科研之友
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摘要
Hydrogen (H-2) discharge plasmas are important tools in plasma processing and provide a relatively simple example of a reactive plasma for basic research. An important parameter that characterizes such plasmas is the hydrogen dissociation rate. However, conventional methods using mass spectrometry to measure depletion in reactive plasmas cannot be applied to H-2 discharges, due to the fast recombination of the dissociation product H atoms on the electrode surfaces. Here, the authors propose a method to measure the dissociation rate in low power discharges by adding a small partial pressure of deuterium (D-2) to the plasma. At such low concentrations, the probability of reforming D-2 is very small. Instead the dissociated D-2 is converted into HD, and thus the change of D-2 partial pressure monitored by a mass spectrometer can give the dissociation rate of D-2, which can then be used to infer the H-2 dissociation rate. Due to differences in the electron collisional dissociation cross section, a correction of the order unity is required to accurately translate the D-2 dissociation rate into an H-2 dissociation rate. The method is used to estimate the H atom density for a 100 mTorr radio-frequency plasma as a function of discharge power. Published by the AVS.
- 出版日期2018-5
