本論文研究不同摻雜濃度(xNb)與不同氧分壓下成長之鈮摻雜鈦酸鍶(Nb:SrTiO3)薄膜，發現氧空缺是主導九個數量級以上導電率變化的關鍵因素，而不是鈮的摻雜濃度。一般而言摻雜五族的鈮被認為會取代四族的鈦，因此貢獻一自由電子。但點缺陷如氧空缺與鈮的反晶格位會同時伴隨產生，因此會產生多重價態的鈮。在薄膜成長過程中些微的氧氣供應都會在NbTi晶格位附近產生Oi與Nbi，這些缺陷會捕捉自由載子進而降低了導電性。電子傳導機制經由能帶間躍遷與變程跳躍導電機制並聯描述，而這是鈮、鍶、與鈦原子之間交互的氧化還原反應集體造成的。

The emergence of wide range electrical conductivity (more than 9 orders in magnitude) in SrTiO3 (STO) thin films containing various levels (xNb) of Nb dopants (Nb:STO) due to critical dependence on PO2, rather than xNb, is interpreted as a result of oxometallates formation through route of redox reactions. The dopants are supposed to substitute for Ti to give one free electron, assuming Nb+5 oxidation states, but other point defects, such as oxygen vacancies and Nb antisites, also arise in company, resulting in emergence of various multivalent oxides of Nb. Any presence of oxygen during growth leads to O_i and Nb_i nearby Nb_Ti sites, capturing potential free carriers from Nb3d hindering the electronic conduction. Electrical transport behaviors are described with parallel mechanisms of band conduction and variable-range hopping conduction, responsible by the collective redox reaction of the Nb, Sr and Ti atoms.

審定書 i
致謝 ii
中文摘要 iii
Abstract iv
目錄 v
圖次 viii
表次 xii
Chapter 1. Introduction 1
Introduction SrTiO3 1
TCO applications via double doping of SrTiO3 3
Interstitial sites and ineffective doping 5
Motivation 7
Chapter 2. Experimental setup 10
2.1 Introduction 10
2.2 Sample growth procedure 10
2.2.1 Sputtering 10
2.2.2 Sample growth procedure 12
2.2.3 Thickness characterization 14
2.2.4 Sample appearance 15
2.3 X-ray diffraction (XRD) 16
2.3.1 Structural analysis by XRD 17
2.4 Chemical quantification 19
2.4.1 xNb of SrTi1-xNbxO3 by calculation of sputtering rate 21
2.5 Transmission electron microscopy and specimens preparation 22
2.6 X-ray photoelectron spectroscopy 23
2.6.1 Detail procedures for XPS valence state analysis 24
2.7 Kröger-Vink notation 25
2.8 Electrical measurement 26
2.8.1 E-beam evaporation 26
2.8.2 Rapid thermal annealing (RTA) 28
2.8.3 I-V measurement 29
2.8.4 Contact resistance measurement 30
2.9 Dielectric measurement 31
Chapter 3. Physical properties 33
3.1 Structural analysis by XRD 33
3.1.1 Omega-2theta scan 33
3.1.2 ϕ(phi)-scans 39
3.1.3 Grazing-incidence XRD (GIXRD) 41
3.1.4 Discussion on XRD structural analysis 42
3.2 Transmission electron microscopy (TEM) 45
3.2.1 Bright field (BF) for C series 47
3.2.2 Diffraction pattern for C series 49
3.2.3 Discussion on the intensity of diffraction spot of (100) and (200) 50
3.3 XPS valence state analysis 61
3.3.2 Fitting for Nb 3d 64
3.3.3 Fitting for Ti 2p 66
3.4 Electrical analysis 71
3.4.1 Resistivity for as-grown samples 71
3.4.2 Resistivity versus temperature (RT) 73
3.4.3 Discussion on the carrier conduction mechanism 82
Chapter 4. Conclusion 85
References 87
Appendix 99
A1 TLM with different annealing temperature 99
A2 XPS valence state for Nb and Ti 103
A3 Valence band 103
A4 Capacity versus frequency (CF) 105
A5 Justification on the formation of Nb metallic clusters 106
A6 Optical transmission 108
A7 Additional TEM results 109

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