Determination of gas temperature and C2 absolute density in Ar/H2/CH4 microwave discharges used for nanocrystalline diamond deposition from the C2 Mulliken system
Determination of gas temperature and C2 absolute density in Ar/H2/CH4 microwave discharges used for nanocrystalline diamond deposition from the C2 Mulliken system
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通过 C2 Mulliken 系统测定用于纳米晶金刚石沉积的 Ar/H2/CH4 微波放电中的气体温度和 C2 绝对密度
DOI：
10.1088/0963-0252/13/3/003
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
A. Gicquel
中科院分区：
文献类型：
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作者：
G. Lombardi;F. Bénédic;F. Mohasseb;K. Hassouni;A. Gicquel
报道了微波等离子体辅助化学气相沉积法合成纳米金刚石的Ar/H2/CH 4放电光谱特性。实验是在一个中压钟罩反应器中实现的，在那里使用微波腔耦合系统点燃放电。CH 4的浓度保持在1%，并且在200毫巴的压力下，氢浓度/微波功率（MWP）的耦合组的范围为2%/500 W至7%/800 W。对Mulliken系统和C2（d3 g-a3 u）Swan系统进行了发射光谱和宽带吸收光谱研究，以确定等离子体中的气体温度和C2绝对密度。为了这个目的，因为天鹅系统是相当有名的，非常重要的是致力于实现一个详细的模拟的Mulliken系统，它允许确定的旋转温度和密度的基态，以及旋转温度的状态，从实验数据。所有的实验值进行了比较，预测的热化学模型来描述Ar/H2/CH 4微波放电准均匀等离子体假设下。该比较显示了从C2 Mulliken系统测量的值、从C2 Swan系统测量的值和从等离子体建模计算的值之间的合理一致性，特别是在低氢浓度/MWP下。这些一致的结果表明，使用的Mulliken系统导致相当好的气体温度和C2的绝对密度的估计。对于所研究的条件发现的相对高的气体温度，通常在3000 K和4000 K之间，归因于氩气的低导热性，其可以限制基板表面和反应器壁的热损失。根据实验条件，测得的C2绝对密度范围为1013至1014 cm−3。这些高值可能是由于高气体温度引起的烃类物质的增强的热转化而产生的。
The spectroscopic characterization of Ar/H2/CH4 discharges suitable for the synthesis of nanocrystalline diamond using the microwave plasma assisted chemical vapour deposition process is reported. The experiments are realized in a moderate-pressure bell jar reactor, where discharges are ignited using a microwave cavity coupling system. The concentration of CH4 is maintained at 1% and the coupled set of hydrogen concentration/microwave power (MWP) ranges from 2%/500 W to 7%/800 W at a pressure of 200 mbar. Emission spectroscopy and broadband absorption spectroscopy studies are carried out on the Mulliken system and the C2(d 3Πg–a 3Πu) Swan system in order to determine the gas temperature and the C2 absolute density within the plasma. For this purpose, and since the Swan system is quite well-known, much importance is devoted to the achievement of a detailed simulation of the Mulliken system, which allows the determination of both the rotational temperature and the density of the ground state, as well as the rotational temperature of the state, from experimental data. All the experimental values are compared to those predicted by a thermochemical model developed to describe Ar/H2/CH4 microwave discharges under quasi-homogeneous plasma assumption. This comparison shows a reasonable agreement between the values measured from the C2 Mulliken system, those measured from the C2 Swan system and that calculated from plasma modelling, especially at low hydrogen concentration/MWP. These consistent results show that the use of the Mulliken system leads to fairly good estimates of the gas temperature and of the C2 absolute density. The relatively high gas temperatures found for the conditions investigated, typically between 3000 K and 4000 K, are attributed to the low thermal conductivity of argon that may limit thermal losses to the substrate surface and reactor wall. The measured C2 absolute densities range from 1013 to 1014 cm−3 depending on the experimental conditions. These high values may result from an enhanced thermal conversion of hydrocarbon species due to the high gas temperature.