CH_4或CH_4+Ar介质阻挡放电中的离子能量和类金刚石膜制备  

Deposition of diamond-like carbon and analysis of ion energy in CH_4 or CH_4+Ar dielectric barrier discharge plasma

作　　者：刘艳红[1] 张家良[1] 王卫国[2] 李建[1] 刘东平[1] 马腾才[1] 

机构地区：[1]大连理工大学三束材料改性国家重点实验室,大连116024 [2]大连理工大学等离子体物理化学研究室,大连116024

出　　处：《物理学报》2006年第3期1458-1463,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:50002002)资助的课题.~~

摘　　要：实验上,利用纯CH4及CH4+Ar在几百帕量级气压下的介质阻挡放电制备类金刚石膜,研究了气压p与放电间隙d乘积(pd值)以及Ar的体积百分比RAr对膜硬度的影响.理论上,从离子与气体分子的双体碰撞出发,利用较高折合电场强度E/n(电场强度与粒子数密度之比)下离子及中性粒子速度分布的双温模型、离子在其他气体中运动时遵守的朗之万方程及离子在混合气体中运动时遵守的布兰克法则,对CH4+和Ar+离子能量进行了分析.结果表明:1)CH4介质阻挡放电中,pd值由1·862×103Pa mm降低至2·66×102Pa mm时,CH4+能量由5·4eV增加到163eV,类金刚石膜硬度由2·1GPa提高到17·6GPa;2)保持总气压p=100Pa,放电间距d=5mm不变,在CH4中加入Ar气,当RAr由20%增加至83%时,CH4+的能量由69eV增加到92eV,而Ar+能量由93eV降低至72eV.虽然CH4+能量增加有助于提高沉积膜硬度,但当RAr大于67%,高强度Ar+轰击会导致膜表面石墨化,膜硬度降低.为了验证离子能量理论模型的正确性,实验测量了H2介质阻挡放电中离子能量,测量结果与理论计算之间最大相对误差为16%.Diamond-like carbon （DLC） films were deposited by dielectric barrier discharge （DBD） from CH4 or CH4 ＋ Ar at pressure of several hundred Pa. The dependence of the film hardness on the product of p and d （p is the gas pressure and the d is the discharge space） and Ar volume concentration （RAt） was investigated experimentally. The kinetic energies of CH4^＋ and Ar^＋ ions were analyzed theoretically based on the two-temperature model for high reduced field E/ n （ the ratio of electric field strength to the gas number density）, in which ions were assigned a temperature much higher than the gas temperature, on the Langevin equation in other gas and on the Blanc law in mixed gases. The results showed that, 1 ） for CH4 DBD, when decreasing pd from 1.862 × 10^3Pa mm to 2.66 × 10^2Pa mm, the kinetic energy of CH4＋ increases from 5.4 to 163eV, while the hardness of deposited DLC films increases from 2.1 to 17.6 GPa. 2） For CH4^＋ Ar DBD, when increasing Ar volume concentration from 20% to 83%, the kinetic energy of CH4^＋ increases from 69 to 92eV, whereas the kinetic energy of Ar^＋ decreases from 93 to 72eV. The increase of film hardness with increasing Ar volume concentration up to 67 % can be attributed to the increase of CH4^＋ kinetic energy. However, the impinging of energetic Ar^＋ on the film surface reduces the film hardness owing to graphitization. For verification of the theoretical model on ion energy analysis, the kinetic energy of ions in H2 DBD were measured and compared with that from theoretical analysis.

关 键 词：离子能量 介质阻挡放电 类金刚石膜 

分 类 号：O461.2[理学—电子物理学]