고체상태 확산 분자도핑에 의한 폴리싸이오펜계 유기 전계효과 트랜지스터의 전기적 특성 향상 연구

학위논문(박사)--서울대학교 대학원 :자연과학대학 물리·천문학부(물리학전공),2020. 2. 이탁희.유기반도체는 다른 반도체물질과 비교하여 소재의 유연성, 대면적 및 용액 공정의 장점을 갖고 있다. 이런 장점을 기반으로 유기반도체는 유기발광다이오드, 태양전지, 센서, 메모리 그리고 트랜지스터 등의 유기전자소자에 응용되고 있다. 이런 유기전자소자의 실질적인 응용을 위해 소자의 미세화 및 고속동작 소자의 구현이 필수적이다. 그러나 금속 전극과 유기반도체 사이의 쇼트키 컨택에 의해 발생하는 높은 컨택저항은 근본적으로 소자의 성능을 제한하게 된다. 실리콘 기반의 반도체 산업에서는 전극 주변의 반도체에 선택적인 이온주입 방법이 컨택특성을 향상시키기 위해 광범위하게 적용되고 있고, 이와 비슷한 접근법이 유기반도체에서의 컨택저항 문제를 해결하기 위해 응용될 수 있다. 최근에 여러 종류의 컨택도핑 방법론이 유기전자소자의 컨택저항을 감소시키기 위한 효과적인 기술로 보고된 바 있다. 하지만 소자의 스위칭 성능을 훼손하여 소자의 안정성을 두드러지게 악화시키는 도펀트 확산 문제로 인해 컨택도핑 방법론은 지금까지 유기 전계효과 트랜지스터에서 본격적으로 연구되지 않았다. 이런 측면에서, 본 학위논문에서 우선 바텀 게이트 구조의 폴리싸이오펜계 유기 전계효과 트랜지스터에 전하주입특성 향상을 위해 고체상태 확산에 의한 도펀트 분자(F4-TCNQ)의 선택적인 컨택도핑을 구현하였다. 소자의 구현 과정에서, 실험 결과와 확산방정식에 기반한 시뮬레이션을 활용하여 도핑 후처리가 도펀트 분자의 확산에 미치는 영향에 관하여 연구하였다. 한편, 높은 유전율의 절연물질을 활용한 저전압 구동 유기트랜지스터에 분자도핑 기술을 적용하여 폴리머 도핑을 활용한 소자의 미세화와 저전력 유기소자의 가능성을 보여주었다. 한편 트랜지스터의 전극 영역에 도핑영역을 한정시키기 위한 도핑 후처리의 도입에도 불구하고 도펀트 분자의 확산 문제는 완전히 해결될 수 없었다. 이 문제에 관하여, 도펀트 분자의 확산을 억제하기 위해 도펀트-차단 분자(TCNQ)를 폴리싸이오펜계 유기 전계효과 트랜지스터의 채널 영역에 선택적으로 주입하여 컨택도핑 방법론의 안정성을 향상시켰다. 이때 사용된 도펀트-차단 분자는 전기적으로 안정적이고 트랜지스터 채널 영역에서 도펀트 분자의 확산 영역에 자리 잡을 수 있는 분자를 사용하였다. 이 기술은 도펀트 분자 확산 영역를 도펀트-차단 분자로 채움으로써 도펀트 분자의 움직임에 대하여 효과적으로 장벽을 설치하는 것이었다. 이러한 도펀트-차단 방법론은 컨택저항 문제를 해결하는 유망한 방법론으로 컨택도핑을 도입하여 유기 전계효과 트랜지스터의 가능성을 극대화 하는데 기여 할 수 있을 것이다.Organic semiconductors (OSCs) have been widely studied due to their merits such as mechanical flexibility, solution processability, and large-area fabrication. Based on these merits, organic electronic devices, including organic light-emitting diodes, solar cells, sensors, memory and field effect transistors, have been widely investigated. In these organic electronic devices, downscaling and high-speed operation are essential for practical applications. However, a high contact resistance which arises from the Schottky contact between metal electrodes and OSCs fundamentally limits the device performance. In silicon-based semiconductor devices, selective ion implantation doping technique under the electrodes is widely used to enhance charge injection properties, and similar approach can be applied in OSCs to resolve the contact resistance issue. Recently, various contact doping methods have been reported as an effective way to reduce the contact resistance in organic electronic devices. However, the contact doping has not been explored extensively in organic field effect transistors (OFETs) due to the dopant diffusion problem which significantly degrades the device stability by damaging the ON/OFF switching performance. In this thesis, firstly I demonstrated a selective contact doping of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) by solid-state diffusion in poly 2,5-bis(3-hexadecylthiophen-2-yl) thieno [3,2-b] thiophene (PBTTT) to enhance carrier injection properties in bottom-gate PBTTT OFETs. In this development, I investigated the effect of post-doping treatments on diffusion of F4-TCNQ molecules by using the experimental data and a numerical simulation based on a modified Ficks diffusion equation. Furthermore, the application of the doping technique to the low-voltage operation of PBTTT OFETs with high-k gate dielectrics demonstrated a potential for designing scalable and low-power organic devices by utilizing doping of conjugated polymers. However, in spite of introducing post-doping treatments in order to confine the doped regions at the source-drain contact regions of OFETs, the dopant diffusion problem could not be resolved completely. Regarding this issue, I improved the stability of the contact doping method by selectively incorporating tetracyanoquinodimethane (TCNQ) as dopant-blockade molecules in PBTTT film in order to suppress the diffusion of the dopant molecules. The dopant-blockade molecules were carefully chosen such that they are electrically inactive and they readily locate themselves in the diffusion paths of the dopants within the active channel of the OFETs. This technique effectively constructed barriers against the motion of dopant molecules in the potential diffusion sites by filling them with the dopant-blockade molecules. Therefore, the dopant-blockade method will maximize the potential of OFETs by employing the contact doping method as a promising route towards resolving the contact resistance problem.Chapter 1. Introduction 1 1.1. Brief introduction of organic electronics 1 1.2. Contact resistance problem in organic semiconductors 2 1.3. Contact doping via solid-state diffusion 3 1.4. Outline of this thesis 4 References 5 Chapter 2. Enhanced Charge Injection Properties of Organic Field Effect Transistor by Molecular Implantation Doping 8 2.1. Introduction 8 2.2. Experiments 11 2.2.1. Device fabrication process 11 2.2.2. Electrical characterization 15 2.2.3. Spectroscopy and microscopy 15 2.2.4. Contact resistance extraction by Y-function method 16 2.3. Results and discussions 18 2.3.1. Ultraviolet-visible absorption spectroscope 18 2.3.2. Electrical characterization of PBTTT OFETs 19 2.3.3. ON/OFF ratio stability of the doped-contact PBTTT OFETs 21 2.3.4. Numerical simulation of the diffusion of F4-TCNQ 25 2.3.5. Band diagram analysis 30 2.3.6. Low-voltage operation OFETs by using high-k dieletric 33 2.4. Conclusion 37 References 38 Chapter 3. Highly stable contact doping in organic field effect transistors by dopant-blockade method 43 3.1. Introduction 43 3.2. Experiments 47 3.2.1. Materials and device fabrication process 47 3.2.2. Device and film characterization 51 3.3. Results and discussions 52 3.3.1. Ultraviolet-visible absorption spectroscope 52 3.3.2. ToF-SIMS and XRR measurements 53 3.3.3. Electrical characterization of the DB/DC-FET 55 3.3.4. ON/OFF ratio stability of the DB/DC-FET 57 3.4. Conclusion 62 References 63 Chapter 4. Summary 67 국문초록(Abstract in Korean) 69 감사의 글 71Docto

자급자족 도시를 위한 가락시장의 도시 농장화에 관한 연구

학위논문 (석사)-- 서울대학교 대학원 : 건축학과, 2014. 2. Peter Winston Ferretto.Food plays a key role in our daily life. It has a powerful influence on regional and cultural development patterns. The urban-rural relationship is intrinsic to cultural development. The city relies on the countryside to produce food and sustain the urban infrastructure. Historically, rural and agricultural areas, have played a major role in feeding cities. The City is continually expanding and has become our main habitat. This is primarily due to the impacts of intensified globalization. Approximately half of the worlds population resides in cities. Urbanization has rapidly changed the face of the earth and the state of human life. By 2050, its estimated that the urban population will double. This will create an exponential increase in the amount of food consumption. Seoul is a prime example of globalization. After the 1960s there was a drastic increase in Seouls population. This was a result of changes made in the existing economic and social infrastructures. However, the rural areas in Korea did not develop at the same rate. There is a large gap between the supply and demand of food production and consumption. Rapid industrialization and urbanization patterns have strained arable land and as a result the farming population is in decline. The self-sufficiency rate of grain is now approximately 20 percent. Consequently, South Korea has become more sensitive to the world food market due to its increasing dependence on imported foods. It is impossible to maintain self-sufficiency, in relation to food production and consumption patterns. At this rate, food security will become unstable and will have an increasing effect on life, both physically and mentally. This thesis aims to propose an architectural design solution that will address the disconnection between food and urban development patterns. This proposal does not focus on economic, social, or political processes, but attempts to make a contribution in preparation for feeding the city of Seoul in a sustainable manner. Recently, some alternatives are being considered for stable food supply. These proposals deal with conserving and promoting agriculture policy, overseas agricultural base development, R&D, urban farming, etc. One of these alternatives, urban farming, was considered as a way to supply food to the city, introducing agriculture into urban areas in a sustainable way under the scope of architectural design. Garak Market was considered as an experimental design facility for urban farming. It is a primary source for residents to access food in the city, however, most of the food is produced in rural areas or is imported from abroad. Garak Market is the biggest wholesale market in Seoul, and is the epicenter of food distribution. This design experiment, proposes adding an urban farming function to the existing market. It will allow the market to function as a food production facility as well as a food distribution facility. Furthermore, this proposal will serve as a starting point in solving the decline in self-sufficiency, more particularly food security and reconnecting urban life to food in South Korea.Chapter 1 Introduction / Background 1 1.1 Food and City 1 1.2 Food in the city, Seoul 6 1.3 Farming in the city, Seoul 14 1.4 Farming for Garak Market in Seoul 15 Chapter 2 Urban Farming as an Alternative to feed a city 17 2.1 Outline of Urban Farming 17 2.2 Precedents of Urban Faming to feed a city 19 2.2.2 Victory Gardens 19 2.2.2 Howard, To-Morrow City 20 2.2.3 Cuba, Habana 22 2.3 Case study of Urban Farming Types 26 2.3.1 Ground Farm Type 26 2.3.2 Roof-Top Farm Type 30 2.3.3 Facade Farm Type 33 2.3.4 Mobile Farm Type 35 2.3.5 Hybrid Farm Type 36 2.4 Summary 39 Chapter 3 Understanding Garak Market 41 3.1 History of Garak Market 41 3.1.1 Opening of Garak Market 41 3.1.2 Expansion of Garak Market 42 3.1.3 Reconstruction of Garak Market 43 3.2 Role of Garak Market in Seoul 45 3.2.1 Outline of Food source in Garak Market 45 3.2.2 Food Distribution Process of Garak Market 46 3.3 Potential Area for Urban Farming in Garak Market 49 Chapter 4 Design Proposal 51 4.1 Design Strategy 51 4.1.1 Garak Market for Local Food Producer 52 4.1.2 Garak Market for Food Community 53 4.1.3 Expansion of Urban Farm to Urban Void 53 4.1.4 Maintaining Urban Farm to New Garak Market 54 4.2 Design Concept 56 4.2.1 Modules for Farming in Urban Area 57 4.2.2 Space Sharing System with Modules 60 4.2.3 Reuse of Existing Buildings for Urban Farming 64 4.3 Design in the Site 65 4.2.1 Programme Layout with Urban Contexts 65 4.2.2 Space Sharing System with Modules 66 4.2.3 Transformation of Existing Buildings 68 4.4 Summary 76 Chapter 5 Conclusion 82 Bibliography 85 Abstract (Korean) 89Maste

k-각형 곡선의 사영정규매몰과 미끈한 대수곡선 위의 선속의 정규생성

Thesis (doctoral)--서울대학교 대학원 :수리과학부,2003.Docto

Gross motor changes following selective posterior rhizotomy in children with cerebral palsy

보건학과/석사[영문] [한글] 이 연구의 목적은 뇌성마비아동에 있어 GMFM(gross motor function measure) 평가도구 를 이용하여 선택적 척수 신경 후근 절단술 전·후의 운등능력의 변화를 알아보는데 있다 . 연구대상은 1990년 3월부터 1993년 4월까지 연세대학교 의과대학 부속 재활병원에 입원 하여 선택적 척수 신경 후근 절단술(selective posterior rhizotomy)을 시술받은 24명의 뇌성마비아동을 대상으로 수술전과 수술 6개월후의 전체 운동능력 점수와 각 영역별 운동 능력 점수의 변화를 관찰하였다. 이 연구의 결과는 다음과 같다. 첫째, 수술후 전체 운동능력 점수는 수술전에 비해 평균 7.91점이 향상되었다(P<0.01). 둘째, 각 영역별 운등능력 변화점수는 눕기와 뒤집기 영역은 수술전·후 모두 100점으 로 차이가 없었고, 앉기 영역은 평균 5.95점, 네발기기와 무릎서기 영역은 평균 6.75점, 서기 영역은 평균 14.79점, 걷기·달리기·뛰기 영역은 평균 12.33점의 향상이 있었으며 서기 영역에서 가장 큰 향상을 나타냈다(P<0.01). 세째, 운동능력 변화점수는 수술전 독립보행 불능군이 보행가능군 보다 5.75점 높았다( p<0.05). 네째, 수술시기는 5세 이하의 연령군에서 가장 높은 운동능력 점수의 향상을 보였다(p< 0.05). 다섯째, 지능과 운동능력 점수 변화는 관련성이 없었다(p>0.05). 여섯째, 뇌성마비 분류에 따른 운동능력 점수의 변화는 경직성 양마비에서 증가를 보였 으나 통계적 유의성은 없었다. 이상의 결과로 미루어 볼때 선택적 척수 신경 후근 절단술은 수술의 적응증을 신중하게 적용하고 수술후 집중적인 재활치료를 하면 뇌성마비 아동에서 운동능력의 향상을 기대 할 수 있으며, 독립보행 불능군과 5세전에 수술한 경우 많은 향상을 기대할 수 있다. Gross motor changes for lowing selective posterior rhizotomy in children with cerebral palsy Young Rok Kim Graduate School of Health Science and Management Yonsei University (Directed by Professor Chang Il Park, M.D., Ph.D.) This study was designed to evaluate the change of gross motor function following selective posterior rhizotomy in children with cerebral palsy. In this study, 24 children with cerebral palsy, ranging in age at surgery from 3 to 12 years(avg. 6.9), were selected. They had had surgery in which the selective posterior rhizotomy was performed at Yonsei University Medical center. They were admitted for rehabilitation in the Yonsei University Rehabilitation Hospital between March 1990 to April 1993. This study measured the gross motor changes in subjects both one week prior to surgery and 6 months after surgery. The measurement tool used was the GMFM(gross motor function measure) scale. The data were analyzed by Wilcoxon signed rank test, Mann-whitney test, Kruskal-Wallis test. The results were as follows: 1. The total gross motor mean score difference between the pre-operative and 6 months post-operative score was 7.91 (P<0.01). 2. Gross motor scores were analysed in each of 88 conditions, lying, sitting, crawling, walking etc. Lying & Rolling scores remained unchanged. Improvement was seen in Sitting scores(5.95 p<0.01), Crawling & Kneeling (6.75 p<0.01), Standing(14.79 p<0.01), Walking·Running·Jumping (12.33 p<0.01). The greatest improvement was seen in standing scores. 3. The total mean change in GMFM scores before and after surgery showed a greater increase (5.75 higher, p<0.05) in the non-ambulatory group than the ambulatory. According to condition, the non-ambulatory/ambulatory total wean change (pre and 6 mos. post surgery) difference when compared were as for laws: Lying & Rolling : no difference: non-ambulator improved over ambulators in Sitting, Crawling & Kneeling and Standing by mean score difference of 11.65(p<0.01), 10.36(p<0.05), and 9.78(p<0.05) respectively. However, in Walking·Running·Jumping, the ambulatory group mean scores were higher by a mean of 2.30. 4. The most improved outcome (regardless of ambulation status) was found in the below 5 year age group(p<0.05). 5. IQ was not a relevant factor(p>0.05). 6. While there was a difference in the improvement between CP type scores, the small number of subjects precludes statistical inference. These results showed that selective posterior rhizotomy combind with intensive post surgery rehabilitation for children with cerebral palsy had a significant effect on gross motor function. However, further studies with long tern fort low-up and larger sample size should be done to show more definitive results.restrictio

An Analysis of the Main Factors Influencing Central Government Ministry Performance Management: A Case Study of MEST and MLTM in Korea

본 연구의 목적은 우리나라 정부 부처수준에서 수행되고 있는 성과관리제도에 영향을 미치는 요인들을 밝혀 성과관리제도가 현실에서 보다 실효적으로 작동할 수 있도록 제도를 설계하는데 정책적 시사점을 제공하기 위함이다. 이를 위해 선행연구 분석을 통해 각 영역에서 대표 사례(교육과학기술부, 국토해양부)를 선정하여 예시 분석을 실시하였다. 이러한 작업은 성과관리 제도가 성공적으로 현실에서 작동하기 위해 필요한 요소는 무엇이고, 그것을 제약하는 요인들을 밝혀내기 위함이다. 이를 위해 본 논문은 세가지 차원에서 사례 분석을 실시하였다. 첫째, 정책 및 성과정보 특성이라는 측면에서 교육과학기술부는 프로그램의 유형성이 낮게 측정되었고, 성과관리에 대한 조직 구성원들의 인식 전환이 필요한 것으로 지적되었다. 한편, 국토해양부는 높은 유형성을 나타냈음에도 불구하고, 정량적 사업 성과에 대한 체계적 관리시스템이 부재하였다. 둘째, 조직적 특성상의 요인을 지적할 수 있다. 먼저 조직 규모와 정책 실행조직의 구조가 성과관리에 있어서 주요한 변수로 작용하고 있다. 방대한 조직이나 예산 규모만큼 다양한 가치와 목적이 함축되어 있는 곳이 교육과학기술부이다. 반면 국토해양부는 교육과학기술부에 비해 정책적 목표가 비교적 명확하며, 정책의 최종 산출물 역시 매우 유형적으로 분석되었다. 셋째, 외부 환경적 요인과 성과관리와의 관계이다. 교육과학기술부의 정책 영역은 주지하는 바대로 우리나라에서 정치적 이념 대립이 가장 치열한 부처이고, 따라서 정치권력의 영향이 매우 높은 분야라고 할 수 있다. 반면에 전반적으로 국토해양부 소관 사업들은 정치권, 미디어 등의 영향에서 다른 정책 영역에 비해 상대적으로 자유롭다고 볼 수 있다. 따라서 갈등관계가 적은 국토해양부 사업은 외부 효과에 자유롭고, 이는 성과관리에 유리한 조건을 조성하게 되는 것이다. The purpose of this case analysis was to identify the elements necessary for the successful operation of and factors that hinder performance management in reality. The results of the study follow. First, performance management appropriateness, the most critical element in performance budgeting-based PART, was calculated for every institution. Secondly, organizational and policy traits were pointed out as factors that have a greater influence on performance management. The size of an organization and the structure of the policy implementation body are crucial variables in performance management. The massive organizational size and complicated implementation structure at the two ministries subject to the case analysis were found to be obstacles to performance management. Last, the correlation between external/environmental factors and performance management needs to be noted. The policy sector of Korea`s Education, Science and Technology Ministry is among the most polarized in terms of political ideology, hence tremendously influenced by political power. On the other hand, projects in the Ministry of Land, Transport and Maritime Affairs seem to be less influenced by political circles and the mass media in comparison with other policy sectors. Therefore, undertakings by the Land, Transport and Maritime Affairs Ministry face less conflict and are relatively free from outside influences, thus creating an advantageous situation for performance management

Reliability study of organic nonvolatile resistive memory at elevated temperatures

학위논문 (석사)-- 서울대학교 대학원 : 물리·천문학부, 2016. 2. 이탁희.In this study, nonvolatile organic memory devices were fabricated by using PI:PCBM (polyimide (PI) and 6-phenyl-C61 butyric acid methyl ester (PCBM) as an active memory material with Al/PI:CPBM/Al structure. As changing temperature from room temperature to 470 K, PI:PCBM organic memory devices showed good nonvolatile memory properties in terms of distribution of ON state current and OFF state current, threshold voltage of OFF state to ON state transition, retention, and endurance. These organic memory devices exhibited excellent ON/OFF ratio (ION/IOFF >103) through more than 200 times ON/Off switching cycles, and maintained ON/OFF states for longer than 104 seconds without showing any serious degradation under the measurement temperature up to 470 K. The structural robustness against thermal stress was confirmed through TEM cross-sectional image and AFM image of active layer after retention test at 470 K during 10,000 seconds. This study demonstrated that the operation of organic memory devices under high temperatures was able to be controlled by the parameters which was already used for room temperature, and that the structure of organic memory devices was maintained during thermal stress. These results may make it possible the utility of nonvolatile organic memory devices for high temperature environments.Chapter 1. Introduction 1 1.1. Achievements of organic memory 1 1.2. Operation under thermal stress 2 Chapter 2. Experiments 3 2.1. Memory material preperation 3 2.2. Fabrication 4 2.3. Devices charaterization and measurement 6 Chapter 3. Results and Discussions 7 3.1. Operation Characteristics 7 3.1.1. Current voltage curves 7 3.1.2. ON/OFF current ratios 9 3.1.3. Conduction mechanism 10 3.2. Statistical data under temperature variation 12 3.2.1. ON current and OFF current statistics 12 3.2.2. Threshold voltage statictics 13 3.3. Thermal robustness 16 3.3.1. Electric operation robustness 16 3.3.2. Structural robustness 18 Chapter 4. Conclusions 21 Appendix 22 References 24 국문초록(Abstract in Korean) 27Maste

An Analysis of the Appropriateness of Performance Budgeting by Government Departments: The Development & Application of "Performance Measurement Appropriateness"

성과주의 예산제도(우리나라의 `재정사업 자율평가제도`)의 핵심은 정책의 성과를 평가하여 그 결과를 예산 배분에 반영하는 것이다. 그렇다면 그 정책은 과연 측정 가능한 것인지, 또한 정책 평가를 위한 수단이라고 할 수 있는 성과지표는 측정 가능한 것으로 구성되어 있는지를 밝히는 것은 필수적인 과정이라고 할 수 있다. 따라서 본 연구는 재정사업 자율평가를 수행하는 전 부처의 정책 유형을 분류하고, 성과지표의 적절성을 파악하여, 이를 토대로 `성과측정 적합도`를 개발하였다. 또한 기관별 `성과측정 적합도`를 산출하여 성과측정이 용이한 기관과 그렇지 않은 기관을 수치화하였다. 본 연구를 통하여 이론적 논의를 기반으로 한 선행연구에서 시도했던 정책의 분류와 성과관리와의 관계를 실증적으로 규명하였다. 또한 시차를 두고 성과관리 적합도를 측정하여 기관들의 사업 수행 성격이 어떻게 변하여 가는지, 혹은 성과지표의 적합도가 향상되는 지를 관찰하는 것은 향후에 성과관리와 관련하여 시사점을 줄 것으로 예상된다. This study aims to conduct an analysis of Korea`s case by designating policy types and performance indicator traits as variables made up of thekey issues proposed in previous studies regarding performance budgeting. The study identifies relevant ministries and policies subject to performance budgeting after appraising the suitability of the performance indicator and classifying the policy types at all of the ministries which employ the Performance Assessment Rating Tool (PART) in Korea. A scale of `Performance Measurement Appropriateness` was also developed for common use based on a suitability analysis of performance indicators set for unit projects in the execution process. As a result, a discriminative analysis of the performance measurement appropriateness of Korea`s central administrative agencies was worked out