探讨电弧离子镀中“大颗粒”净化方法

传统电弧离子镀存在着大颗粒污染、沉积温度相对较高和易引发微弧击穿效应等诸多不足,制约其在精细薄膜、低温沉积和功能薄膜等方面的应用。本文简要介绍了电弧离子镀中大颗粒的形成机理,旨在探讨用磁场控制、脉冲电弧、磁过滤及脉冲偏压等方法来减少大微粒污染及其作用机理。     

电弧离子镀的旋转横向磁场弧源设计

电弧离子镀工艺中电弧蒸发产生的大颗粒污染严重影响了所沉积涂层的性能.为了从源头上解决大颗粒难题,本文提出了一种新的旋转横向磁场的设计思路,通过频率和强度可调且覆盖整个靶面的旋转横向磁场控制弧斑的运动.通过有限元模拟磁场的分布,对旋转横向磁场控制的电弧离子镀弧源进行了优化设计.并根据方案制作了旋转磁场发生装置及其电源,使该弧源的旋转磁场具有多模式可调频调幅的功能,用以改善弧斑的放电形式,提高靶材刻蚀均匀性和靶材利用率,减少靶材大颗粒的发射,用以制备高质量的薄膜以及功能薄膜,以拓展电弧离子镀的应用范围.     

新型双弯曲磁过滤阴极真空电弧沉积系统的磁场模拟计算

本文用ANSYS软件对新型的45°双弯曲磁过滤阴极真空电弧沉积系统中的磁场分布进行了模拟计算,并结合等离子体传输和电弧源弧斑运行稳定性进行了分析。在建立的数学模型基础上,分别研究了磁过滤弯管磁场空间分布对拟定的不同出射方向上的111个碳离子束的传输行为影响,和外加永久磁体对电弧源附近磁场空间分布的影响。结果表明,在优化的磁过滤弯管磁场空间分布情况下,111个碳离子束流可全部通过磁过滤弯管,并高效传输到基材表面。当电弧靶源后部的外加永久磁体磁化方向与弯管上的磁化方向相反,且磁矫顽力大于600 kA/m时,阴极靶弧源附近的磁力线空间分布更利于控制阴极弧斑长时间运行稳定性,这对延长弧斑寿命、提高等离子体的沉积效率、提高靶材表面刻蚀均匀性和获得高性能的ta-C薄膜生长具有重要理论意义。     

过滤式真空电弧离子镀膜技术及应用

介绍了一种新的镀膜技术—过滤式真空电弧离子镀膜技术。针对典型的过滤式真空电弧镀膜装置，描述了其结构组成，分析了它的工作原理。分析结果表明，该技术与传统真空电弧离子镀膜技术相比，可有效地消除宏观颗粒对镀层的污染，可广泛应用于制作各种微电子膜透明导电薄膜（ＩＴＯ）以及类金刚石（ＤＬＣ）薄膜。     

电弧离子镀弧源的研制进展

电弧离子镀作为一种经典的PVD技术已经在涂层领域得到了长足的发展,但沉积过程中产生的宏观大颗粒问题限制了其在纳米功能涂层中的应用.弧源作为电弧离子镀膜设备的核心部件,是宏观大颗粒产生的源头,直接决定镀膜系统的成膜质量.阐述了三类不同靶材形式传统弧源的特点,分析总结了近年来新型弧源研究和应用现状,综述了新型弧源在控弧磁场...     

脉冲叠加直流偏压电弧离子镀TiCrNx薄膜的制备与性能研究

采用脉冲叠加直流偏压电弧离子镀技术在硬质合金刀具表面制备TiCrNx薄膜,利用XRD,SEM,多功能材料表面性能测试仪等对TiCrNx薄膜进行表征.结果表明,TiCrNx与TiN薄膜相比,硬度有所下降.膜-基结合力与靶材阴极弧电流及偏压有关.     

工艺参数对电弧离子镀沉积铜薄膜微结构及性能的影响

采用脉冲偏压电弧离子镀技术在不同工艺参数(弧电流、基体负偏压)水平下制备了一系列铜薄膜。利用金相显微镜、腐蚀失重试验和双向弯曲试验分别研究了弧电流和基体负偏压对铜薄膜组织结构、耐腐蚀性能和结合性能的影响。结果表明,弧电流由40A增加到80A,薄膜表面颗粒含量明显增加,大颗粒尺寸由13.71μm增加到19.36μm,膜层平均腐蚀速率降低;随着弧电流提高,薄膜结合性能先降低后提高,60A时膜层结合性能最理想;随着基体脉冲负偏压升高,薄膜结合性能提高,薄膜表面颗粒含量及其尺寸减小、负偏压达到200V时大颗粒净化效果明显;基体脉冲负偏压由20V升高到180V,膜层平均腐蚀速率先降低后升高,140V时膜层耐腐蚀性能最佳。     

离子镀中弯管磁过滤器的效率和颗粒去除效果的研究

真空多弧离子镀沉积四面体非晶碳薄膜(ta-C)过程中,利用90°磁过滤器弯管去除大颗粒。本文探究了磁场强度、弯管偏压、弧电流和挡板孔径对弯管中离子传输效率(离子流)的影响,同时研究了薄膜表面颗粒去除情况。实验结果表明,弯管中离子流随磁场强度增强而增大,但增大磁场强度会导致颗粒数量增多;在中低磁场强度下,弯管偏压约为+15 V时可获得较高的离子传输效率,相比于不施加偏压提高了近70%;减小挡板孔径可使沉积速率降低,但可以显著改善大颗粒过滤效果;改变弧电流对弧源离子产生率和过滤器传输效率几乎没有影响,减小弧电流能够降低大颗粒的发射数量。本文研究内容为工业应用中采用磁过滤弯管减少薄膜大颗粒提供参考。     

多模式交变耦合磁场辅助电弧离子镀弧源设计

采用有限元模拟对多模式交变耦合磁场进行了优化设计,介绍了多波形电磁线圈控制电源的原理,并对按此原理制作的电源进行了测试,分析讨论了不同波形励磁电流条件下磁场对于弧斑运动的影响,提出了一种多模式交变耦合磁场辅助电弧离子镀弧源设计原理及方案。研究表明:轴对称发散磁场有推动弧斑向外扩展的趋势,轴对称拱形磁场将弧斑约束在固定的轨道,反极性聚焦导引磁场有约束弧斑在靶材中心的趋势,多模式反极性动态聚焦导引磁场与轴对称发散磁场或者拱形磁场叠加,可形成动态的拱形耦合磁场,动态的控制弧斑运动,改善弧斑放电状态,减少颗粒发射;在聚焦磁场引导下,等离子体稳定的传输,同时可以增强等离子体的粒子碰撞机率,提高离化率和离子密度。反极性动态聚焦导引磁场线圈由多波形电磁线圈控制电源驱动,可输出频率、幅值单独可调的直流及直流偏置的三角波、矩形波、馒头波、正弦波及其他形式的交变电流,实现对弧斑的多种模式控制。     

类金刚石薄膜在不锈钢表面结合强度及耐腐蚀性研究

类金刚石(DLC)薄膜与不锈钢的结合强度是DLC薄膜应用于血管支架表面改性的关键技术问题.利用磁过滤阴极真空弧源沉积方法在316L不锈钢表面沉积DLC薄膜,研究沉积时基体偏压、薄膜厚度以及钛过渡层对DLC薄膜与基体结合强度的影响.研究结果表明,316L表面制备相同厚度的DLC薄膜,采用-1000V脉冲偏压制备的薄膜结合强度明显优于-80V直流偏压下制备的DLC薄膜;随着DLC薄膜厚度的增大,DLC薄膜与316L基体的结合力下降;316L不锈钢表面制备一层100nm的钛过渡层之后可以改善DLC薄膜的结合状况,并且经过20%的拉伸变形后,DLC薄膜完整,耐蚀性优于未表面处理的316L不锈钢.以上研究结果表明,磁过滤阴极真空弧源方法制备DLC薄膜与316L结合强度高,可以有效的提高316L的耐腐蚀性,是一种具有应用前景的血管支架表面改性方法.     

The effect of axial magnetic filed on the process of anode spot formation in a vacuum-arc discharge with CuCr50 electrodes

An experimental study is made of the effect of an external axial magnetic field on the process of anode spot formation in a pulsed vacuum-arc discharge in the range of currents from 5 to 12 kA in a discharge gap with CuCr50 electrodes. The times and currents, at which an anode spot is formed, are determined for each amplitude value of current depending on the magnitude of magnetic field. The minimal value of magnetic field preventing the anode spot formation is determined for each current. The measured values of diameters of the current channel are used to calculate the anode temperature. It is demonstrated that, under experimental conditions, the heating of anode is insufficient for marked evaporation, and the anode spot formation is associated with the critical flow of fast cathode ions.     

The Effect of External Magnetic Field on a Vacuum Arc

The effect of an external longitudinal magnetic field on the time required for anode spot formation in a high-current (5 to 12 kA) vacuum arc is experimentally studied, and the minimal value of a magnetic field inhibiting the anode spot formation is determined. The experimental results are compared with theory. The phenomenon of break of current in a low-current (100 to 300 A) vacuum discharge upon superposition of a magnetic field with transverse component on the discharge is investigated. The probability of break of current increases with the magnetic field. The possible mechanism of break of current is discussed.     

磁控电弧离子镀阴极斑点特性的高速摄影研究

利用高速摄影技术，对磁控电弧离子镀中阴极斑点大小、寿命及运动轨迹进行了观测，获得了阴极斑点电流密度、运动速度随磁场、电弧电流及背景气体压力改变而变化的关系曲线。     

Control of cathodic arc spot motion under external magnetic field

A closed circular transverse magnetic field is designed to control the spot motion of a cathodic arc on a large rectangular target. Stable and controllable spot motion is observed from both graphite and copper. The arc stability, spot velocity, and etched pattern on the cathode surface are studied systematically. Circular tracks are etched on the target surface by the repetitive spot movement and the surface morphology and resistivity of the cathode materials influence the spot velocity.     

Study of the direct current breakage process in an external nonuniform magnetic field

We study experimentally the influence of an external nonuniform magnetic field with transverse and longitudinal components on the electric characteristics, plasma configuration, and cathode spot arrangement of vaccum-arc discharge. It is revealed that for a cylindrical cathode, cathode spots are nonuniformly distributed on the cathode surface, the spot configuration has no axial symmetry, and the arrangement of spots changes in time depending on the induction value of the external pulsed magnetic field. With an increase in induction, spots (on average) are arranged closer to the cathode, i.e., displaced to the region of weaker transverse field. For two cathode geometries, the probabilities of direct current breakage depending on the induction of the external nonuniform magnetic field are experimentally determined. To determine the conditions of current breakage, a three-dimensional mathematical model of ion motion is suggested and the current breakage criterion is formulated. The trajectories of fast cathode ions in an electrode system with a ring cathode have been calculated using the model. Calculations were performed in a nonuniform magnetic field, the radial and axial components of which have been measured experimentally. It is shown that conditions of current breakage determined with this criterion agree with the results of experiment.     

Study on cathode spot motion and macroparticles reduction in axisymmetric magnetic field-enhanced vacuum arc deposition

Cathode spot motion and macroparticles (MPs) reduction on related films are the two main issues in the application of the vacuum arc deposition (VAD). In the present work, an axisymmetric magnetic field (AMF) was applied to the cathode surface to investigate the influence of the AMF on the cathode spot motion and the MPs reduction on TiN films. The results show that the AMF affected the cathode spot motion by redistributing the dense plasma connected with the initiation of the new spot. With increasing AMF, there is an increasing tendency for the cathode spot to rotate and drift toward the cathode target edge. Based on the results of FEM simulation and the physical mechanism of the cathode spot discharge, the mechanism of the cathode spot motion in the AMF was discussed. The morphology, detailed size distribution, and roughness of the resultant TiN films were systematically investigated. Fewer and smaller MPs ejection is observed with an increase in the transverse component of AMF. The effect of the AMF on the MPs reduction on TiN films was discussed, and the results were compared with the theoretical predictions.     

Effect of tangential magnetic field on ecton processes in cathode spot of vacuum arc

Emission and erosion processes involved in the final stage of the cathode spot cell operation in vacuum arc in the presence of an external magnetic field have been numerically simulated. It is established that the application of a magnetic field leads to asymmetry in the distributions of current density and heat flux, so that their maxima shift in the “anti-Ampere” direction. For more detailed analysis of the phenomenon of retrograde motion of the cathode spot in a magnetic field, it is necessary to study the behavior of a liquid metal phase in the spot.     

Retrograde motion of cathode spots of the first type in a tangential magnetic field

We consider the dynamics of dense plasma of an explosive-electron-emission center—a cell of cathode spot of a vacuum arc in an applied magnetic field. It is established that the explosive expansion of plasma in a transverse magnetic field induces an electric field and an associated current. It is shown that this current initiates the cells of cathode spots of the first type in the direction opposite to the Ampere force action. In this case, the ignition time of a new spot does not exceed a few nanoseconds at a magnetic field of a few kilogauss.     

Stress Intensities Derived from Stresses Around a Spot Weld

The stress intensities (stress intensity factors and J-integral) around a spot weld between sheets of dissimilar materials and different thicknesses are generally expressed by the local stresses around the spot weld. The derivations are established on an interface crack model which represents the radial cross-sections of the spot weld with the local stresses varying from point to point along the periphery of the nugget. The J-integral is determined analytically by applying the equilibrium conditions and the elementary plate theory to the model. The stress intensity factors are then separated by following a load decomposition procedure and an analytic solution to interface cracks. The thermal stress intensities are also obtained for the spot weld. Application examples are given for a tensile-shear specimen. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of axisymmetric two-dimensional magnetic field on the configuration of vacuum-arc plasma

An experimental investigation is made of the effect of axisymmetric two-dimensional magnetic field on the forming of plasma and on the configuration of cathode spots in a vacuum-arc discharge. It is demonstrated that a magnetic field with a transverse (relative to the discharge axis) component has a significant effect on the shape of plasma column and on the rate of expansion of the cathode spot region. In a magnetic field, arc plasma has the form of truncated cone expanding toward the anode. The cathode spots take up a part of the cathode area which decreases with increasing magnetic field. Arguments are given in support of the assumption that the arrangement of cathode spots and the form of arc plasma are defined by the minimum principle similar to the Steinbeck principle. In so doing, the displacement of spots is caused by their emergence in a new region corresponding to a lower arc voltage. Also discussed is the mechanism associated with retrograde motion of cathode spot in view of the effect of azimuthal magnetic field on the axial component of current and of the effect of axial magnetic field on the azimuthal component of current.