Physical Sciences and Mathematics Commons^™

Synthesis And Characterization Of A Zirconium (Zr) Thin Film On Si(100) Via Pulsed Laser Deposition, Zikrulloh Khuzhakulov

Masters Theses & Specialist Projects

This study investigates the synthesis and characterization of zirconium (Zr) thin films deposited on Si(100) substrates using pulsed laser deposition (PLD). The effects of two laser wavelengths (1064 nm and 532 nm), various substrate temperatures (25 °C, 300 °C, and 500 °C), and different laser fluences (0.25, 0.5, 1.0 J/cm²) on the properties of the Zr films were examined. Results indicated that smoother films were achieved with the 1064 nm wavelength, while surface roughness increased with higher fluences. Optimal crystalline films were obtained at a substrate temperature of 300 °C for both wavelengths. X-ray diffraction (XRD), scanning electron microscopy (SEM), …

Bioactivity And Structural Properties Of Hydroxyapatite On Ti6a|4v And Si(100) Surfaces By Pulsed Laser Deposition, Salizhan Kylchbekov

Masters Theses & Specialist Projects

Although biomedical implant technology is very advanced, there are still caveats in terms of biocompatibility properties because metals are inert to biological processes such as osseointegration, cell growth, and cell adhesion. This results in statistically significant complications and opens rooms for improvements. Among many techniques to improve this problem, coating the metal surface with biologically functional materials has resulted in the best performances. Hydroxyapatite (HAP), Ca_₁₀(PO_₄)_₆(OH)_₂, is the most stable form of calcium phosphates in human body environment and is functional in key processes such as ion exchange, osteoblast (bone cells) formation, …

Study Of Electrical And Magnetic Properties Of Ni/Nio Nanocomposite Thin Film, Bishwajite Karmakar

MSU Graduate Theses

In this thesis, detailed magnetic and electrical transport properties of composite thin films consisting of antiferromagnetic NiO, and ferromagnetic Ni have been studied. Highly oriented NiO thin films were grown on sapphire (0001) substrate using pulsed laser deposition with varying growth parameters such as oxygen pressure of the chamber and the substrate temperature. To obtain various percentage mixtures of Ni and NiO by means of introducing point defects (oxygen vacancies) into the NiO crystal structure, the as-grown films were annealed in forming gas (Ar:96% and H2:4%) at a fixed temperature of 600C and varying annealing time (0.5h to 6h). X-ray …

Structural, Electrical And Optical Properties Of Copper Oxide Phase Mixture: An Active Layer Of Solar Cell, Rifat Ara Shams

MSU Graduate Theses

Both CuO and Cu2O have been well studied and implemented individually as an active layer of a solar cell from early age of manufacturing. A mixture of these two-phase contents at different ratios can bring variance in absorbance which can present new and diverse aspect in solar cell fabrication with added efficiency. Previous works were successful to vary the phase mixture, and the nanostructures provided very high absorption co-efficient but poor optical response on electrical conductivity. The goal of this research is to find out the optimum parameter for the phase mixture of copper oxide with high absorption coefficient as …

Interface-Induced Lattice Structure And Magnetism In Ultrathin Transition Metal Oxide Trilayers, David Howe

LSU Doctoral Dissertations

The study of magnetism has been a rich playground in condensed matter physics due to the multiple mechanisms capable of producing the effect and its relationship to multiple characteristics of a material. Transition metal oxides (TMOs) have been of particular interest for ongoing research into magnetic phenomenon due to the abundance of interesting physical phenomena found in member systems such as colossal magnetoresistance, skyrmion formation, and interface-driven 2D electron gases. Thin films introduce an additional thickness-dependent element, where reduction below a critical thickness eliminates the magnetic coherence of a system and FM order is lost. The atomic structure of these …

Effect Of Annealing On The Structural, Surface Morphology And Optical Properties For Cdo:Pbo Composite Thin Films, Rasha Hamid Ahmed, Maad Mohammed Ameen

Al-Qadisiyah Journal of Pure Science

Thin films of pure cadmium oxide films (CdO) and composite with lead oxide (PbO) at different atomic ratios were prepared by pulsed laser deposition under vacuum usingpulsed laser of ND-YAG from CdO and CdO:PbO targets. The prepared thin films were characterized by different technique before and after annealing. The X-ray diffraction shows polycrystalline structures of cubic CdO phase convert tosample of mixed phases for composites. The AFM images illustratedecreasing the particle diameter and increasingsurface roughness with increasing the PbO ratio in composite. While, annealing cause to increase the particle size and reduce roughness. The optical absorbance increased with the PbO …

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 …

Effect Of Hydrogen Exposure On The Electronic And Optical Properties Of Insulating Titanates, John G. Connell

Theses and Dissertations--Physics and Astronomy

Hydrogen exposure of insulating d⁰-titanates, such as SrTiO₃ (STO), has displayed the formation of intriguing conducting states. These conducting states form through the use of forming gas (N₂/H₂) annealing or hydrogen plasma exposure, where hydrogen gas is exposed to high energy microwaves. The exposure of STO to hydrogen causes metallic conductivity due to the introduction of hydrogen cations on some of the oxygen sites. However, the optical properties of this hydrogen-exposed STO have not been well-studied. Further, Ba_0.5Sr_0.5TiO₃ (BST), an insulating dielectric, also shows changes in its conductivity …

Transmission Electron Microscopy Analysis Of Silicon-Doped Beta-Gallium Oxide Films Grown By Pulsed Laser Deposition, Cynthia Thomason Bowers

Browse all Theses and Dissertations

Due to the large band gap of β-Ga2O3 and recent improvements toward high quality native substrates and the ability to shallow dope epitaxial β-Ga2O3 it is an attractive material for applications in power electronic devices. Such devices require advances in the areas of thin film growth and carrier concentration control to deliver high mobility films appropriate for the device structures. Transmission electron microscopy (TEM) analysis can provide information concerning doping, crystal structure, and internal strain which will be valuable to assess the role of defects and impurities on the transport properties for feedback to optimize the bulk and epitaxial growth …

Electronic And Optical Properties Of Metastable Epitaxial Thin Films Of Layered Iridates, Maryam Souri

Theses and Dissertations--Physics and Astronomy

The layered iridates such as Sr₂IrO₄ and Sr₃Ir₂O₇, have attracted substantial attention due to their novel electronic states originating from strong spin-orbit coupling and electron-correlation. Recent studies have revealed the possibilities of novel phases such as topological insulators, Weyl semimetals, and even a potential high-T_c superconducting state with a d-wave gap. However, there are still controversial issues regarding the fundamental electronic structure of these systems: the origin of the insulating gap is disputed as arising either from an antiferromagnetic ordering, i.e. Slater scheme or electron-correlation, i.e. Mott scheme. …

Selective Growth Of Epitaxial Sr2Iro4 By Controlling Plume Dimensions In Pulsed Laser Deposition, Sung S. Ambrose Seo, J. Nichols, J. Hwang, Jsaminka Terzic, John H. Gruenewald, Maryam Souri, Justin K. Thompson, John G. Connell, Gang Cao

Physics and Astronomy Faculty Publications

We report that epitaxial Sr₂IrO₄ thin-films can be selectively grown using pulsed laser deposition (PLD). Due to the competition between the Ruddlesden-Popper phases of strontium iridates (Sr_n+1Ir_nO_3n+1), conventional PLD methods often result in mixed phases of Sr₂IrO₄ (n = 1), Sr₃Ir₂O₇ (n = 2), and SrIrO₃ (n = ∞). We have discovered that reduced PLD plume dimensions and slow deposition rates are the key for stabilizing pure Sr₂IrO₄ phase thin-films, identified by real-time in-situ monitoring of their optical spectra. …

Kinetics Of Higher Lying Rb States After, Pulsed Excitation Of The D2 Transition In The Presence Of Helium, Austin J. Wallerstein

Theses and Dissertations

The Diode Pumped Alkali Laser (DPAL) is a high power, three-level laser system that employs diode bars to optically excite an alkali metal vapor. It lases along the D₁ transition, between the two lowest energy levels, ²P_1/2 and ²S_1/2. Higher lying energy states are produced at higher population density via energy pooling and multiphoton processes. Pulsed laser excitation of rubidium at approximately 1 MW=cm² has been studied at helium pressure up to 900 Torr. Emissions from energy states as high as 82D suggests modest ionization, though these intensities decrease drastically at buffer gas …

Magnetic And Transport Properties Of Nimnal Thin Films, Andriy Vovk, Minghui Yu, Leszek Malkinski, Charles O'Connor, Zhenjun Wang, Eden Durant, Jinke Tang, Vladimir Golub

Jinke Tang

The magnetic and transport properties of Ni₂MnAl thin films prepared using pulse laser deposition were investigated. It was shown that the films are granular and multiphase. Contrary to the data reported earlier we observe nonmonotonic temperature dependence of resistance with minimum in the vicinity of 100 K for the films deposited on substrates held at 773 K and negative magnetoresistance (MR) values of about 2.5% at 5 K and 1.6% at RT in magnetic field of 50 kOe. These values of MR are the highest reported up to date for Ni₂MnAl films. Large negative MR in …

Positive Exchange Bias In Epitaxial Permalloy/Mgo Integrated With Si (100), S. S. Rao, J. T. Prater, Fan Wu, S. Nori, D. Kumar, Lanping Yue, Sy_Hwang Liou, Jagdish Narayan

Sy-Hwang Liou Publications

In magnetic random access memory (MRAM) devices, soft magnetic thin film elements such as permalloy (Py) are used as unit cells of information. The epitaxial integration of these elements with the technologically important substrate Si (100) and a thorough understanding of their magnetic properties are critical for CMOS-based magnetic devices. We report on the epitaxial growth of Ni_82.5Fe_17.5 (permalloy, Py) on Si (100) using a TiN/MgO buffer layer. Initial stages of growth are characterized by the formation of discrete islands that gradually merge into a continuous film as deposition times are extended. Interestingly, we find that the …

Stm Study Of Pulsed Laser Assisted Growth Of Ge Quantum Dot On Si(1 0 0)-(2 × 1), Ali Orguz Er, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Ge quantum dot formation on Si(1 0 0)-(2 × 1) by nanosecond pulsed laser deposition under laser excitation was investigated. Scanning tunneling microscopy was used to probe the growth mode and morphology. Excitation was performed during deposition using laser energy density of 25-100 mJ/cm ². Faceted islands were achieved at a substrate temperature of ∼250 °C only when using laser excitation. The island morphology changes with increased laser excitation energy density although the faceting of the individual islands remains the same. The size of the major length of islands increases with the excitation laser energy density. A purely electronic …

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 …

Performnces Of Lini0.5Mn0.5O2 Thin Film Electrodes Prepared By Pulsed Laser Deposition, Yun-Hai Wan, Guo-Liang Yuan, Hui Xia

Journal of Electrochemistry

The all-solid-state thin-film Li-ion batteries with high energy density, power density and temperature stability are the ideal power sources for microelectronic devices. Developing new thin-film cathodes with large specific capacity is the key to their practical applications. The LiNi0.5Mn0.5O2 with a layered structure has a higher reversible capacity and better structural stability compared with traditional LiCoO2 cathode material. In this work, the LiNi0.5Mn0.5O2 thin film cathodes were prepared by pulsed laser deposition. The effects of substrate material and temperature on the microstructure, surface morphology and composition of the thin films were investigated. Rate capability and cycle performance of LiNi0.5Mn0.5O2 thin-film …

Stable Highly Conductive Zno Via Reduction Of Zn Vacancies, David C. Look, Timothy C. Droubay, Scott A. Chambers

Physics Faculty Publications

Growth of Ga-doped ZnO by pulsed laser deposition at 200 °C in an ambient of Ar and H₂produces a resistivity of 1.5 × 10⁻⁴ Ω-cm, stable to 500 °C. The resistivity can be further reduced to 1.2 × 10⁻⁴ Ω-cm by annealing on Zn foil, which reduces the compensating Zn-vacancy acceptor concentration N_A to 5 × 10¹⁹ cm⁻³, only 3% of the Ga-donor concentration N_D of 1.6 × 10²¹ cm⁻³, with N_D and N_A determined from a degenerate mobility theory. The plasmon-resonance wavelength is only 1060 …

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 …

Bi-Relaxation Behaviors In Epitaxial Multiferroic Double-Perovskite Bife0.5mn0.5o3/Caruo3 Heterostructures, Chew Khian Hooi, Zhan Q., Jiang Y., Miao J., Zhang X.

Chew Khian Hooi

Multiferroic double-perovskite BiFe0.5Mn0.5O3 thin film heterostructures were epitaxially grown on CaRuO3-buffered (001) SrTiO3 by pulse laser deposition. Typical Vogel-Fulcher relaxorlike dielectric and magnetic susceptibilities were observed, implying the film exhibits the properties of an electric relaxor and a magnetic relaxor. Polarization and size of polar nanoregions (PNRs) were determined by fitting the dielectric constant to a multi-polarization mechanism model. It was found that PNRs of 7-11 nm decrease from 0.67 mu C/cm(2) to 0.11 mu C/cm(2), as the temperature increases from 380 K to 460 K. A weak ferromagnetism was observed via magnetic hysteresis loops up to 300 K. (C) …

Pulsed Laser Deposition Of Graphite Counter Electrodes For Dye-Sensitized Solar Cells, Krishna P. Acharya, Himal Khatri, Sylvain Marsillac, Bruno Ullrich, Pavel Anzenbacher, Mikhail Zamkov

Electrical & Computer Engineering Faculty Publications

We report on pulsed laser deposition of graphite onto flexible plastic and conductive glass substrates for use as a counter electrode in dye-sensitized solar cells. The efficiency of as-prepared graphite electrodes was tested using CdS-sensitized solar cell architecture resulting in external quantum efficiency comparable to that of conventional platinum counter electrodes. This work highlights the possibility of using pulsed laser deposited graphite as a low-cost alternative to platinum, which could be fabricated both on flexible and rigid substrates.

Highly Conductive Zno Grown By Pulsed Laser Deposition In Pure Ar, Robin C. Scott, Kevin D. Leedy, Burhan Bayraktaroglu, David C. Look, Yong-Hang Zhang

Physics Faculty Publications

Ga-doped ZnO was deposited by pulsed laser deposition at 200 °C on SiO₂/Si, Al₂O₃, or quartz in 10 mTorr of pure Ar. The as-grown, bulk resistivity at 300 K is 1.8×10⁻⁴ Ω cm, three-times lower than that of films deposited at 200 °C in 10 mTorr of O₂ followed by an anneal at 400 °C in forming gas. Furthermore, depth uniformity of the electrical properties is much improved. Mobility analysis shows that this excellent resistivity is mostly due to an increase in donor concentration, rather than a decrease in acceptor concentration. Optical …

Mobility Analysis Of Highly Conducting Thin Films: Application To Zno, David C. Look, K. D. Leedy, D. H. Tomich, B. Bayraktaroglu

Physics Faculty Publications

Hall-effect measurements have been performed on a series of highly conductive thin films of Ga-doped ZnO grown by pulsed laser deposition and annealed in a forming-gas atmosphere (5% H₂ in Ar). The mobility as a function of thickness d is analyzed by a simple formula involving only ionized-impurity and boundary scattering and having a single fitting parameter, the acceptor/donor concentration ratio K = N_A/N_D. For samples with d = 3–100 nm, K_avg = 0.41, giving N_D = 4.7×10²⁰ and N_A = 1.9×10²⁰ cm⁻³. Thicker samples require a …

Ferroelectric Phase Transitions In Three-Component Short-Period Superlattices Studied By Ultraviolet Raman Spectroscopy, Dmitri Tenne, H. N. Lee, R. S. Katiyar, X. X. Xi

Physics Faculty Publications and Presentations

Vibrational spectra of three-component BaTiO₃SrTiO₃CaTiO₃ short-period superlattices grown by pulsed laser deposition with atomic-layer control have been investigated by ultraviolet Raman spectroscopy. Monitoring the intensity of the first-order phonon peaks in Raman spectra as a function of temperature allowed determination of the ferroelectric phase transition temperature, T_c. Raman spectra indicate that all superlattices remain in the tetragonal ferroelectric phase with out-of-plane polarization in the entire temperature range below T_c. The dependence of T_c on the relative thicknesses of ferroelectric (BaTiO₃) to non-ferroelectric materials (SrTiO₃ and CaTiO_{3 …}

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 …

Measuring Dispersion In Laser Cavity Mirrors Using White-Light Interferometry, Allison S. Goodspeed

Theses and Dissertations

Terahertz radiation is an emerging field that has far reaching applications. There is a need for portable and affordable terahertz sources that may be used for detection of structural weaknesses in aerospace composites. One possibility for terahertz generation is a femtosecond Cr:LiSAF laser. However, controlling intracavity dispersion is necessary in order to get the ultrashort pulses needed to generate terahertz radiation. This research measures dispersion of the chirped femtosecond intracavity mirrors by employing white-light interferometry and explains the theory behind the curve-fitting process used to calculate dispersion. To compensate for the narrow reflectivity band of the mirrors, a CaF_{2 …}

Reproducible Increased Mg Incorporation And Large Hole Concentration In Gan Using Metal Modulated Epitaxy, Shawn D. Burnham, Gon Namkoong, David C. Look, Bruce Clafin, W. Alan Doolittle

Electrical & Computer Engineering Faculty Publications

The metal modulated epitaxy (MME) growth technique is reported as a reliable approach to obtain reproducible large hole concentrations in Mg-doped GaN grown by plasma-assisted molecular-beam epitaxy on c-plane sapphire substrates. An extremely Ga-rich flux was used, and modulated with the Mg source according to the MME growth technique. The shutter modulation approach of the MME technique allows optimal Mg surface coverage to build between MME cycles and Mg to incorporate at efficient levels in GaN films. The maximum sustained concentration of Mg obtained in GaN films using the MME technique was above 7 × 10²⁰ cm^{-3 …}

Activation Energy Of Surface Diffusion And Terrace Width Dynamics During The Growth Of In (4×3) On Si (100) - (2×1) By Femtosecond Pulsed Laser Deposition, M. A. Hafez, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The nucleation and growth of indium on a vicinal Si (100) - (2×1) surface at high temperature by femtosecond pulsed laser deposition was investigated by in situ reflection high energy electron diffraction (RHEED). RHEED intensity relaxation was observed for the first ∼2 ML during the growth of In (4×3) by step flow. From the temperature dependence of the rate of relaxation, an activation energy of 1.4±0.2 eV of surface diffusion was determined. The results indicate that indium small clusters diffused to terrace step edges with a diffusion frequency constant of (1.0±0.1) × 10¹¹ s^-1. The RHEED specular …

Near-Field Thermal Radiative Transfer And Thermoacoustic Effects From Vapor Plumes Produced By Pulsed Co/Sub 2 /Laser Ablation Of Bulk Water, S. I. Kudryashov, Kevin Lyon, S. D. Allen

Mechanical Engineering - Daytona Beach

Submillimeter deep heating of bulk water by thermal radiation from ablative water plumes produced by a 10.6 μm transversely excited atmospheric C O2 laser and the related acoustic generation has been studied using a contact time-resolved photoacoustic technique. Effective penetration depths of thermal radiation in water were measured as a function of incident laser fluence and the corresponding plume temperatures were estimated. The near-field thermal and thermoacoustic effects of thermal radiation in laser-ablated bulk water and their potential near-field implications are discussed.

c 2006 American Institute of Physics

Magnetic And Transport Properties Of Nimnal Thin Films, Andriy Vovk, Minghui Yu, Leszek Malkinski, Charles O'Connor, Zhenjun Wang, Eden Durant, Jinke Tang, Vladimir Golub

Physics Faculty Publications

The magnetic and transport properties of Ni₂MnAl thin films prepared using pulse laser deposition were investigated. It was shown that the films are granular and multiphase. Contrary to the data reported earlier we observe nonmonotonic temperature dependence of resistance with minimum in the vicinity of 100 K for the films deposited on substrates held at 773 K and negative magnetoresistance (MR) values of about 2.5% at 5 K and 1.6% at RT in magnetic field of 50 kOe. These values of MR are the highest reported up to date for Ni₂MnAl films. Large negative MR in …