鈦酸鍶基板上氧化鈦薄膜自我排列機制的研究

Abstract

本論文旨在探討氧化鈦薄膜在鈦酸鍶(100)基板上自我排列的機制。在本實驗中，我們以直流濺鍍法於鈦酸鍶(100)基板上成長不同顯微結構的氧化鈦薄膜，並將其作不同溫度的退火處理。我們發現，當退火的溫度在1000℃以下時，薄膜晶粒的尺寸將隨退火溫度的升高而逐漸變大。然而當退火的溫度在1000℃以上時，薄膜皆會呈現出金紅石結構且薄膜的晶粒將會形成棒狀。而這些棒狀的晶粒可能會在鈦酸鍶(100)基板上作有規則的自我排列，但也可能呈現較不規則的排列。這些差異可以從應變能的觀點，也就是從薄膜晶粒和基板其晶格失配度的關係來說明。同時，我們也對在鈦酸鍶(100)基板上成長氧化鈦薄膜時所用的直流濺鍍條件，提供了適當的建議，以便較可能使得氧化鈦薄膜能在鈦酸鍶(100)基板上作有規則的自我排列。最後，我們對於利用脈衝雷射蒸鍍法在含有棒狀的氧化鈦薄膜晶粒所形成之圖案的鈦酸鍶(100)基板上選擇性磊晶成長釔鋇銅氧高溫超導薄膜所作的嘗試，也獲得了不錯的結果。

This thesis mainly discusses the mechanism of self-assembled TiO2 thin film on SrTiO3(100)(STO(100)) substrate. TiO2 films with various micro- and crystalline structures were deposited on STO(100) substrate by dc sputtering. The films were then annealed at various temperatures. We found that the grain size increased with increasing annealing temperature when the annealing temperature was below 1000oC. However, all films transformed to rutile structure with distinct rod-shaped grains when the annealing temperature was above 1000oC. These rod-shaped grains may be self-assembled into regular arrangement, depending on the starting phase and microstructure of the as-deposited films. The results were interpreted from the viewpoint of the strain energy originated from the lattice mismatch between the thin film and the substrate. Favorable conditions for obtaining self-assembled TiO2 on STO(100) substrates were suggested, as well. Finally, we tried to use the self-assembled template for “selective epitaxial growth (SEG)” of YBa2Cu3O7(YBCO) high-Tc superconducting thin films. The resulting films followed the patterns formed by TiO2 grains, showing excellent selectivity of TiO2 for growing YBCO films.