<p>Transition metal dichalcogenides (TMDs) have attracted significant attention in recent years with their immense potential to revolutionize optoelectronics and electrochemical energy applications. However, several challenges have prevented their practical use, including fabrication difficulties, incompatibility with conventional doping techniques, and unwanted environmental effects. This thesis aims to address the issues by introducing novel strategies for transforming TMDs into organic-integrated hybrid structures. Furthermore, this study focuses on gaining a fundamental understanding and a tunability of the unique physical properties of TMDs. Finally, to unlock their full potential, this thesis explores synergetic effects among the hybrid components for the development of advanced optoelectronics and energy devices. </p> <p><br></p> <p>By combining atomically thin TMDs with uniform organic layers, we have developed various two-dimensional (2D) hybrid junctions, including TMD/organic, TMD/TMD/organic, and TMD/organic/TMD. The TMD/organic hybrids are designed for type-II energy band alignments at the heterointerface and exhibit significantly improved (photo)conductivity and uniform photoresponse compared to pristine TMDs. The optoelectronic characteristics vary as a function of the layer number of TMDs, one of the unique features of ultrathin materials. We also find that integrating organic layers can tailor the charge density and polarity of TMD flakes, thus enabling controllable doping without damaging the crystallinity. </p> <p><br></p> <p>The hybrid approach not only modulates the properties of individual TMD layers but also offers an opportunity to study unique phenomena of 2D heterostructures such as interlayer excitons (XIs). XIs are spatially separated bound states of an electron and a hole in TMD/TMD heterolayers. We prepared various TMD/TMD/organic hybrid heterostructures with distinct energy band alignments and demonstrated a selective modulation of XI emission. The photoluminescence from the radiative recombination of XIs can be preserved, quenched, or modulated based on the band alignments. Furthermore, we fabricated organic-layer-inserted heterolayers (TMD/organic/TMD) and investigated the environmental effects on XIs. The organic layers tailor the dielectric screening within XIs and the dipolar interaction among XIs, thus regulating the energy states of XIs.</p> <p> </p> <p>In addition to the rich potential in optoelectronics, the hybrid strategies are advantageous to improve electrochemical energy storage. We constructed hybrid composites from core carbon nanotubes, intermediate metal-organic frameworks (MOFs), and outer TMD layers for supercapacitor electrodes. The 3D hierarchical composites aim to achieve synergetic effects from the components and offer high energy density while maintaining excellent power density and durability. Percolated nanotube networks are highly conductive, MOFs ensure a fast ion diffusivity, and TMD offers a large ion capacity. We engineered the TMD morphologies via topochemical synthesis and determined the optimal structure maximizing faradaic-reactive surface areas for improved ion accumulation and redox energy storage. We found that the hybrid composite of a flower-like TMD structure interwoven with carbon networks exhibits an unprecedentedly high energy density of over 80 Wh/kg, superior to conventional supercapacitors. </p> <p><br></p> <p>In summary, this thesis presents powerful strategies for engineering atomically thin TMDs and critical insights on relevant physics which may not be accessible otherwise. Given the extensive library of organic molecules, the hybrid approach may provide a versatile platform to study 2D materials and open new opportunities. The findings could serve as the foundation for the development of novel optoelectronic and energy storage applications.</p>

Graphene features a unique combination of exceptional properties and has emerged as one of the most promising nanomaterials for a variety of applications. The ability to structurally modify graphene with nanoscale precision enables the properties to be further extended. By introducing nanopores in the graphene lattice, nanoporous graphene can be used in high-performance electronic devices or as selective membranes for efficient molecular filtering. Although methods for deterministic nanopatterning already exists, key for the implementation of nanoporous graphene is the development of a scalable and customisable method of patterning graphene that does not require any lithographic mask that is introducing defects. In this project, a novel approach using a nanoporous mask and a broad beam of 20 keV Ar ions has been investigated. Masks with 60-600 nm circular pores have been fabricated, and by irradiating suspended graphene membranes grown by chemical vapor deposition (CVD) through the mask, nanoporous graphene has been deterministically generated. The masks are fabricated using electron beam lithography, and the pattern is highly customisable regarding pore size, pore distribution and areal coverage. In addition to perforating the graphene, the ion beam is also observed to significantly reduce the level of contamination on the graphene membrane. The proposed mechanism is the combination of electronic  sputtering of surface contaminants and the random diffusion that follows, with a low nuclear sputtering yield and to-site pinning of contaminants. An extension of this study could include a more comprehensive characterization of the nanoporous graphene obtained as well as further studies on the dependency of beam parameters.

Nano and nanostructured materials offer unique physical and chemical properties that differ considerably from their bulk counterparts. For decades, due to their fascinating properties, they have been extensively explored and found to be beneficial in numerous applications. These materials are key components in many cutting-edge optic and photonic technologies, including photovoltaics, waveguides and sensors. In this dissertation, the uses of nano and nanostructured materials for optical applications are investigated in the context of optical limiting, three dimensional displays, and optical sensing. Nanomaterials with nonlinear optical responses are promising candidates for self-activating optical limiters. In the first part of this study, optical limiting properties of unexplored nanomaterials are investigated. A photoacoustic detection technique is developed as an alternative characterization method for studying optical nonlinearities. This was done with an indigenously developed setup for measuring the photoacoustic signals generated from samples excited with a pulse laser. A theoretical model for understanding the experimental observations is presented. In addition, the advantages of this newly developed technique over the existing methods are demonstrated. Blending optical sensitizers with photoconducting polymers and chromophores results in a polymer composite that is able to record a light grating. This composite can be used as recording media in 3D holographic display technology. Here, 2D nano materials, like graphenes, are used as optical sensitizers to improve the response time of a photorefractive polymer. The addition of graphenes to a PATPD/ECZ/7-DCST composite results in a three-fold enhancement in response time and therefore faster recording speed of the medium. The faster build-up time is attributed to better charge generation and mobility due to the presence of graphenes in the composite. Lastly, a facile nanofabrication technique is developed to produce metallic nanostructures with a tunable plasmonic response. The enhancement of the light-matter interactions due to these nanostructures in sensing an analyte is demonstrated.

This thesis discusses the full scope of a project exploring the physics of hierarchical clusters of interacting nanomagnets. These clusters may be relevant for novel applications such as multilevel data storage devices. The work can be grouped into three main activities: micromagnetic simulation, fabrication and characterization of proof-ofconcept prototype devices, and efforts to scale down the structures by creating the hierarchical structures with the aid of diblock copolymer self assembly. Theoretical micromagnetic studies and simulations based on Landau-Lifshitz- Gilbert (LLG) equation were conducted on nanoscale single domain magnetic entities. For the simulated nanomagnet clusters with perpendicular uniaxial anisotropy, the simulation showed the switching field distributions, the stability of the magnetostatic states with distinctive total cluster perpendicular moments, and the stepwise magnetic switching curves. For simulated nanomagnet clusters with in-plane shape anisotropy, the simulation showed the stepwise switching behaviors governed by thermal agitation and cluster configurations. Proof-of-concept cluster devices with three interacting Co nanomagnets were fabricated by e-beam lithography (EBL) and pulse-reverse electrochemical deposition (PRECD). EBL patterning on a suspended 100 nm SiN membrane showed improved lateral lithography resolution to 30 nm. The Co nanomagnets deposited using the PRECD method showed perpendicular anisotropy. The switching experiments with external applied fields were able to switch the Co nanomagnets through the four magnetostatic states with distinctive total perpendicular cluster magnetization, and proved the feasibility of multilevel data storage devices based on the cluster concept. Shrinking the structures size was experimented by the aid of diblock copolymer. Thick poly(styrene)-b-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer templates aligned with external electrical field were used to fabricate long Ni/Fe magnetic nanowire array, dominant shape anisotropy was observed and compared to the result from previously reported Co nanowire array with strong crystalline anisotropy. Guided diblock copolymer poly(styrene)-b-poly(4-vinyl pyridine) (PS-b-P4VP) self assembly was performed to generate clustered microdomains. Direct e-beam patterning on PS-b-P4VP thin film showed precise and arbitrary patterning on the lateral ordering of the self assembly. Graphoepitaxy of self-assembled PS-b-P4VP copolymers on isolated SiN triangular plateaus successfully resulted in the exact clusters of three microdomains. Theoretical consideration and system modeling based on the micellar configuration of the microdomains were done, and the distribution of the cluster’s size and number of elements were explained qualitatively.

This thesis reports the fabrication of nanophotonic structures by using electron beam lithography and using pattern transfer via self assembly with the aid of block copolymers. A theoretical and experimental basis was developed for fabricating anti-reflective coatings using block-copolymer pattern transfer. Block-copolymers were also used to fabricate plasmonic pattern arrays which form gold dots on glass surface. Electron-beam lithography was utilized to fabricate holey plasmonic structures from gold and silver films. Electron-beam exposure was used in block-copolymer lithography in selected regions. The exposure effects were studied for both thin and thick block-copolymer films. Reactive and ion beam etching techniques were used and optimized to fabricate those structures. This research required a great deal of development of new fabrication methods and key information is included in the body of the thesis.

No description available.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24585号 / 工博第5091号 / 新制||工||1975(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 関 修平, 教授 梶 弘典, 教授 SIVANIAH Easan / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical technique that combines molecular specificity of vibrational fingerprints offered by Raman spectroscopy with single-molecule detection sensitivity from plasmonic hotspots of noble metal nanostructures. Label-free SERS has attracted tremendous interest in bioanalysis over the last two decades due to minimal sample preparation, non-invasive measurement without water background interference, and multiplexing capability from rich chemical information of narrow Raman bands. Nevertheless, significant challenges should be addressed to become a widely accepted technique in bio-related communities. In this dissertation, limitations from different aspects (performance, reliability, and analysis) are articulated with state-of-the-art, followed by how introduced works resolve them. For high SERS performance, SERS substrates consisting of vertically-stacked multiple metal-insulator-metal layers, named nanolaminate, were designed to simultaneously achieve high sensitivity and excellent uniformity, two previously deemed mutually exclusive properties. Two unique factors of nanolaminate SERS substrates were exploited for the improved reliability of label-free in situ classification using living cancer cells, including background refractive index (RI) insensitivity from 1.30 to 1.60, covering extracellular components, and 3D protruding nanostructures that can generate a tight nano-bio interface (e.g., hotspot-cell coupling). Discrete nanolamination by new nanofabrication additionally provides optical transparency, offering backside-excitation, thereby label-free glucose sensing on a skin-phantom model. Towards reliable quantitative SERS analysis, an electronic Raman scattering (ERS) calibration method was developed. ERS from metal is omnipresent in plasmonic constructs and experiences identical hotspot enhancements. Rigorous experimental results support that ERS can serve as internal standards for spatial and temporal calibration of SERS signals with significant potential for complex samples by overcoming intrinsic limitations of state-of-art Raman tags. ERS calibration was successfully applied to label-free living cell SERS datasets for classifying cancer subtypes and cellular drug responses. Furthermore, dual-recognition label-SERS with digital assay revealed improved accuracy in quantitative dopamine analysis. Artificial neural network-based advanced machine learning method was exploited to improve the interpretability of bioanalytical SERS for multiple living cell responses. Finally, this dissertation provides future perspectives with different aspects to design bio-interfaced SERS devices for clinical translation, followed by guidance for SERS to become a standard analytical method that can compete with or complement existing technologies. / Doctor of Philosophy / In photonics, metals were thought to be not very useful, except mirrors. However, at a length scale smaller than wavelength, it has been realized that metallic structures can provide unique ways of light manipulation. Maxwell's equations show that an interface between dielectric and metal can support surface plasmons, resulting in collective oscillations of electrons and light confinement. Surface-enhanced Raman spectroscopy (SERS) is a sensing technique that combines enhanced local fields arising from plasmon excitation with molecular fingerprint specificity of vibrational Raman spectroscopy. The million-fold enhancement of Raman signals at hotspots has driven an explosion of research, providing tons of publications over the last two decades with a broad spectrum of physical, chemical, and biological applications. Nevertheless, significant challenges should be addressed for SERS to become a widely accepted technique, especially in bio-related communities. In this dissertation, limitations from different aspects (performance, reliability, and analysis) are articulated with state-of-the-art, followed by how innovative strategies addressed them. Each chapter's unique approach consists of a combination of five aspects, including nanoplasmonics, nanofabrication, nano-bio interface, cancer biology, statistical machine learning. First, high-performance SERS substrates were designed to simultaneously achieve high sensitivity and excellent uniformity, two previously deemed mutually exclusive properties, by vertically stacking multiple metal-insulator-metal layers (i.e., nanolaminate). Their 3D protruding nanotopography and refractive-index-insensitive SERS response enabled label-free in situ classification of living cancer cells. Tweaked nanofabrication produced discrete nanolamination with optical transparency, enabling label-free glucose sensing on a skin phantom. Towards reliable quantitative SERS analysis, an electronic Raman scattering (ERS) calibration method was developed that can overcome the intrinsic limitations of Raman tags, and it was successfully applied to label-free living cell SERS datasets for classifying cancer subtypes and cellular drug responses. Furthermore, dual-recognition label-SERS with digital assay revealed improved accuracy in quantitative dopamine analysis. Advanced machine learning (artificial neural network) was exploited to improve the interpretability of SERS bioanalysis for multiple cellular drug responses. Finally, this dissertation provides future perspectives with different aspects, including SERS, biology, and statistics, for SERS to potentially become a standard analytical method that can compete with or complement existing technologies.

Monitoring biological systems is crucial in healthcare, driving the need for reliable and noninvasive solutions. The proliferation of unverified drugs in the market necessitates reliable methods for their detection and identification, especially amidst advancements in pharmaceuticals. Plasmonic biosensors emerge as a great platform for ultra-sensitive detection, identification, and manipulation of biomolecular systems. This dissertation report addresses the critical need for precise detection and monitoring of biomolecules and drugs, presenting innovative solutions through the design of a plasmonic biosensor to tackle challenges in sensitivity, selectivity, and label-free detection and identification. We introduce a robust and tunable, cavity-integrated plasmonic nanopatterned sensor that exhibits superchiral light in the infrared domain for ultrasensitive detection of chiral molecular concentrations and enantiomeric excesses. The multispectral capability of this system is further harnessed to generate unique chiral fingerprint-based barcodes for the identification of diverse chiral drugs and biomolecules. We further discuss and demonstrate results for a surface-modified plasmonic biosensor operating in the visible-near-infrared realm in detecting viral biomarkers and neurotransmitters directly from complex physiological environments. The system, on coupling with a microfluidic flow setup allows sensitive, selective and rapid detection without requiring complex pre-processing or sample preparation steps. We discuss additional applications of the unique plasmonic sensor, utilizing the property of tunable superchirality to create a dynamic chirality tracking system operating in the near infrared for real-time monitoring of protein dynamics. These techniques aim to revolutionize bio-detection, chiral differentiation, and sorting processes, having extensive applications in medical research and pharmaceutical industries.

<p dir="ltr">The rapid evolution of semiconductor technology, driven by the limitations of Moore's Law, necessitates innovative approaches to enhance device performance and miniaturization. This thesis explores the advancement of three-dimensional integrated circuits (3D-ICs) using flexible glass-based substrates, focusing on their application in extreme environments. Flexible glass emerges as a promising material for 3D-IC packaging due to its superior electrical insulation, thermal stability, chemical resistance, and mechanical strength. These properties are critical for maintaining device reliability and functionality under harsh conditions such as high temperatures, humidity, and radiation. Their unique properties make them particularly suited for applications in aerospace, military, and automotive industries, where electronics must endure severe operational environments. The research presented in this thesis provides a comprehensive examination of the processes involved in fabricating flexible glass-based 3D-ICs, detailing methodologies for integrating semiconductor components onto a flexible glass substrate using common platform technology (CPT). This approach ensures compatibility across diverse systems and enhances the scalability and cost-effectiveness of 3D-IC solutions. Experimental results indicate that 3D-ICs incorporating flexible glass substrates exhibit enhanced functionality and durability. This study underscores the transformative potential of flexible glass in revolutionizing the design and performance of future electronic systems, ensuring their operability and longevity in demanding settings. By addressing the challenges of traditional packaging materials, flexible glass represents a significant advancement in 3D-IC technology, promising to broaden the operational landscape of electronic devices and change how they are deployed across various high-stakes fields.</p>