Engineering Commons^™

Fabrication Of Two-Dimensional Material-Based Nano-Capacitors Using Bismuth Selenite (Bi2seo5) To Study Its Dielectric Properties, Major Kc

McKelvey School of Engineering Theses & Dissertations

In recent years, the demand for high-performance micro and nanodevices has surged, necessitating the exploration of novel dielectric materials to replace conventional silicon dioxide. Following the continuation of the Moorse law, as device dimensions reduce to nanoscale levels, the properties of silicon dioxide can degrade, leading to issues such as increased leakage current and reduced gate control. Materials with superior electrical properties, such as higher dielectric constant, lower leakage current, and better thermal stability allowing for the development of faster, more efficient, and more reliable devices are in higher demand than ever. Two-dimensional layered semiconductor nanomaterials represented by compounds such …

Two-Dimensional Field Effect Transistor, Yimeng Li

McKelvey School of Engineering Theses & Dissertations

As silicon-based field-effect transistors (FETs) approach their physical limits with channel lengths approaching 5 nm, the search for new semiconductor materials that can surpass this limit has become urgent. Two-dimensional layered semiconductor nanomaterials, represented by graphene, have emerged as promising candidates due to their unique physical, mechanical, and chemical properties. Unlike traditional silicon-based FETs, two dimensional (2D) layered nanomaterials are held together by van der Waals forces between layers, with no dangling bonds on the material surface, which can effectively address the short-channel effect issue faced by traditional silicon-based FETs. However, unlike traditional silicon-based FETs, which have matured fabrication systems, …

Confined Growth Of Perovskite Stabilized By Strain Engineering, Xucheng Tao

McKelvey School of Engineering Theses & Dissertations

Halide perovskite has been extensively studied for its excellent optoelectronic properties. In this project, we want to explore some range of band gap that conventional 2D materials could not have. To overcome this challenge, we aimed to produce two-dimensional (2D) perovskites with large scale which is suitable for device fabrication and improve its stability using strain engineering. To prepare such 2D perovskite, we tried 2D transformation first and then decided to use confined growth to optimize result. For strain engineering, we employed sputtered nickel as an external stressor.

So far, we have produced multilayer polycrystalline perovskites material close to atomic …

Research Of Electro-Optical Effect In Metal Halide Perovskites By Fabry-Perot Interometer Method, Hanxiang Yin

McKelvey School of Engineering Theses & Dissertations

Perovskites have been investigated a lot by present and reported with outstanding optoelectronic properties. However, so far there is no publications about another important property, the electro-optical (EO) effect which is related to important applications in photolithography. This thesis is mainly mean to calculate the EO constants of one kind of organic perovskite material, CH₃NH₃PbI₃, which has been reported to have good capability of forming film by spin-coating, through the way of putting the film of CH₃NH₃PbI₃ between two layers of metal mirrors to build a Fabry-Perot interferometer and …

Single-Step, Atmospheric Pressure Chemical Vapor Deposition Of Methylammonium Bismuth Iodide Thin Films, Xiao Chen

McKelvey School of Engineering Theses & Dissertations

Lead halide perovskites (CH₃NH₃PbI₃ and its variants) are promising solar cell absorber materials. Though the reported power conversion efficiencies of lead halide perovskite solar cells (up to 21%) are competitive with commercial silicon solar cells, lead toxicity in these perovskites present a challenge to further scale-up and eventual commercialization. Recently, bismuth (Bi³⁺) based organic halide perovskite has drawn attention as a substitution for lead-free perovskites, since it is a non-toxic 6p-block element, isoelectronic with Pb²⁺. Methylammonium bismuth iodide ((CH₃NH₃)₃Bi₂I₉) is reported …

Contact Radius And Insulator-Metal Transition In Films Comprised Of Touching Semiconductor Nanocrystals, Deanna M. Lanigan

McKelvey School of Engineering Theses & Dissertations

Nanocrystal assemblies are being explored for a number of optoelectronic applications such as transparent conductors, photovoltaic solar cells, and electrochromic windows. Majority carrier transport is important for these applications, yet it remains relatively poorly understood in films comprised of touching nanocrystals. Specifically, the underlying structural parameters expected to determine the transport mechanism have not been fully elucidated. In this report, we demonstrate experimentally that the contact radius, between touching heavily doped ZnO nanocrystals, controls the electron transport mechanism. Spherical nanocrystals are considered, which are connected by a circular area. The radius of this circular area is the contact radius. For …

Single Cuo Nanowires Electrical Properties And Application On Photoelectrochemical Water Splitting, Junnan Wu

McKelvey School of Engineering Theses & Dissertations

Charge transport in single crystal, p type copper oxide (CuO) nanowires (NWs) was studied through temperature based (120 K – 400 K) current-voltage (I-V) measurements of 2-terminal single NW devices. Individual CuO NWs with an average diameter of 220 nm were attached to Au electrodes 2.5 µm apart, using a dielectrophoresis method. I-V curves showed a transition from linear behavior at low bias to strong power law dependence (I ~ V^a) at high bias, which can be attributed to space charge limited current (SCLC) mechanism. At low electrical fields (< 0.89 × 10³ V·cm^-1), the number of …