溅射功率对磁控溅射法制备MgF2薄膜组织和性能的影响

为了减少磁控溅射法沉积MgF₂薄膜的F贫乏缺陷, 在工作气体Ar₂中加入SF₆作为反应气体, 在石英玻璃衬底上用射频磁控溅射法制备了MgF₂薄膜, 研究了溅射功率对MgF₂薄膜化学成分、微观结构和光学性能的影响。结果表明, 随着溅射功率从115 W增加到220 W, F: Mg的原子比不断增加, 185 W时达到2.02, 最接近理想化学计量比2 : 1;薄膜的结晶度先提高后降低, 最后转变为非晶态; MgF₂薄膜的颗粒尺寸先是有所增加, 轮廓也变得更加清晰, 最后又变得模糊。MgF₂薄膜的折射率先减小后增大, 在185 W时获得最低值, 550 nm波长的折射率1.384非常接近MgF₂块体晶体;镀膜玻璃在300~1100 nm范围内的透光率(以下简称薄膜透光率)先增大后减小, 185 W时达到94.99%, 比玻璃基底的透光率高出1.79%。

Sputtering Power on the Microstructure and Properties of MgF2 Thin Films Prepared with Magnetron Sputtering

To reduce the F deficiency defect in MgF₂ thin films deposited with magnetron sputtering, SF₆ was added to the working gas Ar₂ as the reactive gas, and MgF₂ thin films were prepared on quartz glass substrates with radio frequency (RF) magnetron sputtering. The effects of sputtering power on the chemical compositions, microstructure and optical properties of MgF₂ thin film were investigated. The results show that with sputtering power increase from 115 to 220 W, the atomic ratio of F to Mg increased continuously, and reached 2.02 at 185 W, close to ideal stoichiometric ratio of 2: 1. The crystallinity of MgF₂ film improved first, then decreased, and finally changed into amorphous state. Profile of particles composing MgF₂ film became clearer at first, and finally became blurred. Refractive index of MgF₂ film decreased firstly and then increased, and got the lowest value at 185 W, 1.384 at 550 nm wavelength which is very close to that of MgF₂ bulk crystal. The integral transmittance of the coated glass within 300-1100 nm (hereinafter referred to as the transmittance of the thin film) increased first and then decreased, and reached 94.99% at 185 W, higher than that of the bare glass substrate by 1.79%.