以RF濺鍍法沉積鈮酸鋰薄膜之研究

The Study of Lithium Niobate Thin Films by RF Sputtering Method

黃富財(Fu-Tsai Hwang)

指導教授 ： 李清庭 ； 張正陽

國立中央大學/理學院/光電科學研究所/博士(2006年)

摘要

摘要
很高品質的鈮酸鋰薄膜以高頻磁控濺鍍法被沉積在矽及石英基板上可作為聲表面波及光波導的應用。我們探討過表面形態、紋理、結晶性、膜厚、折射率、消光係數等特性和濺鍍參數及退火過程之依存關係。我們由熱差分析儀測量最佳的濺鍍溫度。利用x光及低撂角x光繞射儀測試薄膜的結晶性。利用原子力顯微鏡測試薄膜表面的粗糙度。借助於原子力顯微鏡和x光繞射量測，以探討鈮酸鋰表面形態和結晶特性變化之機制。透過本研究發現最佳的濺鍍溫度約為575℃，最佳的氣體流量比Ar/O2 為1：1。同時發現較合適的RF濺鍍功率為100W。由橢圓儀量測鈮酸鋰薄膜之膜厚、折射率、消光係數，發現薄膜之折射率為2.2(波長為632.8奈米)它與發表的折射率值符合。同時我們量測到薄膜之消光係數約為零，這代表本研究沉積的薄膜適合作為光波導。

關鍵字

鈮酸鋰薄膜

並列摘要

Abstract
Very high quality LiNbO3 films were deposited on both silicon and quartz substrates for the applications of surface acoustic wave and optical waveguide by RF magnetron sputtering. We have investigated the dependence of the surface morphology, texture, crystallinity, thickness, refractive index, extinction coefficient properties with the sputtering parameters and annealing process. The optimum deposition temperature was measured by differential thermal analysis. The crystallinity was examined by x-ray and low angle x-ray diffractometer (XRD). The roughness of LiNbO3 thin films was examined by atomic force microscopy (AFM). AFM and XRD measurements were used to investigate the mechanisms of the variation in the surface morphology and crystallinity of LiNbO3 thin films.The optimum deposition temperature was found to be about 575℃. In this investigation the optimum ratio of the mass flow Ar/O2 was found to be about 1:1. Simultaneously, the RF power necessary for texture was found to be about 100W. The thickness, refractive index and extinction coefficient of LiNbO3 thin films were examined by ellipsometer. We have found the refractive index (n) is 2.2 (at 632.8nm), which is identical with the parameter of LiNbO3 ever reported. At the same time, the extinction coefficient of LiNbO3 thin films approachs to zero , represents that these thin films are suitable for optical waveguides.

並列關鍵字

Lithium Niobate Thin Films

參考文獻

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“Physical structure of lithium niobate thin films,” IEEE Trans. Ultrason.,

Ferroeled., Freq. Contr., vol. 38 pp.640-843,1991.