Plazmonik nanoyapılar ve mikrogerinim mühendisliği ile II-VI ve üçlü kalkojenit ince filmlerde geliştirilmiş fotodedeksiyon

The quest for high-performance photodetectors necessitates innovative strategies to transcend limitations in light absorption, carrier transport, and defect-mediated losses. This thesis presents a comprehensive investigation into the synergistic integration of plasmonic nanostructuring and microstrain engineering to elevate photodetector performance in II-VI (CdS) and ternary chalcogenide (𝐶𝑢2𝑆𝑛𝑆3and 𝐶𝑢2𝑍𝑛𝑆𝑛𝑆4) semiconductor thin films. Utilizing pulsed laser deposition (PLD) for precise control over stoichiometry and film morphology, the study elucidates how embedded gold nanoparticles (AuNPs) simultaneously modulate light–matter interactions and internal lattice strain, yielding improved optoelectronic performance across the ultraviolet, visible, and solar spectral regions. CdS-based photodetectors exhibited outstanding ultraviolet sensitivity, with responsivity reaching 13.86 A/W and detectivity approaching 1.1×10¹² Jones under 365 nm illumination. This enhancement is attributed to near-field plasmonic coupling effects and a significant reduction in microstrain (~2.04×10⁻³), particularly at an optimized film thickness of ~100 nm, which aligns the plasmonic field penetration with the material's optical absorption depth. Structural analyses revealed improved crystallinity and diminished defect densities, as evidenced by sharper X-ray diffraction peaks and decreased full width at half maximum (FWHM) values. In Au/𝐶𝑢2𝑆𝑛𝑆3heterostructures, an anomalous negative photoconductivity (NPC) mechanism was uncovered and rigorously characterized. Elevated Urbach energy values (>70 meV) signified a high density of trap states, while Joule heating experiments partially mitigated the NPC effect via thermally induced defect reorganization. This finding highlights a pivotal insight: plasmonic enhancement efficacy is fundamentally contingent upon effective defect suppression within the semiconductor matrix. The Cu2ZnSnS4 system demonstrated compelling evidence of microstrain-mediated performance enhancement. Strategic incorporation of AuNP "sandwich" structures reduced lattice strain from 3.38×10⁻³ to 1.94×10⁻³, directly correlating with faster photoresponse kinetics, from >150 ms to 95.4 ms under standard 1 Sun illumination. Spectroscopic analyses confirmed extended absorption into the near-infrared region, attributable to plasmon-induced optical amplification. Comprehensive structural and optoelectronic characterizations across all material systems, including high-resolution X-ray diffraction, confocal Raman spectroscopy, and field-emission scanning electron microscopy, enabled the development of a unified theoretical framework. This model identifies critical design parameters such as strain thresholds (<2×10⁻³), plasmonic coupling efficiency, trap state density modulation, and grain boundary engineering as dominant factors governing optimized photodetector behaviour. The findings not only set new performance benchmarks for wide- and narrow-bandgap semiconductors but also present scalable, fabrication-compatible methodologies for incorporating plasmonic nanostructures into functional optoelectronic architectures. This work lays a foundational platform for photodetectors with enhanced sensitivity, spectral tunability, and temporal response characteristics, with far-reaching implications for applications in environmental monitoring, wearable sensors, high-speed optical communication, and solar energy harvesting.