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Part I. Synthesis and Application of α-Per(inter)halocarbonyl Compounds Part II. Development of Simple Predictive Models for Organic Reactions with Small Dataset and Minimal Features
No full textPart I. Synthesis and Application of α-Per(inter)halocarbonyl Compounds:
Geminal chlorofluorides are versatile synthetic precursors to various organofluorines with a tetrasubstituted carbon center. In this work, we reported the geminal chlorofluorination of 1,2-dicarbonyl compounds via the tandem deoxygenative electrophilic and nucleophilic halogenations. The rationally designed dealkylation-resistant phosphoramidite enabled the use of non-proton electrophiles and heteroatom-bearing 1,2-dicarbonyl compounds. As a result, α-keto esters (O), α-keto thioesters (S), α-keto N-acylindoles (N), and α-keto acylsilane (Si) were successfully transformed to doubly or triply hetero-functionalized tetrasubstituted carbon centers with excellent site-selectivity.
Subsequently, upon derivatization of geminal chlorofluorides with azide, we discovered the remarkable accelerating effect of the geminal fluorine substituent that enables the facile rearrangement of geminal azidofluorides into imidoyl fluorides without the typically required aid of strong acid under mild reaction conditions. The role of geminal fluorine was elucidated by both experimental and computational investigations. This new reactivity led to a practical one-step tandem preparative method for rarely known bench-stable imidoyl fluorides from a wide range of structurally diverse geminal chlorofluorides.
To expand beyond 1,2-dicarbonyl substrates, the electronically similar, synthetically and pharmaceutically valuable α-perfluoroketones were evaluated. However, the inherent challenges associated with the activation and discrimination of the C–F bonds typically lead to over-defluorination as well as functional group incompatibility. We addressed these problems by utilizing our group’s rationally designed organophosphorus reagent that promoted mild and selective manipulation of single C–F bond in trifluoromethyl and pentafluoroethyl ketones via an interrupted Perkow-type reaction, which allowed the replacement of fluorine with more labile and synthetically versatile congeners such as chlorine, bromine, and iodine. The resulting α-halo-perfluoro ketones have two reactive units with orthogonal properties that would be suitable for the subsequent structural diversification. DFT calculation identified the favorable P–F interaction as the crucial factor for both thermodynamic and kinetic viewpoints.
Part II. Development of Simple Predictive Models for Organic Reactions with Small Dataset and Minimal Features:
Machine learning (ML) is an emerging area in organic synthesis for the reaction design and prediction. In recent studies, the ML approach for reaction development using big data with many features provided the best reaction conditions for the optimal yields and stereoselectivities. Despite the high performance, the preparation of large datasets is often difficult, especially for non-specialists. In this study, simple ML models were developed by utilizing easily available and familiar 13C NMR chemical shifts of the reacting sites in the substrates for our geminal chlorofluorination. Upon training on small datasets (<150) with condensed features, the feed-forward neural network (FNN) model could predict the yields and site-selectivities with reasonable efficiency. Moreover, we observed a notaable improvement in performance upon removal of empirically less relevant features. Subsequently, our ML model was advanced through the utilization of an unusual tabular augmentation method for stereoselective geminal bromofluoroolefination by fitting the real datasets into sigmoid or logarithmic curves. With the augmented dataset, the prediction of reaction profiles with the FNN model was substantially improved. The linearly combined use of our augmentation technique and conditional tabular generative adversarial network (CTGAN) also enhanced the model even further.DoctorAbstract i
List of Contents iii
List of Schemes viii
List of Figures xii
List of Equations xv
List of Tables xvi
Synthesis and Application of α-Per(inter)halocarbonyl Compounds
I. Introduction 2
1.1. Geminal Chlorofluorination of Various 1,2-Dicarbonyl Compounds 2
1.1.1. Our Previous Works 2
1.1.2. Access to Multifunctionalized Tetrasubstituted Carbon Centers 8
1.1.3. Our Purpose for Geminal Chlorofluorination of 1,2-Dicarbonyl Compounds 9
1.2. Azidation and Fluorine-assisted Rearrangement of Geminal Chlorofluorides 12
1.2.1. Synthetic Utility and Preparative Method of Imidoyl Fluorides 12
1.2.2. Our Purpose for Azidation and Fluorine-assisted Rearrangement 13
1.3. Mono-defluorinative Functionalization of Perfluoroalkyl Ketones 14
1.3.1. Defluorinative Functionalization of α-Perfluoroalkyl Ketones 14
1.3.2. Our Purpose for Mono-defluorinative Functionalization of Perfluoroalkyl Ketones 16
II. Results and Discussion 18
2.1. Synthesis of Geminal Chlorofluorides via Kukhtin-Ramirez Reaction 18
2.1.1. Preparation of Various 1,2-Dicarbonyl Compounds 18
2.1.2. Initial Optimization with α-Keto Thioester 21
2.1.3. Optimization with Dealkylation-resistant Phosphorus Reagents 22
2.1.4. Reaction Scope – α-Keto Thioesters, Amides, and Acylsilanes 26
2.1.5. Reaction Scope – α-Keto Esters 34
2.1.6. Computational Study 35
2.1.7. Asymmetric Geminal Chlorofluorination 36
2.2. Azidation and Fluorine-assisted Rearrangement of Geminal Chlorofluorides 40
2.2.1. Preparation of Geminal Azidofluorides and a Defluoro Analogue 40
2.2.2. Quantitative Analysis and Mechanistic Studies 41
2.2.3. Reaction Condition Optimization 45
2.2.4. Reaction Scope – Aryl Migration 46
2.2.5. Reaction Scope – Alkyl and Benzoyl Migration 47
2.2.6. Scope Expansion 50
2.2.7. Synthetic Applications 51
2.3. Mono-defluorinative Functionalization of Perfluoroalkyl Ketones 54
2.3.1. Preparation of Perfluoroalkyl Ketones 54
2.3.2. Optimization of Defluorination 60
2.3.3. Optimization of Halogenations 68
2.3.4. Reaction Scope of Defluorinative Halogenations 70
2.3.5. Defluorinative Protonation 75
2.3.6. Other Functionalizations 79
2.3.7. Asymmetric Defluorinative Functionalizations 82
2.3.8. Computational Study 88
III. Conclusion 90
·
Development of Simple Predictive Models for Organic Reactions with Small Dataset and Minimal Features
IV. Introduction 93
4.1. Machine Learning with Small Dataset and Minimal Features 93
4.2. Our Purpose for Development of Simple Predictive Models for Organic Reactions 94
V. Results and Discussion 97
5.1. Prediction of Yield and Site-selectivity for Geminal Chlorofluorination 97
5.1.1. Model with All Descriptors 97
5.1.2. Model with Reduced Descriptors 98
5.1.3. Model with Simplified Substrates 100
5.2. Prediction of Reaction Profile for Geminal Bromofluoroolefination 102
5.2.1. Model with Real Data 102
5.2.2. Model with Augmented Data 104
5.2.3. Fitting with Kinetic Equations 109
VI. Conclusion 111
VII. Miscellaneous 112
7.1. Preparation of α-Phosphoniumoxy Enoxy Complex 112
7.2. Preparation of Oxazaphospholene 112
7.3. Preparation of Dioxaphospholene from Benzoin with Phosphorus(V) Reagent 116
7.4. Asymmetric Reduction of Benzil 117
7.5. Palladium-Catalyzed Coupling Reaction with Dioxaphospholene 117
7.6. 6π-Electrocyclization and Desymmetrization of Dioxaphospholene 118
7.7. Copper-catalyzed Cross-coupling of Geminal Chlorofluoride 120
7.8. Reductive Functionalization of Trifluoromethyl Ketones 120
7.9. Attempted Skeletal Editing of Phthalazine and Indole 127
7.10. Relayed Heteroatom Group Transfer of Bisthioester 130
VIII. Acknowledgements 131
IX. References 132
X. Experimental 144
10.1. General Experimental 144
10.2. Experimental Procedures 147
10.2.1. Geminal Chlorofluorination of 1,2-Diketones 147
10.2.1.1. Prepraration of 1,2-Diketones 147
10.2.1.2. Geminal Chlorofluorination of Aryl–Aryl Substrates 148
10.2.1.3. Geminal Chlorofluorination of Aryl–Alkyl Substrates 150
10.2.1.4. Preparation of α-Keto Amides 152
10.2.2. Geminal Chlorofluorination and Derivatization of α-Keto Thioester 153
10.2.2.1. Preparation of Phosphorus Reagents 153
10.2.2.2. Formation of Dioxaphospholene 159
10.2.2.3. Geminal Chlorofluorination 162
10.2.2.4. Derivatization of Geminal Chlorofluorides 163
10.2.3. Geminal Chlorofluorination of α-Keto Acylsilane 166
10.2.3.1. Preparation of Alkynyl Silanes 166
10.2.3.2. General Procedure A for Preparation of α-Keto Acylsilanes 168
10.2.3.3. General Procedure B for Preparation of α-Keto Acylsilanes 170
10.2.3.4. Formation of Dioxaphospholene 171
10.2.3.5. Geminal Chlorofluorination 173
10.2.4. Geminal Chlorofluorination and Derivatization of α-Keto Acylindoles 174
10.2.4.1. Preparation of α-Keto Acylindoles 174
10.2.4.2. Formation of Dioxaphospholene 176
10.2.4.3. Geminal Chlorofluorination 177
10.2.4.4. Derivatization of Geminal Chlorofluorides 177
10.2.5. Asymmetric Geminal Chlorofluorination 178
10.2.6. Azidation and Fluorine-assisted Rearrangement of Geminal Chlorofluorides 181
10.2.6.1. Preparation of Geminal Azidofluorides 181
10.2.6.2. Azidation and Rearrangement of Geminal Chlorofluorides 184
10.2.6.3. Derivatization of Imidoyl Fluorides 185
10.2.7. Mono-defluorinative Functionalization of Perfluoroalkyl Ketones 186
10.2.7.1. Preparation of Substrates from Aldehydes 186
10.2.7.2. Preparation of Substrates from Acids 188
10.2.7.3. Preparation of Substrates via Acylation and N–H Protection 196
10.2.7.4. Preparation of Substrates from Perfluoroalkyl Esters 198
10.2.7.5. Attempted Substrate Preparations 199
10.2.7.6. Defluorination 202
10.2.7.7. Defluorinative Halogenation 209
10.2.7.8. Defluorinative Protonation and Deuteration 227
10.2.7.9. Defluorinative Alkylation 234
10.2.7.10. Preparation of Chiral Catalysts 236
10.3. Miscellaneous 242
10.3.1. Preparation of Monoximes 242
10.3.2. 6π-Electrocyclization and Desymmetrization of Dioxaphospholene 243
10.3.3. Reductive Functionalization of Trifluoromethyl Ketones 246
10.3.4. Skeletal Editing of Phthalazine and Indole 250
10.4. DFT Calculations 251
10.5. Preparation of Datasets and Models 256
10.5.1. Predictive Models for Geminal Chlorofluorination 256
10.5.2. Predictive Models for Geminal Bromofluoroolefination 256
10.6. Experimental References 268
Curriculum Vitae 272
Appendix: NMR Spectra 27
Two-level system loss characterization of NbTi superconducting resonators on Si/SiO2 substrates
No full textSuperconducting coplanar waveguide (SCPW) resonators, key components for quantum computing and sensing applications, require a high internal quality factor (Qi) for effective qubit readout and quantum sensing applications. Minimizing two-level system (TLS) losses, particularly at material interfaces, is critical for gatemon and topological qubits operating at low temperatures and in high magnetic fields. NbTi, a superconducting alloy with a high upper critical field, enables SCPW resonators resilient to such conditions. We fabricated NbTi SCPW resonators on Si/SiO2 substrates and systematically characterized their TLS-limited quality factors as functions of temperature and microwave photon number. Our results demonstrate that NbTi-based SCPWs on Si/SiO2 substrates provide a promising platform for developing next-generation quantum circuits. © 2025 The AuthorsTRUEsciescopuskc
Development of a Thin Three-Dimensional Ag Gradient Cu-Separator Scaffold for Stable and High-Energy Lithium Metal Batteries
No full textAdopting three-dimensional (3D) scaffolds onto lithium metal anode has emerged as a promising strategy to improve the charge/discharge stability of next-generation high-energy-density lithium metal batteries (LMBs). However, the undesirable growth of Li dendrites on the scaffold’s surface and their high-cost fabrication methods remain challenging. To address these issues, herein, a functional 3D scaffold employing a lithiophilic Ag concentration gradient (3D Ag@Cu) is designed, which can be prepared via a simple galvanic displacement. The lithiophilic Ag reacts with Li to form a solid solution, reducing the Li nucleation overpotential and promoting uniform Li deposition. Furthermore, the Ag-gradient structure facilitates the bottom-up growth of Li within the scaffold, maximizing the use of the internal space. Consequently, a full-cell equipped with the 3D Ag@Cu scaffold demonstrated higher cycling stability (89.03% capacity retention after 110 cycles) and rate performance (65.6% capacity retention at 2 C) compared to both LMBs with the planar Cu foil and the bare 3D Cu scaffold. © 2025 American Chemical Society.FALSEsciescopu
Development of an Integrated Molecular and Immunodiagnostic Paper Chip Technology Ji-Ho Park College of Natural Sciences
No full textPoint-of-care testing (POCT) technologies that enable rapid, equipment-free diagnostics are essential for improving healthcare accessibility, particularly in resource-limited settings. As the demand for portable, user- friendly, and cost-effective diagnostic platforms continues to rise, the development of integrated POCT systems has gained increasing attention. Among the diagnostic methods considered suitable for POCT, isothermal nucleic acid amplification has emerged as a powerful alternative to conventional PCR. In particular, loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA) have garnered significant interest due to their ability to rapidly amplify target nucleic acids under constant temperature conditions, eliminating the need for thermal cyclers. Alongside molecular diagnostics, immunoassays play an essential role in detecting disease-related proteins directly from biological samples. Among various immunoassay formats, lateral flow assays (LFAs) are especially attractive for POCT applications due to their rapid turnaround, equipment-free operation, and low manufacturing cost. To address their inherent sensitivity limitations, automated signal amplification approaches have been explored. To effectively implement both molecular and immunoassays in a compact and low-cost format, paper-based diagnostic platforms have drawn increasing attention. Paper allows for passive fluid transport and patternable surface properties, enabling the integration of complex biochemical workflows in a simplified and scalable structure without requiring external equipment. In Chapter 2, a USB-powered portable diagnostic device integrating LAMP and LFA was developed. The device was designed to carry out a 25-minute LAMP reaction, followed by the opening of a wax valve after approximately 5 minutes to allow fluid flow through the detection strip. A custom-printed circuit board (PCB) and heating module were fabricated to automate the entire process, enabling fully integrated amplification and colorimetric signal detection. Using this system, two major foodborne pathogens were successfully detected: Vibrio vulnificus at concentrations as low as 120 CFU per reaction and Salmonella Typhimurium at concentrations as low as 60 CFU per reaction. In Chapter 3, a portable diagnostic platform integrating recombinase polymerase amplification (RPA) with LFA was developed, powered by a 3.7V lithium-polymer battery. The device incorporates an automatic fluid- switching system based on water-swellable polymers, allowing fully automated assay progression upon two sequential solution injections at the beginning of the test. This enables nucleic acid-specific amplification, on-chip capture of amplified products, and visualization of the signal without intermediate step. Using this platform, SARS-CoV-2 was successfully detected with a sensitivity of 10 copies/µL within 30 minutes. In Chapter 4, to address the limitations of the RPA-based device described in Chapter 3, a LFA-integrated portable device was developed to reproduce benchtop-level performance. The system was designed to support liquid-phase RPA reactions and employed a vertical wax valve to enable automated fluid progression and signal visualization after amplification. The developed device demonstrated sensitive detection of SARS-CoV-2 down to 1 copy/µL. Furthermore, clinical validation was conducted using 20 respiratory infection patient samples. Among them, five healthy samples and five influenza A virus samples yielded negative results, while all ten SARS- CoV-2 patient samples tested positive, confirming high specificity and sensitivity of the system. In Chapter 5, a chemical signal amplification strategy was investigated to overcome the inherent sensitivity limitations of conventional LFA. Among various signal enhancement techniques, the in situ growth of gold nanoparticles via chemical reduction is widely adopted to intensify colorimetric signals. In this study, a novel automation approach was introduced by applying a surfactant-triggered delayed release mechanism using the hydrophobic properties of office paper. This system enabled automated signal enhancement to occur approximately 10 minutes after the initiation of the immunoassay, all triggered by a single solution drop. The developed LFA strip was applied to the detection of cardiac troponin I, a key biomarker for acute myocardial infarction, achieving a detection limit as low as 2.42 pg/mL—representing a 157-fold improvement in sensitivity compared to assays without enhancement. Furthermore, clinical validation using six patient samples demonstrated successful detection even in previously undetectable cases, highlighting the potential of this method to improve diagnostic outcomes in low-concentration clinical scenarios.DoctorAbstract i
List of contents iii
List of tables v
List of figures vi
I. INTRODUCTION 1
1. 1. Point-of-care testing (POCT) 1
1. 2. Nucleic acid amplification testing (NAAT) 5
1. 3. Immunoassay 11
1. 4. Paper-based diagnostic platform 15
1. 5. Research purpose and strategy 18
II. LAMP-based POCT device: USB-Powered lab-on-paper platform 20
2. 1. Introduction 21
2. 2. Materials and Methods 23
2. 2. 1. Materials and reagents 23
2. 2. 2. Preparation of Lab-on-paper (LOP) 23
2. 2. 3. Operation of LOP 24
2. 2. 4. Calculation the signal of test line 24
2. 2. 5. Temperature measurements 25
2. 2. 6. Colored solution for flow analysis 25
2. 2. 7. Bacteria culture & Preparation of bacteria spiking samples 26
2. 2. 8. LAMP reaction in the LOP platform 27
2. 3. Results and Discussion 28
2. 3. 1. Overview of Lab-on-paper (LOP) device 28
2. 3. 2. Operation principle of the LOP device 29
2. 3. 3. Molecular diagnostics of bacteria from spiking food sample 30
2. 3. 4. Quantitative analysis of food-poisoning bacteria in the LOP system 31
2. 4. Conclusion 32
III. RPA-based POCT device: Automated fluid switching system for visualization of RT-RPA
reaction
3. 1. Introduction 44
3. 2. Materials and Methods 46
3. 2. 1. Sources of reagents and materials 46
3. 2. 2. RT-RPA reaction 46
3. 2. 3. Production of the NiCr thin film 46
3. 2. 4. Optimization of the RT-RPA reaction on the NiCr thin-film heater 47
3. 2. 5. Preparation of the battery and electric circuit 47
3. 2. 6. Preparation of the paper chip 47
3. 2. 7. Preparation of antibody-gold nanoparticle (AuNP) conjugates 48
3. 2. 8. Delayed release of the AuNP conjugate using a swellable polymer 48
3. 2. 9. Operation of the paper-based rapid NAAT device 48
3. 3. Results and Discussion 49
3. 3. 1. Schematic representation of the device and mechanism 49
3. 3. 2. Primer design and screening 49
3. 3. 3. Characterization of the NiCr thin-film heater 50
3. 3. 4. Production of the paper chip and characterization of its application for the RT-RPA
reaction 51
3. 3. 5. Preparation of antibody-AuNP conjugate and optimization of delayed-release platform
for automated visualization 51
3. 3. 6. Detection of SARS-CoV-2 RNA using the portable RT-RPA kit 52
3. 4. Conclusion 71
IV. RPA-based POCT device: A Portable RPA-LFA Integrated Device
4. 1. Introduction 73
4. 2. Materials and Methods 75
4. 2. 1. Sources of reagents and materials 75
4. 2. 2. Preparation of RPA (Recombinase Polymerase Amplification 75
4. 2. 3. Gel Electrophoresis 76
4. 2. 4. Conjugation of Antibodies to AuNPs 76
4. 2. 5. Fabrication of strip in disposable cartridge 76
4. 2. 6. Fabrication of a plastic compact heater case 77
4. 2. 7. Design of the Electrical Circuit 77
4. 2. 8. Fabrication of Paraffin Wax-Coated Wipes 77
4. 2. 9. Dipstick Assay for Colorimetric Detection 77
4. 2. 10. Measurement of Heater Setting Temperature and Actual Solution Temperature Using
an Infrared Camera 78
4. 2. 11. Temperature Measurement of Carbon Heater 78
4. 2. 12. Operation of the RPA-LFA One-Hole Kit 78
4. 3. Results and Discussion 79
4. 3. 1. Schematic representation and principle of developed portable device 79
4. 3. 2. Design and Evaluation of the Vertical Wax Valve 79
4. 3. 3. Implementation of a Sandwich Immunoassay for Colorimetric Detection of RT-RPA
Amplicons 80
4. 3. 4. Design and Optimization of a Portable Heating Cartridge Circuit 81
4. 3. 5. SARS-CoV-2 Detection and Clinical Validation Using the Portable RT-RPA
Device 82
4. 4. Conclusion 94
V. Lateral flow assay based immunodiagnosis: Automated signal enhancement using office
paper.
5. 1. Introduction 96
5. 2. Materials and Methods 98
5. 2. 1. Source of reagents and materials 98
5. 2. 2. SEM imaging and EDS analysis of office paper 98
5. 2. 3. Contact angle measurement 98
5. 2. 4. Preparation of AuNP-Antibody conjugate 99
5. 2. 5. Fabrication of automated signal enhancement strip 99
5. 2. 6. 3D modeling and printing of the case 100
5. 2. 7. Validation of the strip using human serum spiked cTnI 100
5. 2. 8. Clinical sample-based validation 100
5. 3. Results and Discussion 101
5. 3. 1. Hydrophobicity of the office paper and surfactant 101
5. 3. 2. Overview of the Surfactant-triggered signal enhancement 102
5. 3. 3. Surfactant-triggered reagent release through hydrophobic barrier 102
5. 3. 4. Regulation of secondary flow timing via surfactant and barrier thickness 103
5. 3. 5. Validation of the developed strip in a sandwich immunoassay for cTnI
detection 103
5. 4. Conclusion 114
Vi. Summary and Conclusion 115
Vii. References 11
Spectrally Tunable 2D Material‐Based Infrared Photodetectors for Intelligent Optoelectronics
No full textThe evolution of intelligent optoelectronic systems is driven by artificial intelligence (AI). However, their practical realization hinges on the ability to dynamically capture and process optical signals across a broad infrared (IR) spectrum. Central to this capability are IR photodetectors (PDs) based on 2D materials (2DMs), which offer tunable spectral responsivity and wavelength‐resolved multiparameter optical information. This review examines the fundamental mechanisms and design strategies that enable spectral tunability at the frontier of 2DM‐based IR PDs, elucidating how they offer unique opportunities to tailor spectral responses across a broad wavelength range through symmetry‐breaking induced by geometric (geometrically tunable spectral engineering) and electric‐field (electrically tunable spectral engineering) effects. These approaches collectively enable simultaneous optimization of spectral tunability and sensitivity without compromising wavelength coverage, speed, power efficiency, or scalability, while also providing polarization sensitivity, multiband detection, and self‐powered operation for edge‐integrated AI platforms, including computational spectroscopy, artificial vision, computing, and communications. This review outlines the key processes and integration requirements for scalable manufacturing, which are essential for establishing spectrally tunable 2DM‐based IR PDs as core building blocks of intelligent optoelectronics. Ultimately, the development of spectrally tunable 2DM‐based IR PDs will transform intelligent optoelectronic platforms for or withAITRUEsciescopu
Area Efficient CFET SRAM and High PFOM Ga2O3 Power Transistor Design via In-House TCAD Process and Device Simulation
No full text반도체소자는전기신호를제어할수있는특성덕분에컴퓨팅,정보저장,전력기기등 현대사회를구성하는기술들에필수적인역할을수행해왔다.이중컴퓨팅용로직반도체 기술은지난수십년간트랜지스터채널의길이를줄이는방향으로기술의발전을지속해 왔다.그러나,최근에는누설전류증가와같은문제로인한물리적인한계로인해채널의 길이를더이상줄이기힘들어졌고,이에따라집적도향상을지속하기위한새로운해결 책이 요구되고 있다. 대표적으로 트랜지스터를 효율적으로 배치할 수 있는 새로운 소자 구조들이 많은 주목을 받고 있다. Forksheet FET (FSFET)은 NMOSFET과 PMOSFET 사 이간격을줄이는것을통해전체셀의면적을감소시켜,트랜지스터의집적도를향상시킬 수있을것으로기대가되고있다.하지만,줄어든간격으로인해공정변수,특히기판도 핑공정에대한민감성이증가하여,기판부분의기생채널로누설전류가흐르는문제가 발생할 수 있어 이를 방지할 수 있는 구조가 요구된다. 집적도 향상을 위한 또 다른 구조 로는 NMOSFET과 PMOSFET을수직으로적층하는 complementary FET (CFET)구조가 있다. CFET은기존에같은층에배치되던 NMOSFET과 PMOSFET을적층하여집적도를 향상시킬수있는장점이있다.하지만, CFET은 NMOSFET과 PMOSFET이쌍을이루기 때문에, 불균형한 개수의 NMOSFET과 PMOSFET을 사용하는 SRAM 설계 과정에서 면 적이비효율적으로사용되는문제가발생할수있다.전력기기에사용되는전력반도체의 경우높은안정성과성능을위해기존의실리콘보다우수한특성을가지는재료를사용한 소자에대한연구가많이진행되고있다.산화갈륨 (Ga2O3)은탄화규소 (SiC)나질화갈륨 (GaN)보다더넓은밴드갭,높은항복전계값,열적안정성덕분에차세대전력반도체물 질로서주목받고있다.하지만, p-타입도핑의어려움으로인해기존의트랜지스터구조를 사용할수없는단점이있어,높은성능과안정성을가지는새로운산화갈륨반도체소자 구조가 요구되고 있다. 평면형 게이트를 가지는 수직형 산화갈륨 MOSFET 구조는 다른 구조들에 비해 높은 안정성과 항복 전압을 가질 수 있는 장점이 있지만, 소자의 성능이 트랩을형성하는질소이온주입공정에크게영향을받는문제가있다. 본학위논문에서는인하우스 TCAD시뮬레이터를구현한후,이를이용하여로직반 도체소자,산화갈륨전력반도체소자의설계를진행하였다.먼저,공정조건에따라로직 반도체 소자의 구조를 생성하기 위해 level-set method 기반으로 3차원 공정 시뮬레이터 를 구현하고 기존에 개발되었던 소자 시뮬레이터와 통합하는 일을 수행하였다. 이는 2 장에서 다루어진다. 구현한 시뮬레이터를 활용하여 크게 2가지 로직 반도체 소자에 대 한 연구를 진행하였다. 첫 번째로 누설 전류 방지를 위해 하부 유전체 절연막을 가지는 FSFET 소자에 대한 공정 및 소자 시뮬레이션을 진행하였다. FSFET 소자의 하부 유전체 를형성하는과정에서게이트산화막이병합되는문제가발생하게되는데,이를방지하기 위해 IMEC에서 얇은 실리콘 분리막을 도입한 구조가 제안되었다. 그러나, 구체적인 실 험이나 시뮬레이션 결과는 제공되지 않았기에, 본 연구에서는 이에 대한 구체적인 공정, 소자시뮬레이션을진행하였다. TCAD소자및공정시뮬레이션을통해실리콘분리막이 게이트 산화막의 병합 문제를 해결하면서도 소자의 성능을 저하하지 않는 것을 확인하 였다.위내용은 3장에서다루어진다.두번째로 4장에서는공간비효율문제를해결하기 위한 3P3N SRAM 구조를 제안한 후, 이에 대한 시뮬레이션을 진행하였다. 3P3N SRAM 구현을 위해 스플릿 게이트 공정을 제안한 후 이에 대한 시뮬레이션을 진행하였다. 이후 소자 시뮬레이션을 통해 특성을 평가하였고, 기존의 SRAM과 유사한 성능을 가지면서 14% 더 적은 면적을 가지는 SRAM을 설계하였음을 확인하였다. 마지막으로 5장에서는 TCAD시뮬레이션을기반으로평면게이트를가지는산화갈륨수직형 MOSFET소자에 대한 공정 조건 최적화를 진행하였다. 항복 원인을 분석한 후, 항복 전압을 높이기 위해 트랩을 형성하는 질소의 이온 주입 공정 조건을 최적화하였다. 최적화를 통해 기존의 소 자보다 173배높은전력성능지수를가지는소자를설계하였다. ©2025 김인기 ALL RIGHTS RESERVED|Semiconductor devices have played an essential role in modern technologies such as comput- ing, data storage, and power devices, due to their ability to control electrical signals. Among these, logic semiconductor technology for computing has advanced over the past few decades by reducing the channel length of transistors. However, due to physical limitations, such as the increase in leakage current, it has become increasingly difficult to further reduce the chan- nel length. As a result, new solutions are needed to continue improving integration density. In particular, new device architectures that allow for more efficient transistor arrangement have been gaining attention. The forksheet FET (FSFET), for example, is expected to improve in- tegration density by reducing the spacing between NMOSFET and PMOSFET devices. How- ever, the reduced spacing makes the process more sensitive to variations, leading to issues such as leakage current due to parasitic channels in the substrate, which requires a structural solution to prevent. Another structure that aims to improve integration density is the com- plementary FET (CFET), which vertically stacks NMOSFET and PMOSFET devices. This allows for greater integration density by stacking transistors that were previously placed on the same plane. However, since CFET pairs NMOSFETs and PMOSFETs, it can lead to inefficient use of area in the design of static random access memory (SRAM), which often requires an unbalanced number of NMOSFETs and PMOSFETs. For power semiconductors used in power devices, research has increasingly focused on devices made from materials with superior properties compared to conventional silicon, in order to achieve high relia- bility and performance. Gallium oxide (Ga2O3) has attracted attention as a next-generation power semiconductor material due to its wider bandgap, higher breakdown field, and better thermal stability compared to silicon carbide (SiC) and gallium nitride (GaN). However, the difficulty in achieving p-type doping presents a drawback, as it prevents the use of conven- tional transistor structures. Therefore, there is a need for novel Ga2O3 device structures that can achieve high performance and reliability. Vertical MOSFETs with a planar gate structure have the potential of higher stability and breakdown voltage compared to other structures, but their performance is heavily affected by the ion implantation process that forms traps. In this dissertation, logic and Ga2O3 power semiconductor devices are designed through an in-house TCAD simulator. First, A three-dimensional process simulator based on the level-set method was developed to generate logic semiconductor structures according to pro- cess conditions, which is discussed in Chapter 2. Using the simulator, two main studies on logic semiconductor devices were conducted. In the first study, process and device simula- tions were performed for FSFET devices with a bottom dielectric isolation (BDI) to prevent leakage current. The simulations revealed that the gate oxide layers tended to merge during the formation of the bottom dielectric. To address this issue, IMEC proposed a structure in- corporating a thin silicon separator. In this study, the impact of the silicon separator on both the fabrication process and the device’s electrical characteristics was systematically investi- gated through TCAD process and device simulations. This is discussed in Chapter 3. In the second study, covered in Chapter 4, single-ended 3P3N CFET SRAM structure was proposed to solve the spatial inefficiency problem and conducted simulations on this design. A split- gate process was proposed for implementing the single-ended structure and simulations was conducted to evaluate its characteristics. The simulations showed that the proposed SRAM structure occupies 14% less area while achieving performance comparable to that of conven- tional SRAMs. Finally, in Chapter 5, I performed optimization of nitrogen ion implantation process condition for a Ga2O3 vertical MOSFET with a planar gate structure using TCAD simulation. After analyzing the causes of breakdown, the nitrogen ion implantation process that forms traps was optimized to improve the breakdown voltage. The optimized device ex- hibited a power figure of merit (PFOM) 173 times higher than that of reported Ga2O3 vertical MOSFET. ©2025 In Ki Kim ALL RIGHTS RESERVEDDoctorList of Contents
Abstract (English) i
Abstract (Korean) iv
List of contents vii
List of figures x
List of tables xvii
1 Introduction 1
1.1 Background 1
1.1.1 CMOS scaling 1
1.1.2 Power transistors 5
1.2 TCAD simulation 6
1.3 Thesis overview 9
2 Development of 3D Process Simulator Based on Level-Set Method 11
2.1 Introduction 11
2.1.1 Motivation of 3D TCAD process simulator 11
vii
2.1.2 Level-set method for topology simulation 12
2.2 3D process simulation framework based on level-set method 15
2.2.1 Initialization 15
2.2.2 Sparse filed level-set method for efficient time evolution 16
2.2.3 Multi-level-set method 18
2.2.4 Explicit boundary generation with marching cube method 21
2.2.5 Bulk mesh generation 25
2.3 Process simulation example 26
2.3.1 Anisotropic etching 26
2.3.2 Isotropic process 26
2.3.3 Chemical mechanical polishing (CMP) process 27
2.3.4 Crystallographic selective expitaxial growth 28
3 Bottom Dielectric Isolation Forksheet FETs with a Si Separator 30
3.1 Introduction 30
3.2 Process emulation 32
3.3 Device simulation results and discussion 39
3.4 Conclusion 42
4 Single-Ended 3P3N CFET SRAM 43
4.1 Introduction 43
4.2 3P3N SRAM cell 43
viii
4.3 Area efficiency 45
4.4 Process for a split-gate device 46
4.5 Scaling trend 49
4.6 Device simulation 50
4.7 Discussions 52
4.8 Conclusion 53
5 Ga2O3 Vertical MOSFET with High PFOM 54
5.1 Introduction 54
5.2 Process simulation of Ga2O3 verticalMOSFET 57
5.3 Result and discussion 62
5.3.1 Device simulation setup 62
5.3.2 Input characteristics 63
5.3.3 Breakdown simulation 67
5.3.4 PFOM optimization 71
5.4 Conclusion 74
6 Conclusion 76
References 79
Acknowledgements 95
i
Efficient high-power continuous-wave multi-slab Fe:ZnSe laser at 4.1 µm
No full textWe report high-efficiency continuous-wave operation of a cryogenically cooled Fe2+:ZnSe laser at 4.167 µm using a four-slab configuration (2.75 mm each, 4.3-7.9 × 1018 cm−3) optimized for pump absorption and gain distribution. Cooled to 90 K and double-end pumped at 2.832 µm by two fiber-bulk hybrid Cr:ZnSe lasers (17 W and 13 W), the system achieved complete pump absorption (ηa ≈ 99.68%), delivering 13.9 W output with 41% slope efficiency. Beam quality was near diffraction-limited (M2X = 1.13 ± 0.11, M2Y = 1.24 ± 0.12). The lasing wavelength red-shifted from 4.036 to 4.167 µm with power, attributed to thermal and gain-spectrum dynamics. This architecture mitigates thermal lensing and supports efficient mid-infrared power scaling. © 2025 Elsevier B.V., All rights reserved.TRUEsciescopu
Influence of Nighttime Chemical Processes on Daytime Oxidation through ClNO2
No full textNitryl chloride (ClNO2) can play a significant role in local daytime atmospheric oxidation as a major source of chlorine (Cl) radicals. Previous field studies have reported a wide range of ClNO2 concentrations across various regions, suggesting that Cl radical production may also vary substantially. However, our understanding of the underlying causes of this variability in ClNO2 concentrations and the corresponding impacts on atmospheric oxidation remain poorly constrained.
This dissertation aims to investigate the chemical processes governing ClNO2 concentrations and its oxidative effects, based on intensive field observations conducted in Gwangju, South Korea, during the winter of 2022-2023. Specifically, the role of ClNO2 in enhancing daytime ozone (O3) production during the campaign was evaluated and found to be effective even through the afternoon. Additionally, the contributions of relevant chemical and meteorological parameters controlling ClNO2 abundances were assessed. This analysis revealed that nocturnal O3 availability served as a limiting factor for ClNO2 concentration in this campaign. Moreover, a simplified model capable of estimating ClNO2 production rates even without direct ClNO2 measurement was developed and validated in not only this campaign but also under various environmental conditions. Finally, to clearly establish the applicable conditions of the developed model, a broadband cavity-enhanced absorption spectrometer for the precise measurement of nitrate (NO3) radicals was built and deployed in the field. This research provides a scientific basis for understanding nighttime and daytime chemistry as an integrated process mediated by ClNO2, and for interpreting the variability of ClNO2 concentrations and the resulting impacts on atmospheric oxidation.DoctorAbstract i
List of Tables v
List of Figures vi
Ⅰ. Introduction 1
1.1. Summary of previous work 1
1.2. Overview of this work 3
Ⅱ. Extended daytime effects of ClNO2 on urban winter air quality 6
Abstract 6
2.1. Introduction 6
2.2. Method 9
2.2.1. Measurement site 9
2.2.2. Instrumentation and data 10
2.2.3. Box model 12
2.3. Result and discussion 13
2.3.1. Overview of the campaign 13
2.3.2. Possible mechanisms contributing daytime ClNO2 16
2.3.3. Impacts of daytime ClNO2 on atmospheric oxidation 20
2.3.3.1. Production of Cl radical 20
2.3.3.2. Contribution to radical and O3 formation 20
2.4. Conclusions 26
2.5. Supplementary 27
Text S2.1. Identification and quantification of species measured by Q-CIMS 27
Text S2.2. Estimation of P(O3) and P(ROx) 28
Ⅲ. Examining driving factors of wintertime ClNO2 and its chemical regimes 40
Abstract 40
3.1. Introduction 40
3.2. Materials and method 43
3.2.1. Field observation and data collection 43
3.2.2. Machine learning model 44
3.3. Result and discussion 46
iii
3.3.1. Overview of measurements 46
3.3.2. Contribution of meteorological and chemical parameters 50
3.3.3. Chemical regimes in ClNO2 concentrations 56
3.4. Implications: Regime-specific control policy 58
3.5. Conclusions 59
3.6. Supplementary 60
Text S3.1. Gaussian Progress Regression model construction. 60
Text S3.2. Principle of Shapley additive explanation analysis 61
Ⅳ. Assessing nocturnal ClNO2 production rates in various environments with a new
analytical model 67
Abstract 67
4.1. Introduction 67
4.2. Method 69
4.2.1. Derivation of P(ClNO2) with analytical model 69
4.2.2. Field observations for model evaluation 70
4.3. Result 72
4.3.1. Observations of ClNO2 in various environments 72
4.3.2. Validation of analytical model for P(ClNO2) 75
4.3.3. Implications: Diagnosis tool for chemical regimes of P(ClNO2) 79
4.4. Conclusions 82
4.5. Supplementary 83
Text S4.1. Derivation of (ClNO2) and (N2O5) for Gwangju 2022 campaign 83
Text S4.2. Overview of measurement sites and instrumentation except Gwangju 2022
campaign 85
V. Development of a broadband cavity-enhanced absorption spectrometer for ambient NO 3
radical measurement 92
Abstract 92
5.1. Introduction 93
5.2. Instrumental setup 95
5.2.1. Optical layout 96
5.2.2. Flow and data acquisition system 97
5.3. Characterization 98
5.3.1. Determination of cavity parameters 98
5.3.1.1. Mirror reflectivity, () 98
5.3.1.2. Effective cavity length, 100
5.3.2. Retrieval of number density 101
5.3.2.1. Absorption cross-section, 101
5.3.2.2. Spectral fitting. 103
5.3.3. NO3 wall loss evaluation 104
5.3.3.1. NO3 generation 104
5.3.3.2. NO3 transmission efficiency, 3 105
5.3.4. Linearity tests 107
5.3.5. Precision and accuracy 109
5.4. Field deployment 112
5.5. Conclusions. 115
5.6. Supplementary 116
Ⅵ. Conclusions 117
6.1. Summary of this work 117
6.2. Recommendations for future work 118
References 121
Curriculum Vitae 15
Quasi-ordered plasmonic metasurfaces for optical security
No full textInspired by nature’s quasi-ordered structural colors, we demonstrate plasmonic metasurfaces that simultaneously produce vivid, stable coloration with unclonable optical fingerprints. This bioinspired approach bridges structural coloration and photonic security, offering a new pathway for anti-counterfeiting and optical identification technologies
The Effects of Garlic mustard Invasions on Soil Microbiome
No full textPlants influence soil biotic and abiotic properties, including microbial communities and nutrient cycling, affecting plant growth and reproduction. This process, known as plant-soil feedback, plays a key role in plant invasion. To investigate how they alter soil microbiome, we analyzed 80 soil samples collected in 2024 from Samcheok, Suwon, and Incheon, South Korea. Bacterial communities were assessed using full-length 16S sequencing, while fungal communities were analyzed through Illumina sequencing of the ITS2 region. Alpha diversity of bacteria was lower in invaded areas. In fungi, patterns varied by site: diversity increased in IC and SC but decreased in SW following invasion. Beta diversity also differed significantly between invaded and non-invaded areas. Differential abundance analysis identified shifts in key taxa. Among bacteria, three bacterial species increased in invaded areas, while one decreased. In fungal communities, eight species increased, whereas five species declined. Functional analysis using FAPROTAX revealed an increase in nitrite respiration, while analysis using FUNGuild showed that pathotroph-saprotroph function was more enriched in invaded areas. Our findings demonstrate that garlic mustard invasion alters microbial community composition and their functional roles, affecting soil ecosystem dynamics. These results provide insights into the mechanisms underlying garlic mustard’s invasion success