Electron energy distribution function in DC magnetron axially symmetric discharges: evidence of spatial anisotropy
Electron energy distribution function in DC magnetron axially symmetric discharges: evidence of spatial anisotropy
复制标题
直流磁控管轴对称放电中的电子能量分布函数：空间各向异性的证据
DOI：
10.1088/0022-3727/27/2/016
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
J. Sundgren
中科院分区：
文献类型：
--
作者：
I. Ivanov;P. Kazansky;L. Hultman;J. Sundgren
在轴对称磁控溅射气体放电等离子体中进行探针电流 i 与探针电压 v 的二阶导数 d2i/dv2 的实验测量，以确定电子能量分布函数。使用圆柱形朗缪尔探针进行测量，该探针沿放电轴和横向于两个方向。实验在 3 mTorr 的恒定氩气压力和 1 A 的恒定放电电流下对钼阴极进行。研究了放电区域的三种不同磁场配置，这些配置是通过在原始磁控管磁场上叠加外部磁场来实现的。通过改变磁场分布，特别是改变探头位置处磁感应强度 Bz 的相应轴向分量，二阶导数 d2i/dv2 显着改变。当探头沿径向和轴向方向定向时，d2i/dv2 也存在一定差异。因此，对于相对的叠加磁场（Bz = -31 G），发现了电子能量分布函数的球形空间等离子体各向同性，而对于原始（Bz = 36 G）和支撑（Bz = 103 G）磁场配置，则建立了等离子体各向异性。通过比较三种磁场配置中每一种所评估的各自平均电子能（E）来量化各向异性程度。研究发现，在确定电子能量分布函数过程中假设球面各向同性会导致在所用实验条件下对 (E) 的估计高达 10%。
Experimental measurements of the second derivative d2i/dv2 of the probe current i versus probe voltage v were performed in an axially symmetric magnetron sputtering gas discharge plasma in order to determine the electron energy distribution function. The measurements were performed using a cylindrical Langmuir probe oriented in two directions, along and across the discharge axis. The experiments were carried out at a constant argon gas pressure of 3 mTorr and at a constant discharge current of 1 A to a molybdenum cathode. Three different magnetic field configurations in the discharge region were investigated and these were achieved by superimposing an external magnetic field on the original magnetron magnetic field. By varying the magnetic field distribution and, in particular, the respective axial component of the magnetic induction Bz at the probe position, the second derivative d2i/dv2 was significantly altered. Certain differences in d2i/dv2 were also established with the probe oriented in radial and axial directions. A spherical spatial plasma isotropy of the electron energy distribution function was thus found for the opposed superimposed magnetic field (Bz=-31 G) while for both the original (Bz=36 G) and the supporting (Bz=103 G) magnetic field configurations, a plasma anisotropy was established. The degree of anisotropy was quantified by comparison of the respective average electron energies (E) evaluated for each of the three magnetic field configurations. It was found that assumption of spherical isotropy during determination of the electron energy distribution function leads to overestimation of (E) by up to 10% under the experimental conditions used.