Modeling of Atmospheric Pressure Glow Discharge Plasmas in Nitrogen-Oxygen Mixtures
Modeling of Atmospheric Pressure Glow Discharge Plasmas in Nitrogen-Oxygen Mixtures
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氮氧混合物中大气压辉光放电等离子体的模拟
DOI：
10.1541/ieejfms.127.423
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发表时间：
2007
影响因子：
--
通讯作者：
A. Saito
中科院分区：
文献类型：
--
作者：
E. Suetomi;T. Mizukoshi;K. Fukazawa;A. Saito
大气压辉光放电（APGD）等离子体具有处理速率高、不需要真空系统等优点，在材料表面处理和化学气相沉积（CVD）等领域具有广泛的应用前景。氮气由于与其它放电气体相比成本低而被用作放电气体。放电气体通常与氧混合以获得作为反应性自由基的氧原子。本文建立了氮氧混合气体中APGD等离子体的一维模型。在100 kHz的频率下，进行了氧混合物对激发的氮分子和氧原子的影响的调查。光学发射光谱（OES）测量进行评估模型的有效性。该模型基于一维粒子连续性方程和Poisson方程，考虑了气相反应中的电子-中性、离子-中性和中性-中性碰撞。本研究的基本假设如下：（1）考虑一维平行板电极结构。(2)电子通量和离子通量由漂移扩散近似描述。(3)忽略了气流的影响。(4)由于电子能量方程的解不能收敛，因此在本计算中忽略了电子能量守恒方程。(5)省略了离子能量守恒方程。假设离子能量为0.026 eV。(6)电子迁移率，扩散系数和反应速率系数的玻尔兹曼方程作为局部电场的函数的数值分析确定。考虑了八种基态物种N，N2，O，O2，O3，NO，NO2，N2 O，八种离子N，N2，N3，N4，O，O，O2，O2，四种亚稳态物种N2（A ~ u），N2（a ~ u），O（D），O2（a ~ g）和三种辐射态物种N2（B ~ g），N2（C ~ u），NO（A ~ g）。APGD等离子体是在两个被介质阻挡层覆盖的平面电极之间产生的。施加的正弦电压幅度为5 kV，频率为100 kHz。光谱仪是一台单色仪，配备600线mm光栅，并耦合到2048元线硅CCD阵列。图1示出了作为氧混合物浓度的函数的通过OES计算出的N2（C = Cu）密度（实线）和N2 SPS的光发射强度（实心圆）。计算的密度和测量的光发射强度都随着氧混合物的增加而急剧下降。图2示出了作为氧混合物浓度的函数的通过OES计算的NO（A）密度（实线）和NO-γ系统的光发射强度（实心圆）。与图1相反，NO的发射强度首先在氧混合物的0.2%左右达到峰值，然后下降。计算的密度和测量的NO发射强度都在氧浓度的0.2%附近有一个峰值。用该模型计算的N2（C u）和NO（A u）密度分别与SPS和NO-γ系统的观测发射强度具有相似的趋势。0 10 20 0 1 2 3 4 [×10]
Application of atmospheric pressure glow discharge (APGD) plasmas to materials processing such as surface treatment and chemical vapor deposition (CVD) is very atStractive, since the APGD plasmas have a potential of high treatment rate and require no vacuum systems. Nitrogen gas has been used as discharge gas due to low cost compared to other discharge gases. The discharge gas is often admixed with oxygen in order to obtain oxygen atom which is reactive radical. In the present study, a one-dimensional model for the APGD plasmas in the nitrogen-oxygen mixtures is constructed. The investigation of the influence of the oxygen admixture to the excited nitrogen molecules and oxygen atoms at a frequency 100 kHz is performed. Optical emission spectroscopy (OES) measurements are performed to evaluate the validity of the model. The model is based on the one-dimensional particle continuity equations coupled with Poisson's equation and on the gas phase reactions which consist of the electron-neutral, ion-neutral and neutral-neutral collisions. The basic assumptions in the present study are as follows: (1) A one-dimensional parallel-plate electrode configuration is considered. (2) The electron flux and ion flux are described by a drift-diffusion approximation. (3) The effect of gas flow is omitted. (4) The electron energy equation had a serious drawback for the present calculation since solution of the equation failed to converge, and therefore electron energy conservation equations is omitted. (5) Ion energy conservation equations is omitted. The ion energy is assumed to be 0.026 eV. (6) The electron mobility, diffusion coefficient and reaction rate coefficient were determined from numerical analysis of the Boltzmann equation as a function of the local electric field. Eight ground state species, N, N2, O, O2, O3, NO, NO2, N2O, eight ions N, N2, N3, N4, O, O, O2, O2, four metastable sate species, N2(AΣu), N2(a’Σu), O(D), O2(a∆g) and three radiative state species N2(BΠg), N2(CΠu), NO(AΣ) are taken into account. APGD plasma is obtained between two plane electrodes covered by dielectric barrier. Amplitude of applied sinusoidal voltage is 5 kV and frequency is 100 kHz. The optical spectrometer is a monochromator equipped with 600 lines mm gratings and coupled to a 2048-element linear silicon CCD array. Figure 1 shows calculated N2(CΠu) density (solid line) and optical emission intensity of N2 SPS by OES (full circles) as a function of the concentration of oxygen admixture. Both the calculated density and the measured optical emission intensity decrease steeply with increasing oxygen admixture. Figure 2 shows calculated NO(AΣ) density (solid line) and optical emission intensity of NO-γ system by the OES (full circles) as a function of the concentration of oxygen admixture. In contrast to Fig.1, the emission intensity of NO first peaks at around 0.2 % of oxygen admixture and then decreases. Both the calculated density and the measured emission intensity of NO have a peak around 0.2 % of oxygen concentration. The densities of N2(CΠu) and NO(AΣ) calculated by the model show trends similar to the observed emission intensities of the SPS and NO-γ system, respectively. 0 10 20 0 1 2 3 4 [×10]