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Efficient simulation methodology for locally deformed cylindrical semiconductor devices
No full textNAND flash memory, a type of non-volatile memory, is widely used as a data storage device. In response to the demands of various applications such as smartphones, tablets, solid-state drives (SSDs), servers, and game consoles, three-dimensional (3D) architectures have been adopted instead of traditional two-dimensional (2D) structures to achieve high capacity and low cost, employing vertically stacked wordlines. However, limitations in etching technology during the manufacturing process have been reported to cause structural defects, such as tapering of the channel hole radius or the formation of polyhedral cross-sections. These structural defects negatively affect the electrical performance of memory cells, leading to performance variation, which has become a critical issue. Therefore, understanding how these structural defects impact memory performance and evaluating the resulting changes in electrical characteristics is essential. In this process, technology computer-aided design (TCAD) simulators serve as valuable tools to analyze and compare the electrical characteristics of ideal memory cells with those affected by structural variations.
3D NAND flash memory utilizes a gate-all-around (GAA) structure, and in such cylindrical configurations, efficient simulations can be performed using 2D meshes under axisymmetric conditions. However, when structural deformations break this symmetry, 3D meshes must be employed, significantly increasing the computational time required to solve the governing equations. Particularly, when structural deformation occurs only in specific regions or individual cells within the memory string, modeling the entire structure in 3D is inefficient and leads to an excessive use of computational resources.
In this dissertation, a hybrid 2D/3D method is proposed to efficiently simulate cylindrical devices with localized structural deformations, and a C++-based device simulator was developed. The hybrid 2D/3D mesh combines the advantages of both 2D and 3D meshes, overcoming the limitations of conventional approaches that rely on a single structure file, thereby enabling more efficient simulations. Simulations were conducted by applying different mesh types to the same cylindrical structure, and the accuracy and efficiency of the simulation results were compared and analyzed based on the mesh type. Additionally, this method was applied to the 3D NAND flash memory structure to effectively analyze how complex structural deformations in the channel hole impact the threshold voltage before and after programming operations.|비휘발성 메모리의 한 종류인 낸드 플래시 메모리는 데이터 저장 장치로 널리 사용되고 있다. 스마트폰, 태블릿, SSD, 서버, 게임 콘솔 등 다양한 응용 분야의 요구에 따라, 고용량과 저비용 메모리를 실현하기 위해 기존 2D 구조 대신 3D 구조가 도입되었으며, 수직 방향으로 워드라인을 적층하는 방식이 채택되었다. 그러나 제조 공정 중 에칭 기술의 한계로 인해 채널 홀의 반경이 변화하는 테이퍼링 현상이나 다면체 단면 형성 등 구조적 결함이 발생하는 것으로 알려져 있다. 이러한 결함은 메모리 셀의 전기적 성능에 영향을 미쳐 성능 산포를 초래하는 주요 원인이 된다. 따라서 이러한 구조적 결함이 메모리 성능에 미치는 영향을 규명하고, 전기적 특성 변화를 평가하는 것이 매우 중요하다. 이 과정에서 TCAD(Technology Computer-Aided Design) 시뮬레이터는 이상적인 메모리 셀과 비교하여 전기적 특성 변화를 분석하고 성능에 미치는 영향을 평가하는 데 매우 유용한 도구로 활용될 수 있다.
3D 낸드 플래시 메모리는 게이트-올-어라운드(Gate-All-Around) 구조를 가지고 있으며, 이러한 원통형 구조에서는 2차원 메쉬와 축대칭 조건을 적용해 효율적인 시뮬레이션을 수행할 수 있다. 그러나 축대칭이 깨지는 구조적 변형이 발생한 경우, 3차원 메쉬를 사용해야 하며, 이로 인해 지배 방정식을 풀고 해를 구하는 수치해석 과정에서 계산 시간이 크게 증가하는 문제가 발생한다. 특히 메모리 스트링 내 일부 영역 또는 특정 셀에서만 구조 변형이 발생하는 경우, 전체 구조를 3차원으로 모델링하여 시뮬레이션하는 것은 비효율적이며 과도한 계산 자원의 낭비를 초래할 수 있다.
본 학위 논문에서는 국소적 변형을 가진 원통형 소자의 시뮬레이션을 효율적으로 수행할 수 있는 하이브리드 2D/3D 방법을 제안하고, 이를 구현한 C++ 기반 소자 시뮬레이터를 개발하였다. 하이브리드 2D/3D 메쉬는 2차원 메쉬와 3차원 메쉬의 장점을 결합하여, 하나의 구조 파일만 사용하는 기존 방식의 한계를 극복하고 더욱 효율적인 시뮬레이션을 가능하게 한다. 동일한 원통형 구조에 서로 다른 차원의 메쉬를 적용해 시뮬레이션을 수행하고, 메쉬 유형에 따른 시뮬레이션 결과의 정확성과 효율성을 비교 분석하였다. 또한 3D 낸드 플래시 메모리 구조에 적용하여, 채널 홀의 복합적인 구조 변형이 프로그램 동작 전후 문턱 전압에 미치는 영향을 효과적으로 분석하였다.Docto
Development of a T Cell-Derived Immunological Synaptosome-Based Flt3L Delivery System and Its Role in Dendritic Cell Differentiation
No full textFlt3L is a key growth factor that promotes cDC1 differentiation essential for CD8⁺ T cell–mediated antitumor immunity. However, recombinant Flt3L (rmFlt3L) has limited clinical use due to its short half-life and off-target effects. This study developed a novel platform by fusing Flt3L to VSTM5 on CD4⁺ T cells, which release Flt3L-containing immunological synaptosomes (FL-TIS) upon TCR stimulation. FL-TIS retains membrane- bound Flt3L for targeted delivery to antigen-presenting cells. In vitro, FL-TIS more effectively enhanced cDC1 differentiation and myeloid cell proliferation. Thus, FL-TIS offers a promising cytokine delivery system for immunotherapy.|Engineered Immunological Synaptosome(EIS)는 T 세포의 미세융모에서 유래된 세포외소포로, 항원제시세포(APC)와 T 세포 사이에서 형성된 면역시냅스에서 T세포의 막이 떨어져나가면서 생성되고 항원제시세포에 선택적으로 결합하여 면역 정보를 전달한다. 본 연구에서는 미세융모에 특이적으로 분포하는 막관통 단백질 VSTM5에 Flt3L을 융합한 벡터를 제작해서 CD4⁺ T 세포를 형질전환시키고 강한 TCR 자극을 줘서 Flt3L를 발현하는 EIS(FL-TIS)를 제작하였다. 이 FL-TIS는 골수유래 전구세포의 conventional dendritic cell 1 (cDC1) 으로의 분화와 생존을 유지시켜 FL-TIS가 발현하는 Flt3L의 생물학적 기능이 유지됨을 확인했다. 이러한 결과는 EIS 기반의 사이토카인 전달 플랫폼이 높은 선택성과 효율성을 갖춘 새로운 면역치료 전략이 될 수 있음을 시사한다.MasterABSTRACT i
CONTENTS ii
LIST OF FIGURES iii
1. Introduction 1
2. Materials and methods 3
2.1. Reagents and antibodies 3
2.2. Cells 3
2.3. Animals 4
2.4. Cell transfection and retroviral infection 4
2.5. TISs isolation and purification 5
2.6. Western blot analysis 5
2.7. Confocal microscopy 6
2.8. ELISA 6
2.9. Flow cytometry analysis 6
2.10. Statistics 7
3. Results 8
3.1. Structure of V5G vector construct and transfection to plat E cell 8
3.2. Flt3L is expressed in engineered CD4 T cells and selectively delivered via
TISs 9
3.3. Flt3L-TIS promotes conventional dendritic cell 1 subtype (cDC1) differentiation
in vitro 10
4. Discussion 18
5. Abstract in Korean (국문요약) 20
6. References 2
Emerging trans-Eurasian heatwave-drought train in a warming climate
No full textSince the late 20th century, an emerging atmospheric teleconnection pattern, the trans-Eurasian heatwave-drought train, has intensified remarkably during summer, correlating with a surge in concurrent heatwave-drought events from Eastern Europe to East Asia. Tree-ring proxies, spanning three centuries, reveal that the recent intensity of this pattern is unprecedented in the historical records. In contrast, the circumglobal teleconnection, which historically dominated the continental-scale Eurasian heatwave occurrences, has shown no discernible trend amid global warming. Consequently, this emerging pattern signifies a radical shift in Eurasian heatwave-drought climatologies. The mechanism involves Rossby wave propagation linked to warming sea surface temperatures in the Northwestern Atlantic and enhanced Sahel precipitation, both amplified recently by overlapping effects of anthropogenic warming and natural variability. Land-atmosphere interactions driven by soil moisture deficits further intensified the pattern regionally. Climate models predict that anthropogenic forcings will continue to strengthen the pattern throughout this century.TRUEsciescopu
The electrochemical subsurface treatment of Ni-based catalytic materials for efficient alkaline water electrolysis Gwangju Institute of Science and Technology School of Materials Science and Engineering Seunghyun Jo
No full textDue to the high cost of noble metal catalysts such as platinum (Pt) and iridium (Ir), which are commonly used in catalytic material for water electrolysis, the competitiveness of green hydrogen has been evaluated as lacking. In response, nickel-based compounds have received significant attention as catalyst for hydrogen evolution reactions (HER) and oxygen evolution reactions (OER), owing to their low cost and relatively high reactivity. However, homogeneous nickel (Ni) or nickel oxide (NiO) face several challenges in competing with noble metal catalysts. First, as a hydrogen evolution catalyst, Ni shows lower performance compared to the noble metal catalyst, Pt. Then, as an oxygen evolution catalyst, Ni oxidizes to nickel oxyhydroxide (NiOOH) via NiO, but the balance between the reaction steps is disrupted, resulting in lower performance compared to the noble metal catalyst IrO2. Additionally, Ni suffers from rapid corrosion under OER conditions, leading to shorter lifespans. To address these issues, various Ni-based compound catalysts are being developed, but to date, the gap between the theoretically optimized performance and the practical challenges in synthesis and application has prevented commercialization. In this point, electrochemical surface modification techniques offer a potential solution to solve these problems. Because the catalytic reactions occur on the electrochemical active surface area (ECSA) of the catalyst, the surface properties of the material critically affect the catalytic performance. In this contents, by using electrochemical methods to modify the catalyst surface, it is possible to minimize side effects by equalizing the reactive surface area with the modified area, and providing engineering advantages for practical applications such as water electrolysis single cell. In this thesis, I analyze the mechanisms by which Ni-based compounds enhance catalytic performance and suggest two electrochemical surface modification methods to solve the identified research gap.
At first, it involves doping bismuth (Bi) additive to NiO catalysts and analyzing its effects on the activity and stability of alkaline HER and OER. Because Bi has a higher electronegativity than Ni, Bi doping is able to control the electronic structure of Ni by transferring electrons. Additionally, Bi is a suitable metal for catalysis due to reversible redox reactions under alkaline hydrogen and oxygen evolution conditions. Through chemical and electrochemical analysis, this study aims to enhance the hydrogen and oxygen evolution rates of NiO catalysts via Bi doping and to use computational calculations to investigate how Bi doping affects the mechanisms of each reaction.
Then, the first approach involves optimizing the hydrogen evolution performance of Ni-P catalysts through electrochemical surface engineering to create a P-rich surface. By analyzing the influence of additives, the study identifies the optimal composition between Ni and P. Then, by adjusting the composition on the electrochemical active surface through electrochemical surface modification, it optimizes the activity and durability as basis on each mechanism of HER in acidic and alkaline media.
Finally, the second approach introduces an in-situ electrochemical surface modification to control the surface crystallinity of NiFe-LDH catalyst, accelerating the oxygen evolution rate in alkaline media. NiFe-LDH catalyst possess a 2D layered structure, where the high resistance encountered by OH- ions moving into the narrow 2D layers and contributed to performance degradation. The in-situ surface modification reduces the pathway resistance for OH- ions, thereby increasing the oxygen evolution rate and enhancing the durability of the catalyst.DoctorAbstract i
Contents iii
List of Tables v
List of Figures vi
Ⅰ. Introduction 1
I.1. Hydrogen fuel 1
I.2. Water electrolysis 3
I.3. Mechanism of hydrogen evolution reaction (HER) and electrocatalysts 5
I.4. Mechanism of oxygen evolution reaction (OER) and electrocatalysts 9
I.5. Electrochemical surface engineering 11
I.6. References 15
Ⅱ. Theoretical Background 25
II.1. Computational investigation of theoretical properties of electrocatalysts 25
II.2. Electrochemically evaluating components for electrocatalysts 28
II.3. References 31
Ⅲ. Experiments 33
III.1. Preparation of Bi doped NiO electrocatalyst (for section IV) 33
III.2. Preparation of P-rich Ni-P electrocatalyst (for section V) 34
III.3. Preparation of NiFe-LDH and in-situ electrochemical modification (for section VI) 35
III.4. Computational methods 36
III.6. Electrochemical measurements 38
III.7. Alkaline water electrolysis single-cell test (for section IV) 39
III.8. References 40
IV. The effect of Bi doping on Ni-O electrocatalysts for efficient hydrogen/oxygen
evolution reaction in alkaline media 42
IV.1. Background 42
IV.2. Characterizations 43
IV.3. Catalytic performances of hydrogen and oxygen evolution reaction 48
IV.4. Density function theory calculations for hydrogen and oxygen evolution reaction 53
IV.5. Single-cell performance for alkaline water electrolysis 56
IV.6. References 57
V. Reconstruction of a surficial P-rich layer on Ni-P electrocatalysts for efficient
hydrogen evolution applicable in acidic and alkaline media 59
V.1. Background 59
V.2. Design of the surface treatment method for high-performance Ni-P/CFP 62
V.3. Microstructure and surface characterization of Ni-P/CFP 64
V.4. Electrochemical characterization of CV dealloyed Ni-P/CFP for the HER in acidic
media 67
V.5. Electrocatalytic performance of CV dealloyed Ni-P/CFP for the HER in alkaline
media 73
V.6. Density functional theory (DFT) calculations 75
V.7. References 78
VI. In-situ electrochemical modification of crystallinity of NiFe-LDH for efficient
oxygen evolution reaction in alkaline media 83
VI.1. Background 83
VI.2. Electrochemical characterization of NiFe-LDH catalysts 86
VI.3. Chemical characterization of NiFe-LDH catalysts 92
VI.4. Durability of NiFe-LDH catalysts for OER 96
VI.5. References 100
ⅤII. Overall Conclusion 104
Acknowledgement 11
Switchable Multi-wavelength Coaxial Optics for Active Protection Systems
No full text본 논문은 능동방어 시스템에서 다중 파장 레이저를 단일 광축에 정밀 정렬하기 위한 구조적 정렬 광학계를 제안한다. 본 시스템은 다중 파장 간의 정렬을 정밀하게 수행할 수 있을 뿐 아니라, 분리형 정렬 경로 구조를 통해 실제 운용 경로상의 정렬 상태를 사전에 확인할 수 있도록 설계되었다. 정렬 기준은 785 nm 기준 레이저를 SWIR (short-wave infrared) 영상 중심에 정렬한 후, 근거리장/원거리장 위치에 배치된 PSD (position-sensitive detector)를 이용하여 기준 축을 정밀하게 설정한다. 이후 각 파장 레이저는 피코모터 기반 미러 조정을 통해 기준 축에 순차적으로 정렬된다. 실험 결과, 파장 간 중심 오차는 15 mrad 이내였으며, 피코모터 기반 미세 조정 장치가 장기 운용 시에도 정렬 안정성을 유지하는 데 효과적임을 확인하였다. 제안된 방식은 고정밀 조준형 광학 시스템에서 요구되는 정렬 정확도와 운용 효율성을 동시에 충족하며, 다중 파장 기반 비살상 무력화 시스템 등에 효과적으로 적용될 수 있다.TRUEkc
Data-augmented turbulence modeling for separated compressible flow around axisymmetric bodies
No full textFlow around an axisymmetric body at high speeds involves flow separation coupled with compressibility effects, which imposes challenges for conventional Reynolds-averaged Navier-Stokes (RANS) turbulence models. The field inversion and machine learning (FIML) approach is employed to improve a RANS model. This study introduces novel flow features to incorporate compressible and rotational effects in a data-augmented approach. The proposed flow features are based on physics-and knowledge-driven model corrections, considering practices recommended for modeling turbulent flow. The current trained model with proposed flow features covers a wide range of the Mach number, including subsonic, transonic, and supersonic conditions. The eddy viscosity in the separated region is adequately reduced in the trained RANS model, which improves the predictive capability of separated compressible flow around axisymmetric bodies. The trained RANS model with two-dimensional flow data is also validated with a three-dimensional axisymmetric body at non-zero angles of attack. The improvement in modeling separated compressible flow is discussed further with conventional RANS corrections.FALSEsciescopu
A Single-step Platinum Nanoparticle-Enhanced Lateral Flow Immunoassay Platform for Rapid Detection of Influenza A Virus
No full textLateral flow immunoassays (LFIAs) are widely used point-of-care (POC) diagnostic tools, but their limited sensitivity can hinder reliable diagnoses. To address this limitation, we developed a novel POC diagnostic platform for the highly sensitive detection of influenza A virus (IAV). This developed platform integrates platinum nanoparticle–catalyzed 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation for reagent-free, single-step signal amplification with smartphone-based image acquisition and quantitative analysis. This combination of catalytic enhancement and digital interpretation enables rapid, objective, and quantitative diagnostic evaluation, offering improved performance over conventional LFIAs. Upon sample application, the sample flows to complete the immunoreaction at the test line, followed by a chromatographically delayed acidic migration that rehydrates the TMB and delivers it to the captured platinum nanoparticles for signal amplification. This reagent-free, timed enhancement results in approximately 100-fold visual signal amplification compared to unenhanced detection, without the need for additional reagents. Additionally, a custom-developed smartphone application automates image acquisition and quantifies intensity ratios to provide the final diagnosis. The platform achieves a limit of detection of 11.6 pg/mL IAV nucleoprotein within 15 min, offering a 1000-fold increase in sensitivity over traditional LFIAs. In clinical trials, it demonstrated excellent performance, with 96.8% sensitivity and 98.4% specificity compared to RT-PCR. The platform also exhibited semiquantitative capability, with a strong inverse correlation (R2= 0.832) between RT-PCR Ct values and intensity ratios. This integrated system provides a rapid, low-cost, and user-friendly solution for accurate viral diagnostics. © 2025 American Chemical SocietyFALSEscopu
Beyond Sound: AI-based Multimodal Music Systems for d/Deaf and Hard-of-Hearing Individuals from Appreciation to Creation and Therapy
No full textFrom an inclusive art perspective, artistic expression should not be confined to specific senses or restricted to particular groups. Emerging technologies, such as Generative AI, expand creative possibilities by engaging multiple senses. This advancement is particularly significant for individuals with disabilities, as it challenges the notion of “limited senses” and instead highlights their enhanced abilities in other sensory domains, offering new opportunities for artistic expression.
As a multimodal art form, music integrates images, video, and text, making it inherently accessible beyond auditory perception. However, deaf and hard-of-hearing (DHH) individuals often encounter barriers to musical engagement due to limited access to sound. To address this, research has primarily focused on music-sensory substitution systems that translate musical elements into visual and tactile feedback. While these approaches help develop musical skills such as sound perception, instrument playing, and singing, they often fail to capture music's deeper artistic and emotional value.
This study aims to support active and independent musical engagement for DHH individuals by integrating music-sensory substitution systems with Generative AI. This research highlights the intrinsic value of music for DHH individuals and aims to develop a technology-based inclusive music accessibility system. Rather than focusing solely on skill acquisition, it seeks to foster deeper experiences such as pleasure, self-awareness, and self-reflection. To achieve this, four key research objectives will be pursued: (1) conceptualizing rich emotional experiences in music through alternative sensory modalities, (2) developing an interactive music-making system based on song signing, (3) implementing an AI-driven autonomous music composition tool, and (4) designing and validating an LLM-based therapeutic music system for self-reflection.
This study holds significance in three key aspects. First, it promotes inclusivity by recognizing DHH individuals as active participants in music culture. Second, it introduces a new multimodal paradigm for musical engagement that extends beyond the DHH community to benefit children, the elderly, and neurodivergent individuals. Third, it fosters empowerment by enhancing creative expression and self-confidence through technology, overcoming traditional limitations associated with hearing impairments. By emphasizing the need for continued attention to marginalized groups in technological advancements, this research contributes to more inclusive and equitable musical experiences. Ultimately, it envisions a society where technological innovations bridge gaps and enrich artistic expression for all, regardless of sensory abilities.DoctorI. INTRODUCTION 1
1.1. Background and Motivation 1
1.2. Thesis Overview 2
1.3. Contribution ３
II. Related Work ３
2.1. Values of Music ３
2.2. Music and Deaf and Hard-of-Hearing ４
2.3. Music Assistive Technology ６
2.4. Definition of d/Deaf and Hard-of-Hearing ７
III. RESEARCH QUESTIONS ８
Ⅳ. RESEARCH METHODOLOGY ９
4.1. Overall Study Process ９
4.2. Data Gathering and Analysis ９
V. RQ1. Value and Strategy of Improving Engagement of Music Experience 10
5.1. Related Works 10
5.1.1. Passive musical activities through a music-sensory substitution system for d/DHH 10
5.1.2. Improving engagement of music activities for d/DHH 11
5.2. Preliminary Study: Understanding the Musical Experience of d/DHH 13
5.2.1. Methods 13
5.2.2. Findings 14
5.3. Study 1. Improving Engagement in Music Appreciation 17
5.3.1. Design of cross-modal conceptualization for music appreciation 17
5.3.2. User study 20
5.3.2. Findings 22
5.4. Study 2. Improving Engagement in Music-making 17
5.4.1. Design of a multimodal synthesizer for creating song signing 25
5.4.2. User study 28
5.4.3. Findings. 29
5.5. Summary (RQ1) 32
VI. RQ2. Mental Health Value of Autonomous Music Creation 33
6.1. Related Works 33
6.1.1. The mental well-being music creation 33
6.1.2. AI for music creation 34
6.1.3. AI for psychotherapy 35
6.2. Preliminary Study: Exploring Music Creation Possibility for d/DHH 37
6.2.1. Video prototype 37
6.2.2. Interviews 38
6.2.3. Findings 39
6.3. Overall Study Process 43
6.4. Study 3. Supporting d/DHH Individuals' Independence through Autonomous Music-making 44
6.4.1. Design of music-making assistive tool based on music GenAI 44
6.4.2. Music-making study 49
6.4.3. Findings 50
6.5. Study 4. Supporting d/DHH Individuals' Mental Well-being through Autonomous Music-making 59
6.5.1. Design workshop with therapists 59
6.5.2. Implementation of music psychotherapy assistive tool based on LLM 64
6.5.3. Usage study 68
6.5.3. Findings 72
6.6. Summary (RQ2) 81
VII. Discussion 82
7.1. Collaboration with Mixed-hearing Group 82
7.2. Supporting Creative Autonomy through Multimodal Music 83
7.3. Inclusive Generative AI Technology 84
7.4. Accessibility of Music Experience 85
7.5. Limitation and Future work 85
VIII. Conclusion 86
References 8
Investigation of DC and AC Characteristics in Gate-All-Around Field-Effect Transistor Using the Non-equilibrium Green’s Function Approach
No full textElectron transport simulation plays a pivotal role in understanding and predicting the performance of electronic devices. In both industry and academia, Technology Computer-Aided Design (TCAD) is commonly used for device simulation. Additionally, the Multi-Subband Boltzmann Transport Equation (MSBTE) is often employed to incorporate physical aspects of electron transport. However, as device dimensions continue to scale down, quantum effects become increasingly significant. To address these quantum effects, quantum transport simulations have been widely adopted, with the Non-Equilibrium Green’s Function (NEGF) method serving as a standard approach. Over the years, NEGF has evolved to involve complex band structures, improve computational efficiency, and integrate various physical models. It is now widely used in electron transport simulations and frequently serves as a benchmark for validating other transport models. Despite its advancements, NEGF still faces several limitations. One such limitation is that it has traditionally been restricted to DC simulations, whereas TCAD and MSBTE are already capable of AC and transient analyses. AC simulation is particularly important for extracting parameters such as Y-parameters and cutoff frequency, and it also serves as a prerequisite for noise analysis. Another limitation is that NEGF does not deterministically account for the effect of surface roughness. This thesis aims to address these limitations. Chapter 1 provides a brief introduction to device simulation and the NEGF method. Chapter 2 introduces conventional DC NEGF simulation, outlining the governing equations and typical simulation procedure. Chapter 3 presents a fully coupled scheme in which the Poisson equation and NEGF are combined into a single system matrix and solved simultaneously. As a result, the number of iterations required for convergence can be reduced. Moreover, the proposed fully-coupled scheme provides the capability of AC NEGF simulation. In chapter 4, the implementation of AC NEGF is described, extending NEGF’s capabilities beyond DC analysis. The accuracy of the AC NEGF implementation is validated, and current conservation is examined. Subsequently, AC simulations are performed to extract Y-parameters and cutoff frequencies. Plasma instabilities induced by ungated regions are investigated using the AC NEGF approach. In addition, the AC NEGF simulation is extended to include electron-phonon scattering, and the corresponding results were analyzed. Chapter 5 presents NEGF simulations incorporating the mode coupling effect which may be induced by the surface roughness. Mode coupling is represented as a scattering process via this mathematically derived model. The derivation of the proposed geometric scattering model is introduced. The proposed model is validated through the simulation and discussion is provided.Doctor1. Introduction 1
1.1 Device development 1
1.2 Transport simulation 3
1.2.1 Technology Computer-Aided Design 3
1.2.2 Non-equilibrium Green’s function 4
1.3 Organization 6
2. Conventional DC NEGF Simulation Framework 8
2.1 Poisson equation 9
2.2 Schrödinger equation 10
2.3 NEGF framework 11
2.3.1 Real-space NEGF 12
2.3.2 Mode-space NEGF 16
2.4 NEGF simulation procedure 20
2.5 DC NEGF simulation result 23
2.6 Conclusion 25
3. Fully-Coupled Scheme for NEGF Simulation 26
3.1 Fully-coupled scheme 27
3.2 Simulation result 32
3.3 Conclusion 41
4. AC NEGF simulation 42
4.1 AC NEGF approach 43
4.1.1 Relations for AC NEGF simulation 44
4.1.2 Solution procedure for AC NEGF simulation 48
4.1.3 Response calculation 50
4.1.4 Simulation results and discussion 53
4.2 AC NEGF including electron-phonon scattering 64
4.2.1 Methodology 64
4.2.2 Implementaion 67
4.2.3 Simulation result 71
4.3 Conclusion 74
5. Describing Geometric Fluctuation as a Scattering 76
5.1 Derivation 77
5.2 Approximated form 81
5.3 Simulation procedure and result 82
5.4 Discussion 86
Summary 88
References 91
Acknowledgements 10
Comparative Evaluation of Relaxation-Based Bio-sensing Performance of Magnetic Nanoparticles Using Magnetic Particle Spectroscopy
No full textMagnetic Particle Spectroscopy (MPS) is a highly sensitive, label-free technique for detecting biomolecular interactions through the nonlinear magnetization of magnetic nanoparticles (MNPs). This study presents a comparative performance evaluation of four commercial carboxyl-functionalized MNPs: Resovist®, Perimag®, Synomag®, and SHP-30 (Ocean NanoTech), to assess their biosensing suitability using MPS. Measurements at 5, 15, and 25 kHz in water, glycerol, and agarose characterized medium- and frequency-dependent relaxation: SHP-30 exhibited predominantly Brownian relaxation with the highest sensitivity to hydrodynamic size changes; Perimag® showed slower Brownian behavior with reduced sensitivity; Resovist® was predominantly Néel-dominated; and Synomag® displayed mixed relaxation. For biosensing efficiency, all four MNPs were conjugated with H1N1 hemagglutinin protein via EDC–NHS chemistry, and bio-conjugation was confirmed by FT-IR (amide I/II) and DLS (increased hydrodynamic size). ICP-MS quantified the retained iron content after conjugation and washing, and all samples were normalized to the same iron mass for MPS measurement. Frequency-tuned MPS measurements identified that SHP-30 exhibited significantly greater signal suppression at low frequencies (∼7.74 kHz) upon protein binding, enabling protein detection limit down to 10 nM. Collectively, these findings establish SHP-30 as a highly sensitive and efficient candidate for biomarker-conjugated MPS diagnostics, with potential utility in infectious disease detection and point-of-care applications. © 2002-2011 IEEE.FALSEsciescopu