A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparis...A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparison with a traditional tungsten emissive probe,including the operating temperature,the electron emission capability and the plasma potential measurement.Studies of the operating temperature and electron emission capability show that the tungsten emissive probe usually works at a temperature of 1800 K-2200 K while the oxide cathode emissive probe can function at about 1200 K-1400 K.In addition,plasma potential measurements using the oxide cathode emissive probe with different techniques have been accomplished in microwave electron cyclotron resonance plasmas with different discharge powers.It is found that a reliable plasma potential can be obtained using the improved inflection point method and the hot probe with zero emission limit method,while the floating point method is invalid for the oxide cathode emissive probe.展开更多
We have developed an automatic emissive probe apparatus based on the improved inflection point method of the emissive probe for accurate measurements of both plasma potential and vacuum space potential.The apparatus c...We have developed an automatic emissive probe apparatus based on the improved inflection point method of the emissive probe for accurate measurements of both plasma potential and vacuum space potential.The apparatus consists of a computer controlled data acquisition card,a working circuit composed by a biasing unit and a heating unit,as well as an emissive probe.With the set parameters of the probe scanning bias,the probe heating current and the fitting range,the apparatus can automatically execute the improved inflection point method and give the measured result.The validity of the automatic emissive probe apparatus is demonstrated in a test measurement of vacuum potential distribution between two parallel plates,showing an excellent accuracy of 0.1 V.Plasma potential was also measured,exhibiting high efficiency and convenient use of the apparatus for space potential measurements.展开更多
Conventional Langmuir probe techniques usually face the difficulty of being used in processing plasmas where dielectric compounds form,due to rapid failure by surface insulation.A solution to the problem,the so-called...Conventional Langmuir probe techniques usually face the difficulty of being used in processing plasmas where dielectric compounds form,due to rapid failure by surface insulation.A solution to the problem,the so-called harmonic probe technique,had been proposed and shown effectiveness.In this study,the technique was investigated in detail by changing bias signal amplitudes V_0,and evaluated its accuracy by comparing with the conventional Langmuir probe.It was found that the measured electron temperature Teincreased with V_0,but showing a relatively stable region when V_0〉Te/e in which it was close to the true Tevalue.This is contrary to the general consideration that V_0should be smaller than Te/e for accurate measurement of Te.The phenomenon is interpreted by the non-negligible change of the ion current with V_0at low V_0values.On the other hand,the measured nialso increased with V_0due to the sheath expansion,and to improve the accuracy of niit needs to linearly extrapolate the ni-V_0trend to V_0=0.The results were applied to a diagnosis of the plasmas for chemical vapor deposition of diamond-like carbon thin films and the relationship between plasma parameters and films deposition rates was obtained.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.11905076)S&T Program of Hebei (Grant No.SZX2020034)。
文摘A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparison with a traditional tungsten emissive probe,including the operating temperature,the electron emission capability and the plasma potential measurement.Studies of the operating temperature and electron emission capability show that the tungsten emissive probe usually works at a temperature of 1800 K-2200 K while the oxide cathode emissive probe can function at about 1200 K-1400 K.In addition,plasma potential measurements using the oxide cathode emissive probe with different techniques have been accomplished in microwave electron cyclotron resonance plasmas with different discharge powers.It is found that a reliable plasma potential can be obtained using the improved inflection point method and the hot probe with zero emission limit method,while the floating point method is invalid for the oxide cathode emissive probe.
基金supported by National Natural Science Foundation of China(No.11675039)
文摘We have developed an automatic emissive probe apparatus based on the improved inflection point method of the emissive probe for accurate measurements of both plasma potential and vacuum space potential.The apparatus consists of a computer controlled data acquisition card,a working circuit composed by a biasing unit and a heating unit,as well as an emissive probe.With the set parameters of the probe scanning bias,the probe heating current and the fitting range,the apparatus can automatically execute the improved inflection point method and give the measured result.The validity of the automatic emissive probe apparatus is demonstrated in a test measurement of vacuum potential distribution between two parallel plates,showing an excellent accuracy of 0.1 V.Plasma potential was also measured,exhibiting high efficiency and convenient use of the apparatus for space potential measurements.
文摘Conventional Langmuir probe techniques usually face the difficulty of being used in processing plasmas where dielectric compounds form,due to rapid failure by surface insulation.A solution to the problem,the so-called harmonic probe technique,had been proposed and shown effectiveness.In this study,the technique was investigated in detail by changing bias signal amplitudes V_0,and evaluated its accuracy by comparing with the conventional Langmuir probe.It was found that the measured electron temperature Teincreased with V_0,but showing a relatively stable region when V_0〉Te/e in which it was close to the true Tevalue.This is contrary to the general consideration that V_0should be smaller than Te/e for accurate measurement of Te.The phenomenon is interpreted by the non-negligible change of the ion current with V_0at low V_0values.On the other hand,the measured nialso increased with V_0due to the sheath expansion,and to improve the accuracy of niit needs to linearly extrapolate the ni-V_0trend to V_0=0.The results were applied to a diagnosis of the plasmas for chemical vapor deposition of diamond-like carbon thin films and the relationship between plasma parameters and films deposition rates was obtained.
