Reactive Radical Etching of Quartz by Microwave Activated CH4/H2 Plasmas Promotes Gas Phase Nanoparticle Formation

IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL
Michael N. R. Ashfold*, Basile F. E. Curchod, Daniel Hollas, Jie Ma and Yuri A. Mankelevich*, 
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Abstract

An attenuation of visible probe radiation identified in earlier absorption studies of microwave plasma-activated CH4/H2/Ar gas mixtures is shown to arise from nanoparticles in under-pumped regions on opposing sides of a reactor used for diamond chemical vapor deposition. The present modeling studies highlight (i) ejection of Si-containing species into the gas phase by reactive radical etching of the quartz window through which the microwave radiation enters the reactor, enabled by suitably high window temperatures (TSiO2) and the synergistic action of near-window H atoms and CyHx radicals; (ii) subsequent processing of the ejected material, some of which are transported to and accumulate in stagnation regions in the entrance to the reactor side arms; and (iii) the importance of Si in facilitating homogeneous gas phase nucleation, clustering, and nanoparticle growth in these regions. The observed attenuation, its probe wavelength dependence, and its variations with changes in process conditions can all be rationalized by a combination of absorption and scattering contributions from Si/C/H containing nanoparticles with diameters d in the range of 50–100 nm. Possible implications for Si incorporation in CVD diamond samples are discussed.

微波活化CH4/H2等离子体反应自由基蚀刻石英促进气相纳米颗粒的形成
在早期对微波等离子体激活的CH4/H2/Ar气体混合物的吸收研究中发现,可见探针辐射的衰减是由用于金刚石化学气相沉积的反应器两侧欠泵区域的纳米颗粒引起的。目前的建模研究强调(i)通过反应自由基蚀刻石英窗口将含硅物质喷射到气相,微波辐射通过石英窗口进入反应器,通过适当的高窗口温度(TSiO2)和近窗口H原子和CyHx自由基的协同作用实现;(ii)喷射材料的后续处理,其中一些被输送到反应堆侧臂入口的停滞区并在该停滞区积累;(iii)硅在促进这些区域的均匀气相成核、聚类和纳米颗粒生长方面的重要性。直径d在50-100 nm范围内的含Si/C/H纳米颗粒的吸收和散射贡献可以解释所观察到的衰减、其对探针波长的依赖以及其随工艺条件变化的变化。讨论了CVD金刚石样品中Si掺入的可能含义。
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来源期刊
The Journal of Physical Chemistry A
The Journal of Physical Chemistry A 化学-物理:原子、分子和化学物理
CiteScore
5.20
自引率
10.30%
发文量
922
审稿时长
1.3 months
期刊介绍: The Journal of Physical Chemistry A is devoted to reporting new and original experimental and theoretical basic research of interest to physical chemists, biophysical chemists, and chemical physicists.
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