TiO2膜消光系数的确定及制备参量的影响

基于窄带干涉滤光片的峰值透射率测量可以直接反演出薄膜的消光系数,从而得到了一种简易而又精确的评价薄膜微弱损耗的新方法。阐述了确定弱吸收薄膜消光系数的基本原理,并分析了这种评价方法的基本精度。讨论了离子束溅射TiO2薄膜的制备参量对薄膜消光系数的影响。发现溅射速率和氧分压是影响TiO2薄膜损耗的灵敏因素。在保持其它参量不变的条件下,溅射速率从0.35nm/s下降到0.23nm/s,TiO2薄膜的消光系数从3.9×10-5下降到2.1×10-5;辅助离子源的Ar∶O比从1∶2变化为1∶4,对应的消光系数从5.6×10-5下降到2.3×10-5。此外,随着基板温度的提高,损耗也会有所增加。TiO2薄膜消光系数评价的合理性表明由窄带滤光片的峰值透射率来反演薄膜的消光系数是可行的。

Determination of the Extinction Coefficient of TiO2 and Effect of Preparation Parameters

Based on measurement of peak transmittance of narrow band filter, the extinction coefficient of a weakly absorbing thin film can directly be calculated. This is a new method used for determination of the extinction coefficients of weakly absorbing thin films with ease to do and very high precision. The principle of measurement is illustrated and the precision of this method is analyzed. The effect of preparation parameters on the extinction coefficients of TiO_2 films deposited by ion-beam-sputtering is discussed. The experiment shows that the deposition rate and ratio of ArO_2 during the deposition are important factors. When the rate reduces from 0.35 nm/s to 0.23 nm/s, the extinction coefficient of TiO_2 film falls from 3.910~(-5) to 2.110~(-5); and when the ratio of ArO changes from 12 to 14, the extinction coefficient of TiO_2 film falls from 5.610~(-5) to 2.310~(-5). In addition, the optical loss increases with substrate temperature rising. It is proved that the determination of the extinction coefficient of weakly absorbing thin films, by means of measured peak transmittance of narrow band filter, is a successful method.