Zhou Jie, Fisher Ellen R
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA.
J Phys Chem B. 2006 Nov 2;110(43):21911-9. doi: 10.1021/jp064125n.
The surface reactivity of CH radicals was measured during plasma deposition of hydrogenated diamondlike carbon (DLC) films using the imaging of radicals interacting with surfaces (IRIS) method. In this technique, spatially resolved laser-induced fluorescence (LIF) is used to determine surface reactivity, R, of plasma species. The measured reactivity of CH is near unity and shows no dependence on the applied rf power (P), argon fraction, substrate temperature, or substrate bias. Kinetic translational temperatures, (T), of CH in the molecular beam were also measured. Modeling of the kinetic data yields ThetaT(CH) values of approximately 2200-2500 K and 1600-1700 K for CH4/Ar plasmas at pressures of 50 and 110 mTorr, respectively, with no clear dependence on the argon fraction (at P = 100 W). The average ThetaT(CH) does, however, change with P, (T) = approximately 2050-9050 K, over the range P = 180-20 W. These results indicate that ThetaT(CH) is associated with the electron temperature in the plasma. The rotational temperature, (R), determined from the CH rotational excitation spectrum is approximately 1450 K with no clear dependence on P or the Ar fraction in the feed. The difference between ThetaT(CH) and ThetaR(CH) can be explained by the different relaxation rates after the dissociation of CH4 by electron impact.
在使用自由基与表面相互作用成像（IRIS）方法进行氢化类金刚石碳（DLC）薄膜的等离子体沉积过程中，对CH自由基的表面反应性进行了测量。在该技术中，空间分辨激光诱导荧光（LIF）用于确定等离子体物种的表面反应性R。所测得的CH反应性接近1，且不依赖于所施加的射频功率（P）、氩气分数、衬底温度或衬底偏压。还测量了分子束中CH的动力学平移温度（T）。对动力学数据进行建模得出，在50和110 mTorr压力下，CH4/Ar等离子体的ThetaT(CH)值分别约为2200 - 2500 K和1600 - 1700 K，且在氩气分数方面没有明显依赖性（在P = 100 W时）。然而，平均ThetaT(CH)确实会随着P变化，在P = 180 - 20 W范围内，（T）约为2050 - 9050 K。这些结果表明ThetaT(CH)与等离子体中的电子温度相关。由CH转动激发光谱确定的转动温度（R）约为1450 K，且对P或进料中的Ar分数没有明显依赖性。ThetaT(CH)和ThetaR(CH)之间的差异可以通过电子碰撞使CH4解离后的不同弛豫速率来解释。
