Characterization of high density matrix microwave argon plasmas by laser absorption and electric probe diagnostics
Characterization of high density matrix microwave argon plasmas by laser absorption and electric probe diagnostics
复制标题
通过激光吸收和电探针诊断表征高密度矩阵微波氩等离子体
DOI：
10.1088/0022-3727/40/17/024
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
J. Pelletier
中科院分区：
文献类型：
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作者：
L. Latrasse;N. Sadeghi;A. Lacoste;A. Bes;J. Pelletier
在100 Pa压力范围内，分布在平面矩阵结构上的微波等离子体源可以产生无磁场的均匀二维等离子体。在氩气中，离子密度在1012到1013 cm−3之间，微波功率在0.4到2 kW之间，已经获得了这种均匀的等离子体片。用圆柱形朗缪尔探针研究了等离子体的电特性。第一个特征与等离子体势有关，由于电子温度向微波电场施加的源平面大幅增加，等离子体势显示出相当高的值。其次，随着微波功率的增加，观察到的电子温度的降低可以通过Ar原子的亚稳态和高激发态的多步电离机制的出现来证明。用激光二极管吸收光谱法测定了Ar（3P2）亚稳态态的浓度和温度。结果表明，在距离源面2 cm处存在明显的Ar（3P2）亚稳态，浓度和温度随氩气压力和微波功率的变化范围分别为1010 ~ 1011 cm−3和500 ~ 1300 K。采用几个简化假设的解析模型提供了与实验结果很一致的等离子体图像。
Microwave plasma sources distributed on a planar matrix configuration can produce uniform bi-dimensional plasmas free from magnetic field in the 100 Pa pressure range. In argon, such uniform sheets of plasma have been obtained with ion densities in the range of 1012 to 1013 cm−3 with microwave power ranging from 0.4 to 2 kW. The electrical characterization of the plasma has been investigated using a cylindrical Langmuir probe. A first feature concerns the plasma potential that exhibits quite high values due to the large increase in the electron temperature towards the source plane where the microwave electric field is applied. Secondly, the decrease in the electron temperature observed when increasing the microwave power can be justified by the apparition of multi-step ionization mechanisms via metastable and higher excited states of Ar atom. The concentration and temperature of Ar(3P2) metastables have been measured by laser diode absorption spectroscopy. The results indicate that the presence of Ar(3P2) metastables is significant at 2 cm from the source plane with concentration and temperature values varying from 1010 to 1011 cm−3 and from 500 K to 1300 K, respectively, as functions of argon pressure and microwave power. An analytical model using a few simplifying assumptions provides a plasma picture in good agreement with the experimental results.