微阴极电弧推力器导电薄膜状态实验研究

Experimental Study on Conductive Film State of Micro-Cathode Arc Thruster

为填补微阴极电弧推力器(Micro Cathode Arc Thruster,μCAT)导电薄膜状态有效评估手段的缺失,深入研究导电薄膜退化规律,本文基于四探针电阻率测试理论和尺寸效应拟合模型,建立了μCAT推力器导电薄膜状态表征方法,运用该方法探究了不同放电次数下样机薄膜参数的变化规律。研究表明随着放电次数的增加,薄膜电阻率上升,薄膜特征厚度减小,受二者变化的影响,薄膜电阻呈现指数上升趋势,其中厚度变化的影响大于电阻率的影响。对于金属Ti薄膜,块状电阻区和尺寸效应区的分界线在2μm左右,厚度大于5μm时推力器会由于短路失效,厚度处于0.012~2μm时为推力器的稳定放电区,这一区域处于尺寸效应区且电阻持续上升,当厚度小于0.012μm时薄膜电阻超过1000Ω并急剧上升直至推力器断路失效。导电薄膜状态评估方法是将实验测量数据和理论模型相结合计算得到导电薄膜的状态参数,通过实验验证了其有效性,可以为未来通过导电薄膜状态表征来评估μCAT寿命提供技术支持。

In order to make up for the lack of evaluation methods for conductive films of Micro Cathode Arc Thruster(μCAT)and in-depth study the degradation of film,a state characterization method of the conductive film was established,based on the four-probe resistivity test theory and size effect fitting model.This method is used to investigate the variation of the conductive film parameters ofμCAT under different discharge times.The research shows that with the increase of the number of discharges,the resistivity of the film increases,the charac⁃teristic thickness of the film decreases.Influenced by the changes of the two factors,the resistance of the film in⁃creases exponentially,and the influence of the thickness is greater than that of the resistivity.For Ti films,the di⁃viding line between the bulk resistance region and the size effect region is about 2μm.When the thickness is greater than 5μm,the thruster will fail due to short circuit.When the thickness is between 0.012μm and 2μm,it is the stable discharge region of the thruster,which is in the size effect region and the resistance continues to rise.When the thickness is less than 0.012μm,the film resistance exceeds 1000Ωand rises sharply until the thruster fails due to open circuit.The state evaluation method of conductive film is to calculate the parameters of conduc⁃tive film by combining experimental measurement data and theoretical model,and the validity of the method is verified by experiments.This method can provide technical support for the future evaluation of the lifetime ofμCAT by the state characterization of the conductive film.