可視化水平區熔法生長等計量比鈮酸鋰單晶之研究

Abstract

工業上，生長高品質非線性光學鈮酸鋰單晶製程中，一般採用柴式法生長，但由於存在著生長偏析的影響，造成晶體在軸向(生長方向)的摻雜濃度分佈不均勻，使用區熔法藉由連續固體進料的方式可以解決濃度分佈不均的問題。而大部分生長氧化物晶體的方法中，都存在著直徑控制的問題，因此，在本論文中，我們使用水平區熔法來生長等化學計量比鈮酸鋰單晶(SLN)，以白金片作為承載材料工具，晶體尺寸直接由白金船大小決定，沒有沿生長方向晶體尺寸控制不均的問題。 在研究的過程中，我們已建立一套可視化水平區熔系統，藉著可視化系統，我們可觀察熔區界面、接種情形，並利用不同的加熱器形狀設計控制出凸到平的生長界面。另一方面，我們長出較大晶粒的SLN晶體，除此之外，在晶體組成量測方面，在晶體各部位的鈮鋰比都相當均勻(0.97 0.001)。

In industry, lithium niobate(LN) high quality nonlinear optical single crystal is usually grown by Czochralski method, but due to the segregation problem, the dopant distribution in growth direction is not uniform. It can be solved by using the Zone-Leveling method with continuous sold feeding. Besides, most methodologies growing the oxide crystals have difficulties in diameter control. In present research, we decide to grow the stoichiometric lithium niobate (SLN) crystals with Zone-Leveling method. We use the platinum shell to be a boat loading the material, and the crystal size can be decided by the pt-boat directly. As a results the problem of the non-uniform size of crystals in growth direction would not appear in present Zone-Leveling mehod. In present thesis, we have built a Visual Horizontal Zone-Leveling system. By the visual system, we can observe the melting interface, seeding condition and control the growth melt/solid interface to become convex or flat by different heater shape designs. In the other hand, we have grown larger grain SLN crystal. Besides, the measurements of crystal compositions in all parts, it exists good uniformity for Li/Nb ratio (0.97 0.001).