疏水性对溶胶-凝胶SiO2薄膜抗真空污染及抗激光损伤能力的影响

以正硅酸乙酯作为前驱体,利用碱催化方式制备了SiO2溶胶,通过在溶胶中添加含疏水基团(-CH3)的六甲基二硅氮烷(HMDS)对溶胶进行改性,使用添加不同物质的量比HMDS改性后的溶胶用提拉法在K9基片上镀膜,获得了具有疏水性能的SiO2薄膜。采用自制接触角测量仪、紫外-可见-近红外分光光度计研究了薄膜的水接触角和透过率。测试了薄膜的激光损伤阈值,并观察了激光辐照后薄膜的损伤形貌。通过真空污染实验对薄膜的抗污染能力及抗激光损伤能力进行了研究。实验结果表明:经疏水改性的溶胶所镀制的薄膜激光损伤阈值由未改性样品的24.3 J·cm-2增加到37 J·cm-2(1 064 nm,10 ns),且抗真空污染能力大大加强:在真空环境下保存168 h后,未改性样品的峰值透过率下降了2%,而疏水改性后的样品峰值透过率仅下降了0.25%,并保持了较高的激光损伤阈值(30.8 J·cm-2)。

Effect of Hydrophobicity on the Vacuum-Contamination Resistance and Laser Damage Threshold of Sol-Gel Silica Coating

Silica antireflective coatings modified by hexamethyldisilazane (HMDS) were deposited on clean substrates by sol-gel process. The effects of HMDS on the contamination resistant capability and laser-induced damage threshold (LIDT) of coatings were investigated. With the modified sol the resultant coatings were hydrophobic and the contact angle for water increased with the increasing amount of HMDS in the reaction mixture. The antireflective properties were retained after HMDS-treatment and the transmission maximum values were above 99%. The introduction of HMDS into silica sols had also increased the LIDT of coatings from 24.3 J·cm^-2 to 37 J·cm^-2 when the molar ratio of HMDS to TEOS was 0.05:1. After some of the hydroxyl groups on the surface of the SiO₂ particle were replaced by methyl groups, from which the SiO₂ particle gained a water-repellent surface, the stability of coatings in vacuum were increased. The peak transmittance of modified sample decreased only 0.25% after conserved in vacuum circumstance for 168 hours, in contrast to 2% reduction for the unmodified sample. At the same time, the LIDT of modified coating retained a high LIDT of 30.8 J·cm^-2.