雷射干涉重力波偵測組織LIGO(Laser Interferometer of Gravitational-wave Observatory)利用大型麥克森干涉儀量測重力波訊號。因為重力波訊號非常微弱，容易受背景雜訊影響，所以降低背景雜訊可以有效提升重力波偵測器的靈敏度，探測更為微弱的重力波訊號。根據理論雜訊頻譜圖得知，在頻率約100赫茲附近總體雜訊最低，此頻率附近主要影響的雜訊為源自於雷射系統的Quantum noise以及由高反射鏡鍍膜材料所貢獻的Coating Brownian noise。本實驗室致力於降低Coating Brownian noise。根據統計熱力學的fluctuation dissipation理論，薄膜的Coating Brownian noise與薄膜的機械損耗成正比，我們藉由量測薄膜的機械損耗評估薄膜的Coating Brownian noise。此外，高反射鏡鍍膜材料需要極佳的光學性質，以減少因為吸收造成的額外熱雜訊，所以降低薄膜之光學吸收也非常重要。
在之前的研究中，低氮-氮化矽薄膜已經有很低的光學吸收及機械損耗。本論文試著利用退火製程繼續降低此材料的光學吸收及機械損耗，並研究不同的退火溫度對薄膜光學及機械性質的影響，如成分比例、結晶、折射率、膜厚、楊氏係數、應力及鍵結含量等。
研究結果顯示：低氮-氮化矽薄膜經過退火350度30分鐘後消光係數從1.51×〖10〗^(-5)下降至1.02×〖10〗^(-5)，但隨退火溫度繼續上升消光係數反而增加；而室溫機械損耗則隨著退火溫度上升而減少，在退火450度30分鐘後室溫機械損耗從7.49×〖10〗^(-5)下降至3.24×〖10〗^(-5)。此外，我們發現低氮-氮化矽薄膜的光學吸收會隨著Si-H鍵含量減少而上升；而室溫機械損耗則會隨著Si-H鍵含量減少而下降。

The group of Laser Interferometer of Gravitational-wave Observatory (LIGO) built large Michelson interferometers to detect gravitational wave directly. The sensitivity of these detectors around 100 Hz are limited by the quantum noise and coating Brownian noise, which are contributed from the laser system and the coating materials of high reflective mirror, respectively. Our laboratory focused on reducing the coating Brownian noise. According to the fluctuation-dissipation theorem, there is a positive correlation between the coating Brownian noise and the mechanical loss of films. So we measured the mechanical loss of films to calculate the related coating Brownian noise. In addition, it is also important to reduce the optical absorption of the films.
It has been discovered in the previous study that the silicon-rich silicon nitride film has the low optical absorption and mechanical loss. In our research, we tried to further reduce optical absorption and mechanical loss by using the annealing process. In addition, we investigated the effects of optical and mechanical properties of thin films in different annealing temperatures such as N/Si ratio, structure, refractive index, physical thickness, Young's modulus, stress, and bond concentration.
We found that the optical absorption of silicon-rich silicon nitride films decreases from 1.51×〖10〗^(-5) to 1.02×〖10〗^(-5) in 350℃ annealed for 30 minutes, but while the temperature keeps on rising, the optical absorption increases. The result also shows that the higher annealing temperature gets, the lower room-temperature mechanical loss reaches; the room-temperature mechanical loss drops from 7.49×〖10〗^(-5) to 3.24×〖10〗^(-5) in 450℃ annealed in 30 minutes. In conclusion, we observed that there is a negative correlation between the optical absorption and the number of Si-H bonds; in contrast, the relationship between the room-temperature mechanical loss of silicon-rich silicon nitride films and the number of Si-H bonds is a positive correlation.

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