- 學位論文
近等化學計量比鉭酸鋰晶體極化之研究
The Research of Near-Stoichiometric Lithium Tantalate Crystal Poling
摘要
鉭酸鋰晶體是相當優秀之鐵電材料，應用範圍寬廣包括表面聲波、光電及波導光學技術等等，但晶體生長後未經過極化處理，材料結構上會出現若干個鐵電疇(ferroelectric domain)，在應用上將面臨有許多困難，如電疇壁的存在將造成光學量測值減弱或偏移之現象、生長的晶體材料無法出表現焦電與壓電特性。透過極化方法改變晶體的自發極化方向，從原本的多電疇( multi-domain)結構轉變為均勻的單電疇(single domain)結構，以改善晶體生長後的結構缺陷並提升晶體在應用上的價值。本論文使用實驗室所生長的ZLCz提拉法鉭酸鋰晶體作為晶體極化之材料來源，探討不同晶錠極化方法與條件對極化成果的影響，並比較不同極化方法的優缺點，再由極化過的單電疇SLT晶錠分別觀察其x、y、z軸切面與不同z軸偏離角度之切面的蝕刻變化。 在論文的附錄中，我們也對近等化學計量比鎂摻鉭酸鋰晶片做氣相傳輸平衡(VTE)處理，由物性量測結果探討VTE處理的成效。
關鍵字
鉭酸鋰,鐵電晶體,極化,電疇並列摘要
Lithium Tantalate single crystal is a potential electro-optical material which can be used in many ways, such as surface acoustic wave (SAW), non-linear optics and optical waveguide etc., but SLT single crystals without poling treatment will have many problems in its application. For examples, one is the domain walls in SLT wafers will make the measurement signal weaken or shift, and the other is SLT single crystals cannot perform its pyroelectricity and piezoelectricity. If we use external electric field to electrify the SLT ingot at high temperature, the ferroelectric domains in SLT ingots will change to single domain structure with identical polarized direction. So that poling treatment can improve the structure in SLT single crystals and upgrade its application merit. Here, we used the SLT crystals grown by ZLCz method in our laboratory for research of poling treatment, and discuss the effects in different paved material between electrodes and SLT z-cut surfaces and in different poling conditions. Furthermore, we also compared and characterize the poling methods, and observed the etching surfaces in x, y, z axes and different angle from z axis on SLT ingot. In appendix, we also performed VTE treatment for our MgO doped near-stoichiometric lithium tantalate wafers and characterized the VTE results by physical measurement data.