT-GaAs) can be produced through He-ion implantation at proper dose. (C) 2013 Elsevier B.V. All rights reserved.

One dimensional C-C nanostructure, diamond-graphite nanorods, was synthesized by the argon rich microwave plasma chemical vapor deposition method. The nanostructures were characterized by scanning electron microscopy and transmission electron microscopy techniques. The diamond nanorods (DNRs) consist of single-crystalline diamond cores of 2-5 nm in diameter and several tens of nanometer in length. The DNRs are encapsulated in a graphitic shell of variable thickness. Raman and X-ray diffraction spectra also indicated the coexistence of diamond and graphite phases in the film. The addition of nitrogen is considered to be helpful for the highly efficient formation of graphite shell. The high content of methane in the gas mixture in the presence of argon rich environment is suggested to be responsible for the one dimensional growth. (C) 2009 Elsevier B.V. All rights reserved.

Si1−xGex thin films on the Ar+ ion-implanted Si substrates with different implantation energy (30 keV, 40 keV and 60 keV) at the same implantation fluence (3 × 1015 cm−2) were grown by ultra high vacuum chemical vapor deposition (UHVCVD). Various characterization technologies were used to characterize these Si1−xGex films. Investigations by Rutherford backscattering spectroscopy/channeling (RBS/C) demonstrate that thin Si0.81Ge0.19 films could be epitaxially grown on the ion-implanted Si substrates, although there existed obvious crystal defects. These relaxation extents of Si0.81Ge0.19 films on the Ar+ implanted Si substrates are larger than that in the un-implanted case, which were determined by Raman spectra. Atomic force microscopy was used to determine the surface morphology of Si0.81Ge0.19 films. The microstructures of these SiGe/Si hetero-epitaxial materials were investigated by transmission electron microscopy (TEM). All the experimental results demonstrated that a highly relaxed (relaxation extent of 82.3%) Si0.81Ge0.19 thin film (50 nm) growing on the 30 keV Ar+ ion-implanted Si substrate is optimal, which is compared to those SiGe films grown on the ion-implanted Si substrate under other implantation condition.

Fe x N (1.6 is produced by RF-sputtering of pure iron under high purity argon and nitrogen atmosphere. Abundances of Fe, N, O and C are analyzed by proton deep elastic scattering, while X-ray photoelectron spectroscopy (XPS) is used to detect the oxidation of iron. Mossbauer spectroscopy was used to characterize the samples as-sputtered and after annealing at 200°C, 250°C and 300°C for 30 minutes, respectively. X-ray diffraction and Mossbauer results show that for the chemical ratio of iron in FexN approaching 2, orthorhombic ζ-Fe2N will transform into hcp e-FexN or quasi-ZnS type structure with an increase of nitrogen content in the sputtering atmosphere or after annealing. The first neighbor shell of iron is either rich or depleted of nitrogen in e-Fe2N.

IT governance is a very effective way to keep the goal of e-government development consistent with that of public services. The paper, based on the IT governance theory, analyzes the key problems in China's e-government development, and proposes a governance framework for e-government from perspectives including value chain management, decision-making power and responsibility model, and performance evaluation model. Keywords-E-government; IT Governance; performance evaluation To build a service-oriented government for the purpose of effective implementation of e-government services has become a primary concern in the field of public administration. However, our research finds that government organizations at all levels, though assumingly take transparency and interactivity as their ultimate goal in their construction projects, have found it difficult to reflect their goal into the actual management practices as a result of the lack of effective coordination mechanisms, and deviation from their original goal often occurs during actual construction. In this regard, this paper summarizes the current key problems in this field, then introduces IT governance as a theoretic approach, and finally, proposes a service-oriented government framework for reference.

Dark current mechanisms of terahertz quantum-well photodetectors (THz QWPs) are systematically investigated experimentally and theoretically by measuring two newly designed structures combined with samples reported previously. In contrast to previous investigations, scattering-assisted tunneling dark current is found to cause significant contributions to total dark current. A criterion is also proposed to determine the major dark current mechanism at different peak response frequencies. We further determine background limited performance (BLIP) temperatures, which decrease both experimentally and theoretically as the electric field increases. This work gives good description of dark current mechanism for QWPs in the THz region and is extended to determine the transition fields and BLIP temperatures with response peaks from 3 to 12 THz.

The influences of the process gases, such as methane and nitrogen concentration on the morphology of nanocrystallites diamond films are assessed. It has been found that the concentration of CH4 in the reactant gases is important to control the morphology of diamond nanocrystallites. The morphology of nanocrystallites changes from granular to rodlike shape by changing methane concentration in Ar/H2/CH4 microwave plasma. The addition of nitrogen is considered to be helpful in the formation of graphite content and for increasing the deposition rate. No considerable changes in the morphology of diamond nanocrystallites were observed by varying nitrogen concentration in the feed gases as observed by scanning electron microscopy. Although Raman spectroscopy indicated that the amount of sp2-bonded carbon increased by the addition of nitrogen in the plasma. The high concentration of methane in the gas mixture due to the presence of argon rich environment is suggested to be responsible for the formation of diamond...