Ultrafast plasmonic modulators are becoming essential for next-generation optoelectronic systems, yet their speed is fundamentally limited by conventional semiconductor carrier dynamics. To address this bottle-neck, this study investigates hot-electron–driven plasmonic modulation in engineered noble-metal nanoantenna arrays, leveraging the sub-picosecond thermalization dynamics of non-equilibrium electrons to achieve femtosecond optical switching. The methodology integrates nanoscale fabrication of gold and silver dipole nanoantenna, resonant optical excitation, and time-resolved pump–probe spectroscopy, supported by a Multiphysics simulation framework combining the two-temperature model, plasmonic field enhancement, and electron–phonon coupling. Experimental results reveal a modulation speed below 200 fs with a modulation depth of 15–18%, accompanied by a rapid spectral shift in localized surface plasmon resonances, confirming the strong contribution of hot-electron–induced refractive index variation. The analysis further shows that enhanced confinement and asymmetric antenna geometry significantly increase hot-carrier density and improve switching performance without inducing thermal degradation. These insights demonstrate that hot-electron dynamics offer a viable pathway for scalable, ultrafast plasmonic modulators, enabling compact, broadband, and CMOS-compatible designs suitable for high-speed photonic interconnects, terahertz links, and on-chip optical switching.

Hydrogen energy has garnered widespread attention in recent years. Among the various hydrogen production methods, electrocatalytic water splitting is undoubtedly the most promising approach. For this reason, this thesis explores the influence of incorporating different metals on catalyst performance. In electrocatalytic experiments, the ternary metal catalyst NiCo 2 O 4 @CoMoS exhibited an overpotential of 386.1 mV in the oxygen evolution reaction (OER) with a relatively high polarization, a Tafel slope of 227.31 mV dec 1 , indicating low catalytic activity but optimal intrinsic material activity (0.01474 mF cm −2 ). In the hydrogen evolution reaction (HER), the ternary metal catalyst NiCo 2 O 4 @CoMoS showed the highest overpotential of 386.1 mV, with a Tafel slope of 50.09 mV dec −1 , demonstrating the best intrinsic material activity and a high number of active sites. In simulated seawater conditions, the ternary metal catalyst NiCo 2 O 4 @CoMoS exhibited an overpotential of 400.4 mV under oxygen evolution conditions, indicating the highest catalytic activity and superior intrinsic material performance.

The relentless miniaturization of consumer electronics drives the demand for high-performance micro-camera modules, where imaging quality is critically dependent on precise lens-sensor alignment. Conventional methods for assessing optical performance, such as spatial frequency response (SFR) measurements, are accurate but inherently offline and slow, creating a bottleneck for mass production. This work introduces a rapid, in-line inspection methodology that leverages computational vision to predict imaging quality through the quantification of lens centration error. We establish a statistical baseline using traditional SFR evaluation and then employ a telecentric imaging system to extract geometric features and measure assembly misalignments. A linear regression model reveals a significant negative correlation between the measured centration error and the SFR value. To validate industrial applicability, we conducted an online inspection of 300 consecutively manufactured modules. The results showed that modules with good concentricity, defined as having an alignment error of 25 micrometers or less, exhibited SFR values that were on average 15% higher than those of poorly aligned modules. The ability to correlate structural precision with functional optical output provides a scalable and efficient pathway for quality assurance in the production of next-generation devices, including integrated photonic circuits and metasurfaces, bridging a critical gap between macro-scale assembly and nanoscale precision requirements.

In this study, we have explored the possibility of inducing magnetism in Cu 2 ZnSnS 4 (CZTS), which is a promising earth-abundant and nontoxic absorbent material. Although CZTS has been widely investigated for photovoltaic applications, achieving magnetism by doping CZTS can pave the way for novel applications. Spin polarized density functional theory has been used to explore the magnetic properties of doped CZTS. To create extrinsic defects, we substitute one Zn cation with Fe, Ni, Co, Cr and Mn cations. Our magnetic properties results show that Fe Zn 0 , Fe Zn −1 and Co Zn 0 induce magnetization in CZTS with significant magnetic moment. Additionally, Ni and Co defects result in magnetic character with different magnetic moments depending on defect charge states, indicating that they are good candidates for obtaining magnetic character in CZTS. Thus, our study shows that CZTS substitutional defects can be used to attain magnetic character in CZTS, which opens doors to potential applications in spintronics.

In etching processes for next-generation semiconductor devices, the precise fabrication of high-aspect-ratio (HAR) structures and adoption of low-global warming potential (GWP) gases in accordance with environmental regulations are critically important. This study systematically investigates the etching behavior, selectivity, and surface reaction mechanisms of SiO 2 and Si 3 N 4 under low-temperature plasma conditions, employing isomers of C 4 H 2 F 6 (C 4 H 2 F 6 -e and C 4 H 2 F 6 -iso) based on low-GWP gas chemistry. Etching experiments were conducted using an inductively coupled plasma (ICP) system, under varying temperature, source power, and oxygen flow rate. Etch rates and selectivity were measured using an ellipsometer and profilometer, whereas reactive plasma species were characterized through optical emission spectroscopy (OES). Surface chemical states were quantitatively analyzed using X-ray photoelectron spectroscopy (XPS). As temperature decreased, the etch rate of SiO 2 increased, whereas that of Si 3 N 4 decreased. In contrast, increasing source power led to higher etch rates for both materials, although the resulting changes in selectivity remained negligible. With increased oxygen flow, the etch rate of SiO 2 decreased whereas that of Si 3 N 4 increased, indicating a distinct difference in their reactive behavior. Notably, C 4 H 2 F 6 -e demonstrated a more pronounced sensitivity to hydrogen radical generation and surface reactions compared with the iso form. The XPS analysis further revealed that, under the C 4 H 2 F 6 -e condition, elevated oxygen flow suppressed CF x polymer formation while enhancing C–C bonding, thereby diminishing the etch-inhibiting layer on the Si 3 N 4 surface. Cross-sectional scanning electron microscopy (SEM) analysis confirmed minimal damage to the amorphous carbon layer (ACL) mask and the preservation of well-defined vertical profiles. These findings demonstrate that C 4 H 2 F 6 -e provides superior process controllability under low-temperature conditions compared with C 4 H 2 F 6 -iso, under-scoring its strong potential for implementation in next-generation high aspect ratio contact (HARC) etching processes.

The rapid advancement of programmable logic devices (PLDs) and field-programmable gate arrays (FPGAs) has enabled the development of adaptive VLSI architectures optimized for next-generation wireless communication systems. This research focuses on RFID and Wireless Sensor Network (WSN) applications, integrating AI-driven optimization techniques to enhance power efficiency, processing speed, and system adaptability. A hybrid AI-based hardware optimization technique, combining Reinforcement Learning (RL) and Genetic Algorithm (GA), is introduced to improve resource utilization and reduce latency. Additionally, an AI-Optimized Dynamic Frequency Scaling (DFS) technique is implemented to adjust FPGA operating frequencies in real-time, achieving a power reduction of 27.6% while maintaining high computational efficiency. Processor implementation for RFID-based power-saving appliances, reducing power consumption by 32.5% compared to conventional approaches. Hardware realization of an optimized anti-collision algorithm for RFID, achieving a 24.8% increase in tag identification speed. FPGA-based security architecture integrating lightweight cryptographic techniques, enhancing data security with a 96.2% encryption success rate and 25% lower hard-ware resource usage. Power-efficient WSN node implementation using an adaptive localization algorithm, reducing localization errors by 18.4% and extending node lifespan by 29.3%. Low-power CORDIC algorithm-based DPSK modem implementation with 32.1% lower latency in real-time signal processing applications. AI-Optimized DFS technique, reducing dynamic power consumption by 27.6% and improving computational throughput by 22.7%, making FPGA implementations more energy-efficient. The designs were developed using VHDL-based high-level hardware description, simulated in Xilinx ISE 14.3, and implemented on Virtex-5, Spartan-6, and Kintex-7 FPGA platforms. Performance evaluations and comparative studies with existing models confirm significant improvements in power efficiency, processing speed, and adaptability. The findings contribute to the development of high-performance, power-efficient, and scalable VLSI architectures for RFID and WSN applications, paving the way for next-generation secure and intelligent wireless communication systems.

Continuous physiological signal acquisition within implantable health monitoring systems demands extremely low-power and leakage-tolerant circuit architectures to ensure long-term operation under stringent biomedical constraints. This paper proposes an Ultra-Low-Leakage FinFET-Assisted Wireless Sensor Framework (ULL-FSF) designed for next-generation implantable biosensors monitoring cardiac, neural, and metabolic activities. The proposed architecture integrates 10 nm FinFET-based analog front-end amplifiers with a sub-threshold biasing network and adaptive power-gating controller, achieving significant leakage current suppression. Through a multi-threshold FinFET topology and dynamic body-bias control, the system achieves 78.4% leakage reduction and 65.7% total power savings compared with equivalent 45 nm CMOS counterparts. A low-power RF transceiver operating at 2.45 GHz enables secure, short-range telemetry with energy consumption of 18.2 pJ/bit, while the analog-to-digital converter (ADC) exhibits an ENOB of 9.8 bits at a sampling rate of 500 kS/s. The wireless link efficiency of 92.3% and biological tissue penetration depth of 11 mm ensure stable communication through soft tissue layers. Fabricated in Cadence Virtuoso using Synopsys 10 nm FinFET PDK, post-layout simulations report a total power dissipation of 18.6 μ W and an average leakage current of 4.7 nA under a 0.6 V supply, validating its suitability for long-term implantable biosensing nodes. Experimental results confirm a battery life extension of 2.8×, while maintaining signal-to-noise ratio (SNR) >58 dB during continuous ECG and glucose sensing operations. The ULL-FSF architecture demonstrates that combining FinFET leakage-resilient circuits with adaptive power scheduling can substantially enhance the operational lifetime and reliability of biomedical implants, paving the way for sustainable and miniaturized health-monitoring ecosystems.

The development of efficient non-precious metal electrocatalysts is crucial for advancing the hydrogen energy industry. In this study, we synthesized NiF 2 /CoF 2 composite materials and investigated their electrocatalytic performance for the oxygen evolution reaction (OER). Structural and morphological characterizations confirmed the successful formation of highly crystalline NiF 2 /CoF 2 nanosheets with a well-defined layered architecture. Electrochemical tests revealed that the NiF 2 /CoF 2 electrode exhibited superior OER activity, demonstrating a low overpotential of 191 mV at 10 mA cm −2 and a Tafel slope of 46.6 mV dec −1 , indicating favorable reaction kinetics. Notably, the NiF 2 /CoF 2 sample displayed a high electrochemical double-layer capacitance (C 5l ) of 0.2228 F cm −2 , suggesting a large electrochemical active surface area (ECSA) and abundant accessible active sites. This enhanced catalytic performance is attributed to the synergistic interaction between NiF 2 and CoF 2 , which facilitates efficient charge transfer and strong adsorption of water molecules. Additionally, the NiF 2 /CoF 2 electrode demonstrated excellent stability during prolonged electrolysis, making it a promising candidate for practical water-splitting applications. This work provides valuable insights into the design of cost-effective and high-performance electrocatalysts for sustainable hydrogen production.

Waveguide crossings are essential yet problematic components in photonic integrated circuits, often introducing significant insertion loss and crosstalk that degrade system performance. This work presents a novel approach utilizing hybrid surface plasmon polaritons (HSPPs) to create ultra-compact waveguide crossings with improved crosstalk characteristics. Unlike conventional silicon waveguide crossings that rely on bulky tapered designs, our proposed structure integrates a nanoscale gold-SiO 2 -silicon hybrid plasmonic interface at the intersection region. Through detailed theoretical analysis and numerical simulations, we demonstrate that this configuration achieves subwavelength optical confinement while maintaining reasonable propagation lengths. The optimized device measures only 0.6 μ m × 0.6 μ m, representing a significant footprint reduction compared to traditional designs. At the telecommunications wavelength of 1550 nm, experimental results show the hybrid crossing exhibits insertion losses only 0.7 dB higher than comparable silicon waveguide crossings, while simultaneously reducing crosstalk by more than 4 dB. The performance stems from the unique electromagnetic field distribution enabled by the hybrid plasmonic mode, which strongly confines energy at the metal-dielectric interface while suppressing unwanted coupling to adjacent waveguides. Additional parametric studies reveal the critical relationship between SiO 2 spacer thickness and device performance, with a 20 nm oxide layer providing optimal balance between loss and crosstalk suppression. These findings suggest hybrid plasmonic waveguide crossings could enable higher density photonic integration while maintaining acceptable signal integrity, particularly beneficial for applications requiring tight packing of optical interconnects.

Lead halide perovskite nanocrystals (NCs) have demonstrated exceptional optoelectronic properties, making them promising candidates for applications in photovoltaics and photocatalysis. However, their inherent toxicity and instability pose significant environmental and operational challenges. To address these limitations, this study presents a facile, scalable, and environmentally benign ultrasonic-assisted one-pot colloidal synthesis of lead-free Cs2AgBiBr6 double perovskite nanocrystals (DPNCs). The synthesized NCs exhibit a narrow bandgap of 1.92 eV, making them highly suitable for visible-light absorption. Structural characterization via X-ray diffraction (XRD) confirms a cubic crystal structure with lattice parameters of 11.28 Å and space group Fm3-m, while transmission electron microscopy (TEM) reveals well-dispersed spherical NCs with an average size of ~15 nm. The optical properties were investigated using UV-Vis spectroscopy, demonstrating strong absorption at 437 nm. The photocatalytic performance of Cs2AgBiBr6 NCs was evaluated through the degradation of Rhodamine B (RhB) under visible light, achieving an impressive 93% removal efficiency within 70 minutes. The reaction kinetics followed a pseudo-zero-order model, with superoxide radicals (·O2-) identified as the primary active species responsible for dye degradation. The negatively charged surface of Cs2AgBiBr6 NCs facilitates electrostatic interactions with cationic dyes, enhancing photocatalytic efficiency.