Hydride Vapor Phase Epitaxy of Freestanding GaN Films

본 논문에서는 III-V족 화합물 반도체인 GaN 물질을 ZnO를 template 층을 이용하여 Sapphire 기판 위에 성장하였고 구조적, 광학적 조사를 통하여 고품질의 Freestanding(FS)-GaN 기판의 제작에 대한 가능성을 고찰하였다. 이 논문의 목적은 종래에 사용해 오던 기판 제거 방법의 문제점들에 의해 고품질의 성장이 제한이 되어온 것에 대하여 GaN 기판을 ZnO를 sacrificial 층으로 사용, 성장 조건의 최적화에 따른 FS-GaN 기판의 새로운 성장 가능성을 보여줌에 있다. 본 논문은 총 6 장으로 구성되어 있으며 각 장의 내용은 다음과 같다. 제 1장에서는 기본적인 GaN 물성과 종래의 FS-GaN 기판제작이 가지고 있는 문제점, 그리고 다양한 응용분야에 대하여 설명을 하였다. 제 2장에서는 제작된 자립형 GaN 기판을 성장, 평가하기 위해 본 연구에서 사용한 방법인 HVPE, SEM, HRXRD 그리고 PL 측정에 대하여 정리를 하였다. 제 3장은 GaN의 성장을 위한 ZnO template 층의 적합한 polarity의 확인에 있다. 다른 polarity를 가지는 ZnO 위에 성장된 GaN의 구조적 및 광학적 특성에 대해 고찰 하였다. 제 4장에서는 성장온도 및 가스 flow (V/III)의 변화를 통하여 GaN 성장에 적합한 성장조건을 구조적 및 광학적 특성 평가를 통하여 확인하였다. 그리고 제 5장에서 3장과 4장에서 확인 된 ZnO의 polarity와 GaN의 성장조건을 통하여 자립형 GaN 기판을 화학적 etching 방법을 통하여 제작 하였으며 마지막으로 제 6장에서는 본 논문에서 얻은 결과를 정리하여 결론 및 향후 과제에 대해 기술하였다.In this thesis, the growth structural and optical properties of FS-GaN with ZnO template buffer layer have been investigated. The objective of this thesis is to fabricate the high quality FS-GaN substrate by using ZnO sacrificial layer. In the chapter 1, the fundamental GaN properties, problems in the fabrication of FS-GaN substrate, and many application of the GaN are introduced. In the chapter 2, the principles of hydride vapor phase Epitaxy (HVPE), scanning electron microscopy (SEM), high resolution X-ray diffraction (HR-XRD), and photoluminescence (PL) are explained. In the chapter 3, ZnO polarity was determined for the growth of GaN on ZnO. In the chapter 4, the high quality GaN film growth was achieved by using ZnO sacrificial layer and optimization of growth condition. And in the chapter 5, a new self-separation method by using chemical etching of ZnO template was developed. And the quality of GaN was characterized in terms of structural and luminescence properties. Finally, the results found from this thesis are summarized and concluded in the chapter 6.논 문 요 약 1 Abstract 3 Figure list 4 Table list 8 Chapter 1. Introduction 1.1) Introduction to III-Nitrides semiconductors 1.1.1) Application of GaN 9 1.1.2) Physical properties of GaN 12 1.1.3) Problems in GaN epitaxy 13 1.1.4) Piezoelectric polarization in GaN 17 1.2) Necessity of Free-standing GaN substrate 1.2.1) History of GaN substrates and problems in fabrication 19 1.2.2) Difficulty in substrate removal techniques by HVPE 22 1.3) Proposal and purpose of this study 28 Reference 31 Chapter 2. Experimental 2.1) growth method 2.1.1) Hydride Vapor Phase Epitaxy 35 2.2) Characterization of measurement method 2.2.1) Scanning Electron Microscopy (SEM) 37 2.2.2) High Resolution X-ray Diffraction (HRXRD) 2.2.2.1) Conventional high resolution X-ray 40 2.2.2.2) &#61559scan 42 2.2.3) Photoluminescence (PL) 45 References 50 Chapter 3. Comparison of GaN on Zn-polar/O-polar ZnO 3.1) Introduction 51 3.2) Experimental details 53 3.3) ZnO etching rate of GaN after growth 53 3.4) Surface morphology and Photoluminescence (PL) intensity 54 3.5) Conclusion 55 Reference 56 Chapter 4. Optimization of growth condition for high quality GaN grown on ZnO template 4.1) Introduction 57 4.2) Experiment details 57 4.3) Effect of the growth temperature for GaN on ZnO growth 4.31) ZnO etching rate after GaN growth 58 4.3.2) Surface morphology 59 4.3.3) Evaluation of structural property by HRXRD 60 4.3.4) Room temperature (RT) of PL spectrum 61 4.4) Effect of the V/III ratio for GaN on ZnO growth 4.4.1) ZnO etching rate after GaN growth 62 4.4.2) Surface morphology 63 4.4.3) Evaluation by HRXRD 64 4.4.4) Room temperature (RT) of PL spectrum 65 4.5) Conclusion 66 Reference 67 Chapter 5. Fabrication of Freestanding GaN substrate 5.1) Introduction 68 5.2) Experimental details 69 5.3) Fabrication sequence of the self-separated FS-GaN substrate 69 5.4) Evaluation by HRXRD 70 5.5) Low temperature Photoluminescence (PL) properties 71 5.6) Temperature dependence Photoluminescence (PL) properties 72 5.7) Conclusion 73 References 74 Chapter 6. Summary and conclusion 75 Appendix A 77 감사의 글 79 Curriculum vitae 80-2&#61553scan (rocking curve) and &#6155

A Rhetorical Analysis of Party Manifestos

학위논문(석사) -- 서울대학교대학원 : 국제대학원 국제학과(국제협력전공), 2023. 2. 김태균.ODA expenditure for any given democratic donor country is primarily determined by the incumbent political party. In line with common speculation, Thérien (2000, 2002) and Tingley (2009) argue that as a government becomes more right-leaning on the political spectrum, foreign aid effort decreases. Based on the indicated theoretical framework, this article selects the United Kingdom as a case study amongst other two-party democracies to identify distinct patterns of ODA expenditure that arise from the change in the majority party and whether the challenger party displays extra effort on foreign aid policies during the election periods of 1970, 1974, 1979 and 1997. The results from the rhetorical analysis of party manifestos indicate that in the case of the UK, only the left-leaning party leverages ODA policy as a strategic tool in challenging the incumbent party. Furthermore, ODA expenditure increases with the politically left-leaning party (Labour) and decreases when the majority party changes to the political right (Conservative).경제협력개발기구(OECD)의 자료에 의하면 공적개발원조(ODA)는 원조국들의 경제상황 변동에 큰 탄력성을 보이는 유일한 형태의 대외원조다. 일반적인 경우, 원조국의 ODA 지출 관련 결정은 각 국가의 여당 또는 우세 정당에 의해 이행된다. Thérien (2000;2002)과 Tingley (2009)는 일개 정부의 정치적 스펙트럼이 우경화(보수화)됨에 따라 해외 원조 지출이 감소한다고 주장한다. 본 논문은 이 주장을 바탕으로 영국의 사례연구를 통해: 첫째, 우세 정당의 교체가 ODA 지출 수준에 미치는 영향 분석과; 둘째, 선거 시점에서의 야당의 ODA 정책 활용성을 분석한다.Abstract 2 1. Introduction 6 1.1 Purpose and Question of Research 6 1.2 Background of Research 7 1.3 Research Framework and Methodology 11 1.4 Limitations 16 2. Literature Review 17 3. Overview of ODA Development in the UK 21 3.1 Early Days of UK Foreign Aid: 1920s-1960s 21 3.2. UK ODA Development: 1960s-2000s 23 3.3. UK ODA Development: 2000s to Today 29 4. Political Parties and ODA Efforts 37 4.1 Labour to Conservative in 1970 and 1979 39 4.2 Conservative to Labour in 1974 and 1997 46 5. Findings and Discussion 55 6. Conclusion 60 Bibliography 62석

Serum Dickkopf-1 in Combined with CA 19-9 as a Biomarker of Intrahepatic Cholangiocarcinoma

Dickkopf-related protein 1 (DKK-1) has a diagnostic and prognostic value in various malignant tumors. We investigated the diagnostic and prognostic performance of DKK-1 in combination with carbohydrate antigen 19-9 (CA 19-9) in cholangiocarcinoma (CCC) patients. Serum DKK-1 levels were measured using enzyme-linked immunosorbent assay. The receiver operating characteristic (ROC) curve, area under ROC (AUROC) analyses, Kaplan-Meier method, and Cox proportional hazard model were used to evaluate the diagnostic and prognostic performance of DKK-1 in combination with CA 19-9. We checked DKK-1 levels in 356 CCC patients and found that DKK-1 was significantly elevated only in 79 intrahepatic CCC (ICC) patients compared to controls (340.5 vs. 249.8 pg/mL, p = 0.002). The optimal cutoff level of DKK-1 used to identify ICC patients was 258.0 pg/mL (AUROC = 0.637, sensitivity = 59.5%, specificity = 56.9%, positive predictive value (PPV) = 40.5%, negative predictive value (NPV) = 74.0%, positive likelihood ratio (LR) = 1.38, and negative LR = 0.71). Using this cutoff, 47 (59.5%) patients were correctly diagnosed with ICC. DKK-1 in combination with CA 19-9 showed a better diagnostic performance (AUROC = 0.793, sensitivity = 74.7%, specificity = 56.3%, PPV = 45.7, NPV = 81.8, positive LR = 1.71, and negative LR = 0.45) than CA 19-9 alone. The low DKK-1 and CA 19-9 expression group had a significantly longer overall survival (OS) than the high expression group (p = 0.006). The higher level of DKK-1 and CA 19-9 was independently associated with shorter OS (hazard ratio = 3.077, 95% confidence interval 1.389-6.819, p = 0.006). The diagnostic and prognostic performance of DKK-1 in combination with CA 19-9 might be better than those of CA 19-9 alone in ICC patients.ope

(An)Analysis of implementation process of New Korean Community-oriented Policing System : mainly focused behavior of street-level police bureaucracy

학위논문(석사)--서울대학교 행정대학원 :행정학과 정책학전공,2005.Maste

(The)Effect of running and muscular resistance training in Circadian Rhythms on Melatonin, Growth hormone, VO₂max, muscular strength, muscular endurance, flexibility, fat mass, and lean body mass

학위논문(석사)--서울대학교 대학원 :체육교육과,2005.Maste

운동이 염증 반응과 항산화 방어기전에 미치는 영향

Thesis(doctors) --서울대학교 대학원 :체육교육과,2008.Docto