臺灣博碩士論文加值系統

在許多早期的研究中發現，鈦酸鋇(BaTiO3)薄膜之電性質與其顯微結構、摻雜物元素和退火溫度有關。本研究是利用射頻磁控濺鍍鈦酸鋇(BaTiO3)薄膜，藉由添加0.11at%, 0.28at% 和1.1at% 的鈧(Sc) ?雜元素來改變鈦酸鋇薄膜的特性。未經過退火處理的薄膜是非晶質狀態，經過不同溫度的退火處理之後(約550°C以上)，發現結晶的現象。隨著退火溫度的提升，結晶的狀態更為明顯。
本研究討論不同溫度的退火處理和薄膜中的Sc含量對於酸鋇薄膜性質影響。在介電性質方面，鈦酸鋇薄膜的介電常數會隨退火溫度增加而增加，最主要的原因是晶粒的成長和結晶相的生成，0.11at%Sc-BTO試片經過650°C退火後具有最大介電常數約為347。然而鈦酸鋇薄膜的介電常數隨著Sc的摻雜小幅的下降。但Sc的摻雜有效降低漏電流密度。1.1at% Sc的鈦酸鋇薄膜經過650°C退火後具有最低的漏電流密度5.6×10-8 A/cm2。在未退火的情況下，0.11at%和0.28at%Sc-BTO遠比純的酸鋇薄膜具有較低的漏電流密度8.7×10-12 A/cm2。

In many previous investigations, microstructure and electric properties of BaTiO3 (BTO) thin films have been shown to depend on type and amount of dopant as well as post-annealing temperature. This study reports the effects of Sc dopant on BT thin films fabricated by r.f. magnetron sputtering on Pt/Ti/SiO2/Si substrates. The BTO films were doped with 0.11at%Sc, 0.28at%Sc and 1.1at%Sc. The post-annealing was performed at 550, 600 and 650�aC. The dielectric constants of pure and Sc-doped BTO thin films are found to increase with increasing annealing temperature, while they decrease with increasing Sc content. The Sc dopant is effective to reduce leakage current as well as dielectric loss compared to the pure BTO film. The lowest leakage current was obtained for the 1.1%Sc-doped BTO thin film. This low leakage current may be attributed to the substitution of Sc in the B sites of BTO lattices, which might have behaved as an electron acceptors. Those Sc-doped films annealed at 650°C showed the high dielectric constant of approximately 347 measured at 1 MHz for 0.11%Sc-doped BTO films and low leakage current density of 5.6×10-8 A/cm2 at an electric field of 250 KV/cm for 1.1%Sc-doped BTO films. The 0.11% and 0.28%Sc-doped films without annealing showed the lower leakage current density of 8.7×10-12 A/cm2 at an electric field of 250 KV/cm.

摘要 I
Abstract II
Acknowledgements III
Contents IV
List of tables VI
List of figures VIII
Chapter 1 Introduction 1
Chapter 2 Background 3
2-1 Materials 3
2-1-1 Perovskite Structure 3
2-1-2 Barium Titanate 4
2-1-2-1 Ferroelectric Property [13] 5
2-1-2-2 Paraelectric Property [13] 6
2-1-3 Sc-doped BaTiO3 6
2-2 Preparation Method of Sc-doped BTO Thin Film 10
2-2-1 Principle of sputtering 11
2-2-2 RF Magnetron sputtering 12
2-3 Electrical Properties 14
2-3-1 Polarization mechanisms 14
2-3-2 Dielectric constant and dielectric loss 16
2-3-3 Leakage current 17

Chapter 3 Experimental procedure 35
3-1 Pre-deposition preparation 35
3-1-1 Target preparation 35
3-1-2 Substrate preparation [12] 36
3-2 Film deposition 36
3-3 Thin film preparation for various characterizations 37
3-3-1 Preparation for EPMA 37
3-3-2 Post-deposition annealing 37
3-3-3 preparation for TCC, I-V and C-V measurements 38
3-4 Characterization of films 38
3-4-1 Composition analyses [1] 38
3-4-2 Crystal structure analyses [12] 38
3-4-3 Microstructure analyses 39
3-4-4 Electrical property analyses 39
Chapter 4 Results and discussion 47
4-1 Chemical analysis by EPMA and EDS 47
4-2 Crystallography by XRD 48
4-3 Chemical analysis by XPS 49
4-4 Microstructure 50
4-5 Dielectric constants for pure and Sc-doped BTO thin films 51
4-6 Leakage current for pure and Sc-doped BTO thin films 53
4-7 Temperature coefficient of capacitance (TCC) 55
Chapter 5 Conclusions 105
References 107

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