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Development of Nanohybrid Devices for Optoelectronics and Sensors
Liu, Bo
Liu, Bo
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Abstract
As semiconductor manufacturing approach the physical limits of sub-nanometer scales, the industry faces escalating challenges. Traditional "top-down" fabrication methods are increasingly inadequate due to rising complexities and costs, which threaten the sustainability of Moore's pace of advancement. This situation has prompted the exploration of "bottom-up" approaches, which assemble pre-synthesized low-dimensional materials and nanostructures onto substrates. These methods offer an alternative solution to overcome the limitations of extreme miniaturization, enhancing device functionality while helping to control escalating costs.
In light of these advancements, nanomaterials such as zero-dimensional quantum dots (QDs) and two-dimensional graphene play pivotal roles due to their unique properties that differ significantly from their bulk counterparts. For example, QDs exhibit enhanced light absorption capabilities through quantum confinement, whereas graphene provides exceptional conductivity and mechanical strength. However, each material's inherent limitations - quantum tunneling in QDs and bandgap tuning challenges in graphene - can hinder their standalone applications in fields requiring efficient light-matter interactions. This dissertation explores the concept of nanohybrids, which synergistically combines two or more nanomaterials to mitigate their individual weaknesses and enhance their collective strengths. These nanohybrids, particularly in configurations like QDs integrated with graphene, demonstrate significant potential for creating high-performance optoelectronic devices and sensitive gas sensors, while also allowing us to explore new quantum physics that are not observable in conventional devices and sensors.
Building on these insights, this dissertation addresses specific challenges by focusing on two distinct nanohybrid systems. The first involves integrating QDs with graphene (QD/Graphene nanohybrid) for optoelectronic applications, aiming to push detectivity D* to its intrinsic limit. The second focus on developing enhanced hydrogen sensors using platinum nano-catalysts coated on specially designed 3D carbon nanostructures (Pt @ 3D Carbon Nanostructure), addressing issues of nanoparticle morphology and distribution to improve the sensitivity of gas sensors.
To lay the foundation for these innovative systems, Chapter 2 introduces the fundamental principles of the materials and devices crucial to this research. It covers foundational concepts of graphene, QDs, QD/Graphene nanohybrids, localized surface plasmon resonance (LSPR) from metal nanoparticles, and carbon nanostructure-based gas sensors. This chapter sets the stage for the practical applications and enhancements detailed in subsequent chapters.
Chapter 3 investigates the noise and optoelectronic properties of HgTe QDs/graphene nanohybrids, offering key insights into the physics of quantum sensors for SWIR-MWIR photodetection at room temperature. Findings reveal that graphene's noise predominates, differing from conventional semiconductor IR detectors where thermal noise impacts signal-to-noise ratio and performance at MWIR or longer wavelengths. The study also demonstrates that QDs can effectively passivate graphene, reducing the impact of unintentional carrier doping from external contaminants, thus approaching graphene’s intrinsic noise limits. Additionally, enhancements in quantum confinement effects and graphene’s carrier mobility significantly improve photoconductive gain. Innovations with organic precursors reduce tellurium deficiencies, achieving high gains and unprecedented room temperature responsivity and detectivity in the MWIR spectrum. This research paves the way for the design of uncooled high-performance IR detectors.
Chapter 4 introduces a novel plasmonic metafilm that enhances plasmon-exciton coupling in optoelectronic devices using a cost-effective and scalable method. This involves integrating silver nanoparticles (Ag NPs) with a thin silica layer, applied via an in-situ layer-by-layer process. The resulting Ag NP-silica metafilm effectively traps light and reduces energy losses, significantly boosting the performance of nanohybrid photodetectors. Remarkably, the metafilm achieved an enhancement factor of 7.45 for perovskite photodetectors - the highest for such devices, and an enhancement factor of 5 for WS2-ND/graphene detectors. These advancements underline the plasmonic metafilm's role as a universal platform that further improves the responsivity of various nanohybrid optoelectronics through enhanced light absorption.
Chapter 5 introduces nanohybrids by employing Atomic Layer Deposition (ALD) Platinum (Pt) on 3D carbon architectures for enhanced hydrogen sensing capabilities. The first architecture integrates ALD-Pt on SWCNT/graphene nanohybrids, which significantly improves H₂ detection by utilizing the high charge mobility of graphene and catalytic properties of SWCNTs. The second innovative approach details the synthesis of single-atom Pt (SA-Pt) catalysts on vertical graphene (VG), using ALD for precise atomic-scale control, resulting in superior hydrogen sensing performance with faster response times and higher sensitivity compared to nano-Pt based sensors. Both approaches underline the potential of ALD alongside novel carbon nanostructures to advance sensor technology with improved catalytic efficiency and cost-effectiveness, setting the stage for next-generation sensing applications.
This dissertation demonstrates the practical applications of nanohybrids in optoelectronic devices and gas sensors. The results presented in this dissertation pave the way for future research to further exploit the nanohybrid systems for technological innovations, potentially transforming the landscape of materials science and device engineering.
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Date
2024-01-01
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University of Kansas
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Keywords
Physics, Condensed matter physics, Materials Science, Devices, Gas Sensors, Low-dimensional Materials, Nanohybrids, Optoelectronics