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首页> 外文期刊>Plasma Sources Science & Technology >N_2-H_2 capacitively coupled radio-frequency discharges at low pressure. Part I. Experimental results: effect of the H_2 amount on electrons, positive ions and ammonia formation
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N_2-H_2 capacitively coupled radio-frequency discharges at low pressure. Part I. Experimental results: effect of the H_2 amount on electrons, positive ions and ammonia formation

机译：N_2-H_2电容耦合低压的射频放电。 第一部分。实验结果：H_2量对电子，正离子和氨形成的影响

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The mixing of N_2 with H_2 leads to very different plasmas from pure N_2 and H_2 plasma discharges. Numerous issues are therefore raised involving the processes leading to ammonia (NH_3) formation. The aim of this work is to better characterize capacitively-coupled radiofrequency plasma discharges in N_2 with few percents of H_2 (up to 5%), at lowpressure (0.3-1 mbar) and low coupled power (3-13W). Both experimental measurements and numerical simulations are performed. For clarity, we separated the results in two complementary parts. The actual one (first part), presents the details on the experimental measurements, while the second focuses on the simulation, a hybrid model combining a 2D fluid module and a 0D kinetic module. Electron density is measured by a resonant cavity method. It varies from 0.4 to 5 ×10~9 cm~(-3), corresponding to ionization degrees from 2 ×10~(-8) to 4 ×10~(-7). Ammonia density is quantified by combining IR absorption and mass spectrometry. It increases linearly with the amount of H_2 (up to 3 ×10~(13) cm~(-3) at 5% H_2). On the contrary, it is constant with pressure, which suggests the dominance of surface processes on the formation of ammonia. Positive ions are measured by mass spectrometry. Nitrogen-bearing ions are hydrogenated by the injection of H_2, N_2H~+ being the major ion as soon as the amount of H_2 is >1%. The increase of pressure leads to an increase of secondary ions formed by ion/radical-neutral collisions (ex: N_2H~+, NH~4 ~+, H_3 ~+), while an increase of the coupled power favours ions formed by direct ionization (ex: N_2 ~+, NH_3 ~+, H_2 ~+).
机译：N_2与H_2的混合导致了与纯N_2和H_2等离子体放电截然不同的等离子体。因此，涉及导致氨（NH_3）生成的过程的许多问题被提出。这项工作的目的是更好地描述在低压（0.3-1毫巴）和低耦合功率（3-13W）条件下，含少量H_2（高达5%）的N_2中的电容耦合射频等离子体放电。进行了实验测量和数值模拟。为了清晰起见，我们将结果分为两个互补部分。实际模型（第一部分）介绍了实验测量的细节，而第二部分则侧重于模拟，这是一个结合了2D流体模块和0D动力学模块的混合模型。用谐振腔法测量电子密度。其变化范围为0.4～5×10~9cm-3，对应的电离度为2×10-8～4×10-7。氨浓度通过红外吸收和质谱相结合的方法进行量化。随着h2含量的增加（当h2含量为5%时，最大可达3×10~（13）cm-3），其浓度呈线性增加。相反，它与压力成常数，这表明表面过程对氨的形成起主导作用。正离子通过质谱法测量。含氮离子通过注入H_2进行氢化，当H_2的含量大于1%时，N_2H~+为主要离子。压力的增加导致离子/自由基中性碰撞形成的二次离子（ex:N_2H+，NH~4+，H_3+）增加，而耦合功率的增加有利于直接电离形成的离子（ex:N_2+，NH_3+，H_2+）。

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