Study of TiN/BN bilayers produced by pulsed arc plasma

Bilayers of TiN/BN were produced by using a PAPVD (Plasma Assisted Physical Vapor Deposition) pulsed vacuum arc system. The equipment is formed by a reactor composed by a vacuum chamber with two face-to-face electrodes and an RLC circuit to produce the arc discharge. To obtain the BN coating a target of h-BN was used placed on the cathode and a substrates of silicon placed on the anode. The work gas was nitrogen at a pressure of 4.4×10⁻¹ mbar and a voltage of 240 V. In order to improve the adherence of the BN film, an interlayer of TiN was grown. In this case the chamber was filled with N₂ to produce the TiN coating, with a pressure of 1.7 mbar and a voltage of 300 V. By means of XRD (X-ray diffraction), the existence of TiN was determined finding different crystalline orientation in FCC phase. An FTIR (Fourier Transform Infrared Spectroscopy) was employed to determine sp³/sp² bonding ratio in the BN film.By plotting I-V curves the electrical properties of the bilayer were studied, observing a semiconductor behavior and this result was compared to the silicon substrate without coating.     

半导体器件动力模型的有限元法仿真与分析

该文采用有限元方法对动力模型进行了数值仿真。首先推导出模型方程，然后根据将要采用的数值方法提出了新的变量替换关系和无量纲化参数，再讨论了一般器件的边界条件，最后对具有亚微米级的GaAs MESFET进行了数值仿真，数值结果表明在一定的条件下，电子的流动具有跨音速特征。     

High aspect ratio CdS nanowires synthesized in microemulsion system

CdS nanowires with typical length more than 8 μm and width of 30 nm on average have been successfully synthesized through Cd(NO₃)₂ reacting with CS₂ and ethylenediamine in microemulsion system of sodium dodecylbenzene sulfonate (SBDS). The microstructures of the as-synthesized CdS nanowires were characterized using XRD, transmission electron microscopy (TEM) and HRTEM. The possible formation mechanism was discussed. The morphologies of CdS sample strongly depend on the concentration of surfactant in solutions.     

Ionic liquid assisted sonochemical synthesis of NiS submicron particles

A novel synthesis methodology is reported for the preparation of NiS submicron particles in a green solvent 1-butyl-3methylimidazolium tetrafluoroborate (BMImBF₄) ionic liquid (IL), using ultrasonic sonochemical technique. Structural, morphological and optical properties of nickel sulfide powders were obtained by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and diffuse reflectance spectroscopy (DRS). Composition was corroborated by energy dispersive X-ray spectroscopy (EDXS), both in the SEM and in the TEM. Regular shape particles were obtained under high-intensity ultrasonic irradiation for 105 min from the reaction between nickel nitrate and thioacetamide in ethanol/BMImBF₄ (80:20), respectively. After vacuum annealing treatment at 180 °C overnight, spherical crystalline NiS particles were observed. The powders showed a band gap of 0.74 eV.     

Semiconductor supply planning by considering transit options to take advantage of pre-productions and order cancellations

One of the objectives of supply planning is to find when and how many productions have to be started to minimize total cost. We aim to find the optimum. Base data like the length of transit time are important parameters to plan for the optimum start of production. In this research, we considered two kinds of transit options: normal transit and emergency transit, and we distinguished between planned and executed transit. The decision regarding which transit option to choose for the execution is trivial because emergency is only used when it is needed since normal transit is more cost efficient. However, for planning purpose, it is more difficult to decide which transit option should be used since the uncertainty in demand and supply between plan and execution can allow to plan an emergency transit but to execute the delivery with normal transit, which is a huge benefit in the competitive capital intensive semiconductor industry. If we planned an emergency, we can save inventory and production cost as we can delay the start of production. In contrast, we need pay additional transit cost in case that emergency transit is actually executed. Many characteristics of the semiconductor industry, which might be the front runner for many other industries, are considered in this model such as demand uncertainty, supply uncertainty and economic volatility. In our numerical experiments, we could gain the optimum, depending on each economic situation. Furthermore, we conducted sensitivity analysis of the effect of demand and supply uncertainties on total cost.     

Photoluminescence and X-ray luminescence of Pb0.30Cd0.70I2 solid solutions. Comparative study

The nature and relative contributions (RCs) of various radiative recombination processes to the photoluminescence (PL) spectra for bulk nanostructured Pb_0.30Cd_0.70I₂ solid solutions have been established at different temperatures. The analysis indicates that the PL is caused by free, bound and self-trapped excitons as well as by donor-acceptor pairs emission with the participation of shallow and deep acceptor centers. It was shown that X-ray luminescence (XRL) spectra are also determined by these recombination processes. However, their RC and the temperature evolution are considerably different. Besides, XRL spectra contain an intense long-wavelength band associated with the emission of many LO-phonons. It was shown that the deep luminescence surface states, associated with the self-trapped excitons and deep intrinsic defects, mainly determine the intensity of XRL spectra both at 80 K and room temperature. The results obtained open the way to the optimization of the scintillator properties of the investigated materials.     

Tunable permittivity in polymer composites filled with Si-based semiconductors by regulating induced polarization

Induced polarization shows a significant influence on dielectric permittivity of 0–3 polymer composites containing Si-based semi-conductive fillers. The nature of induced polarization is the increased electric conductivity or decreased band gap in Si-based semi-conductive fillers. In this work, the dependence of induced polarization onto particle size of α-SiC filler together with polarity of polymer matrix and Si-based semi-conductive filler has been elaborately investigated by detecting the permittivity of composites. It was found that increasing the grain size of SiC filler, improving the polarity of polymer matrix and reducing the band-gap of Si-based semi-conductive filler could favor the enhancement of the overall induced polarity in the composites. As a result, the significantly improved dielectric permittivity of composites higher than both of the neat polymer and filler was observed depending on the constituents of the composites. The highest dielectric permittivity of ~215@1 kHz was achieved in poly(vinyl alcohol) based composite filled with 60 vol% of 12 µm SiC particles. The dielectric permittivity of these 0–3 composites could be well tuned in a wide range through altering their constituents. This work might open a facile route to obtain the promising high-performance dielectric composite materials by regulating the degree of induced polarization.     

Coupled nanowire-based hybrid plasmonic nanocavities on thin substrates

We theoretically analyze nanowire-based hybrid plasmonic nanocavities on thin substrates at visible wavelengths. In the presence of thin suspended substrates, the hybrid plasmonic modes, formed by the coupling between a metal nanowire and a dielectric nanowire with optical gain, exhibit negligible substrate-mediated characteristics and overlap better with the gain region. Consequently, the confinement factor of the guided hybrid modes is enhanced by more than 42%. However, the presence of significant mirror loss remains the main challenge to lasing. By adding silver coatings with a sufficient thickness range on the two end facets, we show that the reflectivity is substantially enhanced to above 50%. For a coating thickness of 50 nm and cavity length of about 4 μm, the quality factor is above 100.     

立磨液压系统的自动化控制技术的研究

数字技术的数学基础——离散数学、逻辑数学等，早在17、18世纪就已经出现。但是发展成为数字技术并付诸实用，随着半导体器件、集成器件和超大规模集成器件的出现，数字技术在液压系统中的应用迅速而又普遍地发展起来。     

Promising methane gas sensor synthesized by microwave-assisted Co3O4 nanoparticles

The morphology and gas sensing characteristics of Co₃O₄ nanoparticles prepared using the microwave irradiation were investigated. XRD and TEM are used to analyze the structural and the morphological properties of the prepared nanoparticles. XRD results confirmed the formation of pure phase of these nanoparticles. The gas sensor based on the synthesis Co₃O₄ nanoparticles reveals faster response and recovery time at low temperature detection toward methane gas. Specifically, for methane concentration of 1%, the response and the recovery times at 200 °C are 100 s and 50 s, respectively. Furthermore, the sensing characteristics of Co₃O₄ nanoparticles were improved by increasing the operating temperatures and gas concentrations as well. The experimental results clearly demonstrate the potential use of Co₃O₄ nanoparticles as a sensing material in the fabrication of CH₄ sensors.