Materials Science and Engineering Commons^™

Electronically Enhanced Surface Diffusion During Ge Growth On Si(100), Ali Orguz Er, Hani E. Elsayed-Ali

Physics Faculty Publications

The effect of nanosecond pulsed laser excitation on surface diffusion during the growth of Ge on Si(100) at 250 °C was studied. In situ reflection high-energy electron diffraction was used to measure the surface diffusion coefficient while ex situ atomic force microscopy was used to probe the structure and morphology of the grown quantum dots. The results show that laser excitation of the substrate increases the surface diffusion during the growth of Ge on Si(100), changes the growth morphology, improves the crystalline structure of the grown quantum dots, and decreases their size distribution. A purely electronic mechanism of enhanced surface …

Nonuniformity In Lattice Contraction Of Bismuth Nanoclusters Heated Near Its Melting Point, A. Esmail, M. Abdel-Fattah, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The structural properties of bismuth nanoclusters were investigated with transmission high-energy electron diffraction from room temperature up to 525 ± 6 K. The Bi nanoclusters were fabricated by thermal evaporation at room temperature on transmission electron microscope grids coated with an ultrathin carbon film, followed by thermal and femtosecond laser annealing. The annealed sample had an average cluster size of ∼14 nm along the minor axis and ∼16 nm along the major axis. The Debye temperature of the annealed nanoclusters was found to be 53 ± 6 K along the [012] direction and 86 ± 9 K along the [110] …

Low Temperature Epitaxial Growth Of Ge Quantum Dot On Si (100) - (2×1) By Femtosecond Laser Excitation, Ali Oguz Er, Wei Ren, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Low temperature epitaxy of Ge quantum dots on Si (100) - (2×1) by femtosecond pulsed laser deposition under femtosecond laser excitation was investigated. Reflection high-energy electron diffraction and atomic force microscopy were used to analyze the growth mode and morphology. Epitaxial growth was achieved at ∼70 °C by using femtosecond laser excitation of the substrate. A purely electronic mechanism of enhanced surface diffusion of the Ge adatoms is proposed. © 2011 American Institute of Physics. [doi:10.1063/1.3537813]

Precise Control Of Highly Ordered Arrays Of Nested Semiconductor/Metal Nanotubes, Diefeng Gu, Helmut Baumgart, Kandabara Tapily, Pragya Shrestha, Gon Namkoong, Xianyu Ao, Frank Müller

Electrical & Computer Engineering Faculty Publications

Lithographically defined microporous templates in conjunction with the atomic layer deposition (ALD) technique enable remarkable control of complex novel nested nanotube structures. So far three-dimensional control of physical process parameters has not been fully realized with high precision resolution, and requires optimization in order to achieve a wider range of potential applications. Furthermore, the combination of composite insulating oxide layers alternating with semiconducting layers and metals can provide various types of novel applications and eventually provide unique and advanced levels of multifunctional nanoscale devices. Semiconducting TiO₂ nanotubes have potential applications in photovoltaic devices. The combination of nanostructured semiconducting materials …

Growth And Characterization Of Nanoscale Thin Films, Erik Thomas Wolter

Honors Program Theses

Thin manganese films were grown by thermal evaporation in high vacuum. The growth rate was varied to determine how the growth rate affects the continuity of ultra-thin films. The resistance was measured with the two-point method in situ and the data was recorded digitally. The resistance was converted to resistivity and this was plotted against thickness. It was found that resistivity decreases exponentially as the film begins to form in islands. The film reaches a critical thickness as the islands coalesce and the data can then be fitted with Fuchs’ equation. The resistivity continues to decrease but the minimum resistivity …

Modelling Of Low Velocity Impact Of Laminated Composite Substructures, Homayoun Hadavinia, Fatih Dogan, Ahmed M. Elmarakbi, Seyed Mohammad Reza Khalili

Materials Science and Engineering Faculty Research & Creative Works

Impact is among the important loading scenario which is required to be addressed for fibre reinforced plastics (FRP) materials in ground or space vehicle applications. The failure behaviour of FRP materials under impact loading is a complex process and a detailed analysis of various mode of failure is necessary. In this paper the failure behaviour of laminated carbon fibre reinforced plastic (CFRP) composite structures under impact loading is investigated by conducting numerical simulations using the explicit finite element analysis ANSYS LS-DYNA software [1]. The impact responses and failure behaviours are being investigated by performing a parametric study and sensitivity analysis …

Direct Femtosecond Laser Waveguide Writing Inside Zinc Phosphate Glass, Luke B. Fletcher, Jon J. Witcher, Neil Troy, Signo Tadeu Dos Reis, Richard K. Brow, Denise M. Krol

Materials Science and Engineering Faculty Research & Creative Works

We report the relationship between the initial glass composition and the resulting microstructural changes after direct femtosecond laser waveguide writing with a 1 kHz repetition rate Ti:sapphire laser system. A zinc polyphosphate glass composition with an oxygen to phosphorus ratio of 3.25 has demonstrated positive refractive index changes induced inside the focal volume of a focusing microscope objective for laser pulse energies that can achieve intensities above the modification threshold. The permanent photo-induced changes can be used for direct fabrication of optical waveguides using single scan writing techniques. Changes to the localized glass network structure that produce positive changes in …

Femtosecond Laser Writing Of Waveguides In Zinc Phosphate Glasses [Invited], Luke B. Fletcher, Jon J. Witcher, Neil Troy, Signo Tadeu Dos Reis, Richard K. Brow, R. M. Vazquez, R. Osellame, Denise M. Krol

Materials Science and Engineering Faculty Research & Creative Works

We have studied the relationship between the initial glass composition and the structural changes associated with laser-induced refractive index modification in a series of Er-Yb doped and undoped zinc phosphate glasses. White light microscopy and waveguide experiments are used together with Raman and fluorescence spectroscopy to characterize the structural changes. The correlation between Raman peak shifts and fluorescence from phosphorus-oxygen hole center (POHC) defects indicates that fs-laser writing results in a depolymerization of the phosphate glass network. The results also show that the exact glass composition should be taken into account when fabricating waveguide devices in phosphate glasses, in order …

Stress Measurement And Development Of Zirconium Diboride-Silicon Carbide Ceramics, Jeremy Lee Watts

Doctoral Dissertations

"Research presented in this dissertation focused on the production of ZrB₂-SiC composites and their characterization; in particular their mechanical properties and thermally generated residual stresses. Thermally generated stresses were measured using Raman spectroscopy as well as both neutron and x-ray diffraction. For 70 vol% ZrB₂ - 30 vol% SiC composites neutron diffraction revealed that the SiC phase was under ~880 MPa compressive stress and the ZrB₂ phase was under ~450 MPa tension at room temperature. It was also discovered that stresses began to accumulate at ~1400 ⁰C upon cooling from the processing temperature (1900 ⁰C -2000 ⁰C). Raman spectroscopy and …

Two-Point Bend Studies Of Glass Fibers, Zhongzhi Tang

Doctoral Dissertations

"The principal objective of this research is to advance our understanding of how glass breaks. Glass, a material well known for its brittleness, has been used widely but within a frustrating limit of its strength. Generally, strength is not considered as an intrinsic property of glass, due to the difficulty of avoiding the presence of flaws on the sample surface. The fiber drawing system and two-point bending (TPB) equipment developed at Missouri S&T allow the fabrication of pristine glass fibers and failure strain measurements while minimizing the effects of strength limiting critical flaws. Several conditions affect the failure behavior of …

Alloy Dissolution In Argon Stirred Steel, Darryl S. Webber

Doctoral Dissertations

"Alloying is required for the production of all steel products from small castings to large beams. Addition of large quantities of bulk alloys can result in alloy segregation and inconsistent alloy recovery. The objective of this research was to better understand alloy dissolution in liquid steel especially as it relates to Missouri S&Ts' patented continuous steelmaking process. A 45-kilogram capacity ladle with a single porous plug was used to evaluate the effect of four experimental factors on alloy dissolution: alloy species, alloy size or form, argon flow rate, and furnace tap temperature. Four alloys were tested experimentally including Class I …

Characterization Of Rf Resonators Made Of Biodegradable Materials For Biosensing Applications, Clémentine M. Boutry, Hengky Chandrahalim, Christofer Hierold

Faculty Publications

In this paper we present the characterization by galvanic coupling (direct contact) of radio-frequency (RF) driven RLC resonators made of different biodegradable materials, including biodegradable metals and new biodegradable conducting polymers. An equivalent electrical circuit is proposed based on the RLC resonator geometry and material properties. The Matlab modeling and the finite elements HFSS simulations are in good agreement with the measurements, and allow to extract the loaded and unloaded parameters of the RLC resonators for different materials.

Ammoniacal Thiosulphate Leaching Of A Copper-Rich Gold Ore, Ahmet Deniz Bas, Elif Ozdemir, Ersin Y. Yazici, Oktay Celep, Haci Deveci

Ahmet Deniz Bas

No abstract provided.

Issues Of Wind Power For Renewable Society Construction At 3-11 Earthquake & Tsunami Striken Areas 被災地からの自然エネルギー社会づくりと風力発電の課題, Masayuki Horio

Masayuki Horio

No abstract provided.

The Analysis Of The Tribological Properties Of Multiple Strengthened Nanocomposite Of The Cu-Al2o3 System, Zeljko J. Kamberovic

Zeljko J Kamberovic

This paper presents the results of examined tribological properties of the multiple strengthened nanocomposite Cu-Al2O3 system. Cu-Al2O3 composite powder was obtained by combination of the thermo-chemical procedure and mechanical alloying, which is a completely new approach to synthesis of these materials. The synthesized powders were cold pressed with 940MPa and sintered in hydrogen atmosphere in temperature range of 725-925o C during 15-120 minutes. The samples were thermo- mechanically treated in two stages after sintering: cold rolling with the final reduction degree of 30% and annealing at 800o C for 1h in hydrogen atmosphere. Characterization of the sintered, rolled and annealed …

Reverse Logic - Safety Of Spent Nuclear Fuel Disposal, Antti Lempinen, Marianne Silvan-Lempinen

Antti Lempinen

No abstract provided.

Determination Of Color Stability In Electrophotographic Digital Printing Systems, S. Kocabey, T. Sahinbaskan, Bilge N. Altay

Bilge Nazli Altay

Analyzing The Relation Between Optical Properties Of Substrates Used For Electrophotographic Printing System And Their Color Gamut Reproduction, Bilge N. Altay, T. Sahinbaskan

Bilge Nazli Altay

Critical Analysis On The Structural And Magnetic Properties Of Bulk And Nanocrystalline Cu-Fe-O, D. Paul Joseph, C. Venkateswaran, R. Selva Vennila

Center for Study of Matter at Extreme Conditions

Nanocrystalline and bulk samples of “Fe”-doped CuO were prepared by coprecipitation and ceramic methods. Structural and compositional analyses were performed using X-ray diffraction, SEM, and EDAX. Traces of secondary phases such as CuFe₂O₄, Fe₃O₄, and α-Fe₂O₃ having peaks very close to that of the host CuO were identified from the Rietveld profile analysis and the SAED pattern of bulk and nanocrystalline Cu_0.98Fe_0.02O samples. Vibrating Sample Magnetometer (VSM) measurements show hysteresis at 300 K for all the samples. The ferrimagnetic Neel transition temperature () was found …

Self-Pulsing And Chaos In Distributed Feedback Bistable Optical Devices, Herbert G. Winful, Gene D. Cooperman

Gene D. Cooperman

We show that the light transmitted by a nonlinear distributed feedback structure can be steady (time independent), periodic, or chaotic depending on the intensity of the input cw beam. The feasibility of an experimental demonstration of such behavior is discussed.