雷射干涉重力波天文台(Laser Interferometer Gravitational-Wave Observatory, LIGO)透過大型麥克森干涉儀來觀測重力波。因為重力波訊號非常微弱，故其致力於提升量測上的靈敏度及降低材料本身產生的薄膜熱擾動雜訊(Coating Brownian noise)，此雜訊是藉由量測與其成正比之薄膜機械損耗來判斷。而大型麥克森干涉儀中，做為高反射鏡的薄膜材料也必須嚴格掌控其光學特性。故本實驗室著重於兩個方面研究，分別為機械特性及光學特性，研究開發低機械損耗與低光學吸收之薄膜材料。

先前本實驗室曾經使用IBS系統鍍製氮化矽薄膜，著重探討薄膜金屬汙染物的問題，也有透過降低冷卻系統水溫進行製程並找到其與金屬汙染物的關係，在冷卻系統水溫10℃時有較低的光學吸收。本論文首先對未加熱的氮化矽薄膜做一個總結，利用冷卻系統水溫10℃並改變Beam voltage600-900V進行製程，並為往後基板加熱實驗訂下最佳離子源參數設定。

除了金屬汙染物外，本實驗室也研究發現另外兩項會影響光學吸收的因子，分別是N-H鍵與矽懸鍵。而筆者查閱多篇文獻及相關資料，發現透過基板加熱系統，可以有效降低薄膜內氫元素的含量，也就是降低N-H鍵，於是筆者決定加裝基板加熱系統。而首先筆者嘗試改變基板溫度與預熱時間，兩者皆有達到降低氫含量的目的，光學吸收也有些微下降，但是一樣在10-4數量級，而薄膜內大量的矽懸鍵是造成光學吸降不下去的主因，於是筆者接著從矽懸鍵著手，透過降低Beam current進而降低鍍率，使鍵結更完整，矽懸鍵也下降了將近兩倍，光學吸收也順利進到10-5數量級。然而矽懸鍵雖有下降，但是一樣在10-19數量級，屬於相當多的含量，故未來期望透過補氫退火減少矽懸鍵，進而降低光學吸收。

Laser Interferometer Gravitational-Wave Observatory (LIGO) observes gravity waves through a large-scale Michelson interferometer. Since the signal from gravity wave is too weak to detect, LIGO is dedicated to improving the sensitivity of measurement and reducing the Coating Brownian noise of the film, which is determined by measuring the mechanical loss of the film, that is proportional to the noise. Besides, in the large-scale Michelson interferometer, the optical properties of the thin film material used as a high-reflection mirror must also be strictly controlled. Therefore, our laboratory focuses on the research of two aspects, one is about mechanical properties; the other is about optical properties, and is committed to devoted to researching and developing thin film materials with low mechanical loss and optical absorption.

Previously, we used to deposit silicon films nitride by IBS. We researched the pollution with stainless metal in the film, and also finding the relationship between it and water temperature by doing the process about reducing water temperature of the cooling system, there are lowest optical absorption when the water temperature is 10℃. This thesis first summarizes the unheated silicon nitride film, the water temperature of the cooling system is 10℃ and the beam voltage is changed from 600V to 900V for the process, and also setting the best parameter for the substrate heating experiments later.

In addition to metal contaminants, IBS group also found two other factor that affect optical absorption, it’s nitrogen-hydrogen bond and silicon dangling bond. In order to improve optical absorption, I researched many papers and documents. As a result, I found that through the substrate heating system can reduce the concentration of hydrogen in the films, it means that nitrogen-hydrogen bond can be reduced, thus, we decided to use substrate heating system with experiment. First, I tried to change the substrate temperature and preheating time, both of them have achieved the goal of reducing the hydrogen content, and the optical absorption was also slightly reduced, but it is still of the order of 10-4. The numerous silicon dangling bonds in the films is the reason why optical absorption can not be reduced. Therefore, I started with silicon dangling bond by reducing the beam current and then reducing the deposition rate, to make the bond more complete. As expected, the bond was reduced about two times, and the absorption also advanced to the order of 10-5. However, although the concentration of silicon dangling bond was decreased, it is still of the order of 10-19 cm-3, which is a considerable number. In the future, it is expected that silicon dangling bond will be reduced through hydrogen annealing, thereby decreasing optical absorption.

[1] Einstein, Albert. "Besprechung von" A. Einstein: Die Grundlage der allgemeinen Relativitätstheorie"." Naturwissenschaften 4 (1916): 481.
[2] Scientific, L. I. G. O., Virgo Collaboration, and B. P. Abbott. "Erratum: Tests of General Relativity with GW150914 [Phys. Rev. Lett. 116, 221101 (2016)]." Physical review letters 121.12 (2018): 129902.
[3] Bassan, Massimo. "Advanced interferometers and the search for gravitational waves." Astrophysics and Space Science Library 404 (2014): 275-290.
[4] Collaboration, LIGO Scientific. "Instrument Science White Paper 2018." (2018).
[5] Callen, Herbert B., and Theodore A. Welton. "Irreversibility and generalized noise." Physical Review 83.1 (1951): 34.
[6] Greene, Richard F., and Herbert B. Callen. "On the formalism of thermodynamic fluctuation theory." Physical Review 83.6 (1951): 1231.
[7] Callen, Herbert B., and Richard F. Greene. "On a theorem of irreversible thermodynamics." Physical Review 86.5 (1952): 702.
[8] 黃榛莉, “電漿輔助化學氣相沉積之氮化矽薄膜其熱退火後光學特性與無氨氣電漿輔助化學氣相沉積法之氮化矽薄膜其光學及機械特性之探討” , 國立清華大學碩士論文 (2019)
[9] Kitabatake, Makoto, and Kiyotaka Wasa. "Hydrogen‐free SiN films deposited by ion beam sputtering." Applied physics letters 49.15 (1986): 927-929.
[10] 陳俊廷, “以離子束濺鍍法鍍製氮氧化矽薄膜探討其光學特性” , 國立清大學碩士論文 (2020)
[11] Fremerey, Johan K. "Residual gas: traditional understanding and new experimental results." Vacuum 53.1-2 (1999): 197-201.

[12] Schneider, Jochen M., et al. "On the effect of hydrogen incorporation in strontium titanate layers grown by high vacuum magnetron sputtering." Applied physics letters 75.22 (1999): 3476-3478.
[13] 劉冠廷, “以離子束濺鍍法鍍製氮化矽薄膜其光學特性之探討” , 國立清大學碩士論文 (2020)
[14] 黃文正, “以離子束濺鍍法製作低損耗薄膜應用於雷射干涉重力波偵測儀之高反射鏡製程準備”, 國立清華大學碩士論文 (2012)
[15] 黃柏豪, “以離子束濺鍍法鍍製奈米多層薄膜其光學特性之退火校應與離子束濺鍍法鍍製氮化矽薄膜之材料特性分析” , 國立清華大學碩士論文 (2019) [16] 張臨安, “以電漿輔助化學氣相沉積法鍍製高氮氮化矽薄膜其熱退火對光學特性與機械特性之影響”, 國立清華大學碩士論文 (2018)
[17] 康乃中, “光熱共光路干涉儀系統之設置與電漿輔助化學氣象沉積法沉積之氮化矽薄膜光學吸收研究”, 國立清華大學碩士論文 (2013)
[18] Roth, Alexander. Vacuum technology. Elsevier, 2012
[19] 蔡東霖, “以低壓化學氣相沉積法鍍製之氮化矽薄膜在雷射重力波偵測器反射鏡應用之研究”, 國立清華大學碩士論文 (2021)
[20] Chiang, Donyau, et al. "Determination of the Refractive Index of Molybdenum Using a Spectrophotometric Method." Sensors and Materials 31.11 (2019): 3517-3526.
[21] Sian, Tarsame S., and G. B. Reddy. "Optical, structural and photoelectron spectroscopic studies on amorphous and crystalline molybdenum oxide thin films." Solar energy materials and solar cells 82.3 (2004): 375-386.
[22] Yamada, Itsunari, et al. "Near-infrared polarizer with tungsten silicide wire grids." Japanese Journal of Applied Physics 50.1R (2011): 012502.

[23] Hutchins, M. G., et al. "Preparation and properties of electrochemically deposited tungsten oxide films." physica status solidi (a) 176.2 (1999): 991-1002.
[24] 桂芳成, “利用電漿輔助化學氣相沉積法鍍製氮化矽與氮氧化矽薄膜建構光學吸收經驗公式”, 國立清華大學碩士論文 (2021)
[25] 高煜勛, “降低以電漿輔助化學氣相沉積法鍍製之氮氧化矽薄膜光學吸收之研究”, 國立清華大學碩士論文 (2021)