On the mechanism of the external magnetic field action on the electron temperature and ion charge state distribution in a vacuum arc plasma

When an external axial magnetic field is applied to a vacuum arc, the radial expansion of plasma from cathode spots transforms into a plasma flow along the magnetic field, provided that the electron-ion collision frequency is smaller than the Larmor frequency. As the magnetic field strength increases, the diameter of the resulting cylindrical channel decreases. This leads to an increase in the electron temperature and the ion charge due to enhanced Joule heating of the plasma. Unlike the intrinsic azimuthal magnetic field, the external axial field only restricts expansion of the plasma, rather than compressing the plasma jet.     

Ion deposition in a crossed E×B field system with vacuum arc plasma sources

The system with crossed magnetic and electric fields and vacuum arc plasma sources for ion deposition and low-voltage plasma treatment and plasma immersion ion implantation has been investigated. The use of crossed E×B fields provides intense gas ionization and suppresses sheath expansion. Maximum deposition rate of about 1 μm min⁻¹ was obtained on the target surface located under the area where intense ionization of reactive gas occurs (circular area of about 40 mm wide around the target). Without magnetic field the maximum rate of only 0.15 μm min⁻¹ can be achieved. In the crossed E×B fields, high-quality dense TiN coating was obtained. High ion current density to the target surface reaches 500 A m⁻², provides effective cleaning of the target surface and heating of the growing film. The ratio of metal plasma current and reactive gas ion current reaches 2.1 and can be easily changed by adjusting the magnetic field strength, without changing the vacuum arc gun current. The uniform film deposition around circumference of the target is provided as a result of ion magnetization in the crossed field zone. The uniform film deposition along the entire target length can be provided by moving magnetic field up and down.     

Ion energy distribution of an inductively coupled radiofrequency discharge in argon and oxygen

We report an experimental investigation of the ion energy distribution in an inductively coupled electron cyclotron wave resonance (ECWR) discharge with a superimposed static magnetic field. The inductively coupled discharge is sustained by applying a 13.56 MHz radiofrequency (RF) power to an aluminium single-turn coil located inside the vacuum chamber. The source region was separated by a grid from the diffusion region. Ion energy distribution (IEDF) measurements employing an energy-dispersive mass spectrometer or plasma process monitor (PPM) whose entrance opening was 15 cm away from the grid were performed in the diffusion region. The IEDF is composed of two peaks; a low-energy peak due thermalized ions and a high-energy peak due to ions coming directly from the source region without undergoing thermalization. The energetic difference between the groups thus reflects the plasma potential difference between the source region and the diffusion region. The pronounced intensity variation of the high-energy peak with increasing pressure is caused by charge-changing collisions yielding a depletion of the high-energy ions with increasing effective path length.     

Estimate of the negative ion density in reactive gas plasmas

The negative ion density in a SF₆/Ar double plasma is estimated. Here, the density ratio of negative ions to positive ions is evaluated from the reduction rates of the ion and electron saturation current. Furthermore, the negative ion density obtained with this method is confirmed to agree with that calculated from the measured phase velocity of the ion acoustic wave (fast mode) when <0.6, where the positive and negative ion mass are obtained from the spectrum analysis with a quadruple mass spectrometer (QMS) system. The negative ion density in fluorocarbon ECR plasma is also estimated by means of the Langmuir probe method. It is found that in fluorocarbon ECR plasma is less than 0.5.     

Determining the number of layers in graphene films synthesized by filtered cathodic vacuum arc technique

We have synthesized graphene film by the filtered cathodic vacuum arc (FCVA) technique and determined the number of layers in graphene films by various techniques. Amorphous carbon (a-C) films of different thicknesses (1, 2, 3, 6, 10 and 18 nm) were synthesized by the FCVA technique on Si/SiO₂/Ni substrate and then annealed in vacuum at 800°C and cooled down to room temperature naturally to obtain graphene. Prepared graphene films were transferred on different substrates and characterized by the Raman spectroscopy, UV-VIS-NIR spectroscopy, high-resolution transmission electron microscopy (HRTEM), optical microscopy, atomic force microscopy (AFM) and sheet resistance to determine the number of layers present in the graphene films. Raman spectra of the prepared graphene films exhibit that there is red shift in the position of D, G and 2 D peak. The value of I_2D/I_G varied from 0.18 to 0.51, I_D/I_G varied from 0.82 to 1.02 and full width at half maximum of 2 D peak varied from 101.2 to 128.0 cm^?1, for different thicknesses of graphene films, respectively. The value of transmittance decreases from 97 to 63.7% and that of sheet resistance increases from 460 to 1400 Ω/square with the increase in the thickness of the prepared graphene film. The HRTEM and AFM study revealed that the graphene synthesis from 1 nm thick a-C film possesses a single layer structure.     

A simulated annealing algorithm to the multi-period fixed charge distribution problem associated with backorder and inventory

This paper addresses a multi-period fixed charge distribution problem associated with backorder and inventory. The objective is to determine the size of the shipments, backorder and inventory at each period, so that the total cost incurred during the entire period towards transportation, backorder and inventory is minimised. A pure integer non-linear programming problem is formulated. A simulated annealing based heuristic is proposed to solve and is illustrated. The proposed methodology is evaluated by comparing its solutions with the lower bound and equivalent variable cost solutions. The comparisons reveal that the simulated annealing generates better solutions than the equivalent variable cost solutions and is capable of providing solutions closer to the lower bound solutions of the problems.     

一种用于制冷系统稳定运行时制冷剂分布测试的新方法

介绍制冷系统动态和稳态过程的理论和实验研究现状,总结现有实验研究中的测试方法,并分析各自的优缺点。提出一种相对高效省时的制冷剂回收测试方法,同时介绍这种方法的测试原理、实验步骤,并根据实际测试结果,分析误差产生的原因及避免方法。     

Nonuniform metallic state in manganites and cuprates

Local lattice distortions suggesting nonuniform charge distributions were found to be a common feature of manganites and cuprates in the metallic state by neutron scattering studies. The atomic pair-density function (PDF) determined by pulsed neutron powder diffraction showed that in La_1-xSr_xMnO₃ doped holes form lattice polarons which persist even in the metallic state. In La_1.85Sr_0.15CuO₄ the energy width of the LO phonons around (π,0) determined by inelastic neutron scattering reflects magnetic satellites indicative of spin charge stripe formation. The implications of such nonuniform charge distribution for metal-insulator transition and superconductivity are discussed.     

Structures and light emission properties of nanocrystalline FeSi2/Si formed by ion beam synthesis with a metal vapor vacuum arc ion source

Thin layers of nanocrystalline FeSi₂ embedded in Si structures have been formed by Fe implantation using a metal vapor vacuum arc (MEVVA) ion source under various implantation and thermal annealing conditions. The microstructures were studied in details and correlated with the photoluminescence (PL) properties. It is found that higher lattice coherence between the FeSi₂ nanocrystals and the Si matrix is associated with better light emission efficiency. Multiple-cycle implantation schemes were introduced and it is shown that with appropriate process design the dose quenching effect can be suppressed to achieve light emission enhancement in higher dose samples. De-convolution of the PL spectra into two or three peaks was performed and their temperature and excitation power dependence were analyzed. The analysis results indicate that the 1.55-μm emission really originated from FeSi₂ and that the emission peaks are likely donor- or accepted-level-related. MOS structures with the incorporation of implanted nanocrystalline FeSi₂ were fabricated. Electroluminescence (EL) spectra from these devices showed two peak features of which one peak corresponds to FeSi₂ emission and the other corresponds to enhanced Si band-edge emission. Clear room-temperature EL signals from these device structures were observed. A model is proposed to qualitatively understand the temperature dependence of the EL spectra.     

The study on the light intensity distribution of interference by the topological charge of singular vortex beam

This study theoretically analyzed the angular momentum general formulas and equations of singular vortex beam and studied light intensity distribution characteristics of the singular vortex beam with mixing interference of a the singular vortex beam by numerical simulation methods. In order to reveal the light intensity distribution, the author chose three cases to perform experiments and collect data: two identical singular vortex beams, two singular vortex beams with equal and opposite topological charges, and two singular vortex beams with unequal topological charges.     

ICP-MS离子提取模型的建立与传输透镜的参数优化

电感耦合等离子体质谱(ICP-MS)具有对一种或多种基本元素、同位素快速分析的能力,在诸多领域有其广泛应用。本文对ICP-MS接口部分中等离子体气流及离子的运动过程进行了理论分析,基于Child鞘层定律首次建立了正离子提取模型,以确定离子束形成的初始位置。然后在忽略空间电荷效应的前提下,利用电、离子光学模拟软件SIMION计算离子在透镜传输系统中的运动轨迹,通过调整透镜电极电压参数来获取最佳的离子传输效率,并以此作为分析实验前透镜调谐工作的理论依据。     

沉积气压对电弧离子镀制备MgO薄膜的结构及性能的影响

采用阴极真空电弧离子沉积技术在玻璃及Si衬底上成功地制备了具有择优结晶取向的透明MgO薄膜。利用X射线衍射仪（XRD）、扫描电子显微镜（SEM）及紫外-可见吸收光谱仪分别对MgO薄膜微观结构、表面形貌及可见光透过率进行了测试与分析。XRD结果表明,所制备的MgO薄膜具有NaCl型立方结构的（100）、（110）和（111）3种结晶取向,在沉积气压为0.7～3.0Pa的范围内,薄膜的择优结晶取向随沉积气压的升高先由（100）转变为（110）,最后变为（111）。SEM图表明随着沉积气压的升高,MgO薄膜的晶粒逐渐变小,薄膜结晶质量变差。在380～900nm范围内,沉积气压为0.7Pa下制备的MgO薄膜其可见光透过率高于90%,随着沉积气压的升高,薄膜的可见光透过率有所下降。     

工艺参数对阴极电弧离子镀ZrN薄膜表面形貌及结构的影响

本文采用阴极电弧离子镀技术制备了ZrN膜层,研究了工作气压、偏压、弧流等工艺参数对ZrN膜层表面形貌和结构的影响,分别用扫描电镜(SEM)、X射线衍射仪(XRD)分析了膜层的表面形貌及相结构。结果表明:工作气压、偏压、弧电流等工艺参数对ZrN膜层的表面形貌有较大的影响,在本实验内适当提高N2压强、偏压以及在稳弧前提下降低弧流有利于减少大颗粒,改善ZrN膜层表面形貌,提高膜层综合性能;不同工艺参数下制备的ZrN膜层均具有典型的面心立方结构,工作气压和弧电流对ZrN膜层晶体生长方向的影响较小,偏压对晶体生长方向的影响显著,在20 V偏压下,晶体呈(200)面择优取向,继续提高偏压(100 V~300 V),晶体生长呈(111)面择优取向。     

The influence of deposition rate on the stress and microstructure of AlN films deposited from a filtered cathodic vacuum arc

Aluminium nitride (AlN) thin films have been reactively deposited using a filtered cathodic vacuum arc system. A pulsed substrate bias was applied in order to increase the average energy of the depositing species. The stress and microstructure of the films were determined as a function of the deposition rate and pulse bias amplitude/frequency. The stress generated in films grown with high voltage pulsed bias depended on the deposition rate and a transition from tensile stress to compressive stress occurred as the deposition rate increased. This trend was accompanied by progressive changes in the microstructure. In order of increasing deposition rate, the films exhibited: a porous structure with tensile stress; a dense AlN film with compressive stress; and a dense AlN film showing evidence of a thermally induced reduction in stress.     

Decoherence of the two-mode squeezed vacuum state in a diffusion process

We have studied the case in which one mode of the light field in the two-mode squeezed vacuum state evolves in a diffusion channel. By virtue of thermo-entangled state representation and the technique of integration within an ordered product, the evolution formula of the field density operator is given. Its non-classical properties, such as squeezing effect, antibunching effect, the violation of Cauchy–Schwartze inequality and the entanglement property between two modes, are studied. The influences of the squeezing parameter and the dissipation time on the non-classical properties are discussed. The results obtained by the numerical method show that its non-classical properties are all weakened with the dissipation. On the other hand, its squeezing effect and the entanglement property between two modes are strengthened, but its antibunching effect and the violation of Cauchy–Schwartze inequality are weakened with the increase of the squeezing parameter.     

Structural and optical properties of Ti-doped ZnO thin films prepared by the cathodic vacuum arc technique with different annealing processes

Highly transparent Ti-doped ZnO thin films were prepared on glass substrates at a deposition rate of approximately 33 nm/min using the cathodic vacuum arc technique with a Zn target power of 550 W and a Ti target power of 750 W, respectively. X-ray diffraction measurements have shown that the Ti-doped ZnO thin film with a vacuum post-annealing condition is c-axis oriented but an amorphous phase at the other post-annealing atmosphere and as-deposited condition. Transmittance measurements show that the best optical quality of the Ti-doped ZnO thin films occurred at a post-annealing atmosphere of N₂/H₂ mixed gases. Additionally, the optical transmittance of all films has been found more than 85% in a range of 500-700 nm. The lowest electrical resistivity was 3.48 × 10⁻³ Ω cm, obtained on as-deposited films. However, the post-annealing condition greatly increased the resistivity.     

The current column contraction and ion charge increase induced by the current build-up in a pulsed vacuum discharge

It is shown that three current build-up regimes may be realized in a pulsed vacuum discharge, depending on the relationship between the pulse duration τ and the characteristic times of the plasma flow (τ_L) and the cathode spot spreading (τ_S). For a rapid build-up (τ<τ_L), the cathode plasma jet exhibits the neck formation with high values of the plasma temperature and density. At a slow current increase (τ_L<τ<τ_S), the current column is subject to a uniform magnetic contraction, while at a very slow current growth rate (τ>τ_S), the contraction becomes insignificant. The first two cases give rise to additional nonequilibrium ionization in the current column, which leads to the ion charge increasing with the current. The third case is characterized by a “frozen” ion composition corresponding to the plasma parameters in the near-cathode region.     

Electronic charge transfer in cobalt doped fullerene thin films and effect of energetic ion impacts by x-ray absorption spectroscopy

We report on the electronic charge transfer in cobalt doped fullerene thin films by means of near-edge x-ray-absorption fine structure (NEXAFS) spectroscopy measurement. Co-doped fullerene films were prepared by co-deposition technique and subjected to energetic ion irradiation (120 MeV Au) for possibly alignment or interconnect of randomly distributed metal particles. Polarization dependent NEXAFS spectra revealed the alignment of Co and C atoms along the irradiated ionic path. The structural changes in Co-doped as-deposited and ion irradiated fullerene films were investigated by means of Raman spectroscopy measurements. Downshift of pentagonal pinch mode A_g(2) in Raman spectroscopy indicated the electronic charge transfer from Co atom to fullerene molecules, which is further confirmed by NEXAFS at C K-edge for Co-doped fullerene films.