Engineering Commons^™

Development Of Pulsed Laser Deposited Tio2, Zno And Azo Thin Uv-Protection Films For Enhanced Perovskite Photostability, Kate Lochhead

Electronic Thesis and Dissertation Repository

Perovskite solar cells are an emerging sustainable energy conversion technology with the potential to provide relief from the global energy crisis. However, the UV-induced degradation of perovskites has been a barrier to commercialization. Thin film encapsulation represents a promising solution for extending device lifetimes. Three materials with suitable bandgaps for blocking UV light are identified: TiO₂, ZnO and AZO. Herein, the optical properties of TiO₂, ZnO and AZO thin films grown by room-temperature pulsed laser deposition are optimized by varying the oxygen partial pressure during deposition. UV-Vis spectroscopy reveals facile bandgap tuning via the concentration of …

Performance Of Pld Grown Zno Thin Film As A Thin Film Transistor, Shahidul Asif

MSU Graduate Theses

The performance of ZnO thin film (grown in different parameters) as a thin film transistor (TFT) is the focus of this study. ZnO is renowned for being n-type semiconductor naturally which was utilized in fabricating a thin film transistor here. This thesis is compared the performance of ZnO thin film transistor by growing the thin film using pulsed laser deposition (PLD) on two slightly different substrates at different temperatures in an optimal 0.1 milli bar oxygen pressure which was later analyzed using other material characterization methods. The substrates were both Si (100) but had different resistivity due to different amount …

Comparative Characterization Of Molybdenum Oxide Thin Films Grown On Various Substrates Using Temporally Different Pulsed Laser Deposition Techniques, Krishna Harsha Puppala

MSU Graduate Theses

Pulsed Laser Deposition (PLD) technique, with its vast tunability in terms of thin film fabrication has been the center of this study. By changing the temporal component of the laser source used for deposition into the femtosecond (fs) regime, interesting structural, morphological changes can be achieved which may prove to be beneficial for photocatalytic applications. In particular, molybdenum oxide thin films, which are the less well-studied and potentially newer candidates for photocatalysis applications have been chosen for investigation. Hence, a detailed characterization study of molybdenum oxide thin films synthesized using femtosecond-based (f-PLD) and nanosecond-based (n-PLD) techniques, was carried out in …

Investigation Of Nbnx Thin Films And Nanoparticles Grown By Pulsed Laser Deposition And Thermal Diffusion, Ashraf Hassan Farha

Electrical & Computer Engineering Theses & Dissertations

Niobium nitride films (NbNx) were grown on Nb and Si (100) substrates using pulsed laser deposition (PLD), laser heating, and thermal diffusion methods. Niobium nitride films were deposited on Nb substrates using PLD with a Q-switched Nd: YAG laser (λ = 1064 nm, 40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, different nitrogen background pressures and deposition temperatures. The effect of changing PLD parameters for films done by PLD was studied. The seen observations establish guidelines for adjusting the laser parameters to achieve the desired morphology and phase of the grown NbNx films.

When the …

Excitation-Induced Ge Quantum Dot Growth On Si(100)-2x1 By Pulsed Laser Deposition, Ali Oguz Er

Physics Theses & Dissertations

Self-assembled Ge quantum dots (QD) are grown on Si(100)-(2×1) with laser excitation during growth processes by pulsed laser deposition (PLD). In situ reflection-high energy electron diffraction (RHEED) and post-deposition atomic force microscopy (AFM) are used to study the growth dynamics and morphology of the QDs. A Q-switched Nd:YAG laser (λ = 1064 nm, 40 ns pulse width, 5 J/cm² fluence, and 10 Hz repetition rate) were used to ablate germanium and irradiate the silicon substrate. Ge QD formation on Si(100)-(2×1) with different substrate temperatures and excitation laser energy densities was studied. The excitation laser reduces the epitaxial growth temperature …

Surface Dynamics Of Silicon Low-Index Surfaces Studied By Reflection High-Energy Electron Diffraction, Ibrahim El-Kholy

Electrical & Computer Engineering Theses & Dissertations

Surface morphology during the growth of Si on Si(111)-(7x7) by femtosecond pulsed laser deposition (fsPLD) is studied using reflection high-energy electron diffraction (RHEED) at different temperatures. The growth of Si on Si(111) has received considerable attention as a model system of homoepitaxy. PLD is a deposition technique that uses much more energetic species (atoms and ions) compared to other physical vapor deposition (PVD), such as in molecular beam epitaxy. In this work, in situ reflection high energy electron diffraction (RHEED) was used to study the dynamics of PLD of Si on Si(111)-(7x7). Epitaxial growth of Si/Si(111)-(7x7) at temperatures as low …

Growth And Characterization Of Chromium Doped Indium Oxide Diluted Magnetic Semiconductors, Ndubuisi Benjamin Ukah

MSU Graduate Theses

Recently, enormous research efforts have been directed at diluted magnetic semiconductors (DMS) critical for realization for multi-functional spintronic devices. However, the origin of electronic and magnetic properties in DMS is not well understood. This study is aimed to better understand the structural, optical, magnetic, and magneto-transport property relationships of Cr-doped In2O3 (In2O3:Cr) DMS grown under different partial oxygen pressures on sapphire substrates using pulsed laser deposition technique. The thin films were characterized using various state-of-the-art techniques such as x-ray diffraction (XRD), UV-VIS spectroscopy, magnetotransport, and SQUID magnetometer. Expansions in lattice parameter (10.10 Å to 10.34 Å) and crystal size (13.9 …

Reflection High-Energy Electron Diffraction Studies Of Indium Phosphide (100) And Growth On Indium And Indium Nitride On Silicon (100), Mohamed Abd-Elsattar Hafez

Electrical & Computer Engineering Theses & Dissertations

Study of the effects of atomic hydrogen exposure on structure and morphology of semiconductor surfaces is important for fundamental properties and applications. In this dissertation, the electron yield of a hydrogen-cleaned indium phosphide (InP) surface was measured and correlated to the development of the surface morphology, which was monitored by in situ reflection high-energy electron diffraction (RHEED). Atomic hydrogen treatment produced a clean, well-ordered, and (2x4)-reconstructed InP(100) surface. The quantum efficiency, after activation to negative electron affinity, and the secondary electron emission were shown to increase with hydrogen cleaning time. RHEED patterns of low-index InP(100) surface were modified by the …

Controlled-Stress Large-Area Pulsed Laser Deposition Of Yttria Stabilized Zirconia, Paul C. Rounsavall

Theses and Dissertations

The US Air Force has need of parabolic-shaped membrane mirrors for surveillance satellites. The current polymer membrane technology has been unable to overcome shape deformation problems caused by intrinsic stresses from the membrane casting and mounting processes. One proposed solution was to coat the membrane mirrors with a stressed coating to compensate for shape deformations. Thus, the research presented in this dissertation produced controlled-stress large-area pulsed laser deposition (PLD) grown thin films on polymer substrates and investigated optical time-of-flight (TOF) sensor systems and Raman spectroscopy for control for the PLD process with respect to thin film stress. Initially, the PLD-grown …

Preparation And Surface Studies Of Negative Electron Affinity Semiconductors Photocathodes, Khaled A. Elamrawi

Electrical & Computer Engineering Theses & Dissertations

Fabrication of high quantum efficiency, long lifetime negative electron affinity photocathodes is important for applications such as photomultipliers, image intensifiers, electron beam lithography, electron microscopy, and polarized electron sources. The surface cleanliness of the III-V semiconductor photocathode is crucial in obtaining high photosensitivity.

GaAs(100) and InP(100) photocathodes are prepared by atomic hydrogen cleaning. The cleaning effect on the photocathode performance is discussed. The surface degradation mechanisms which reduce the photocathode lifetime are presented. The photocathode surface cleanliness, structure, and morphology are studied using reflection high-energy electron diffraction (RHEED).

Quantum efficiencies of ∼14% and 8% are obtained for GaAs and InP, …