Monte Carlo Study of Short-Range Order and Displacement Effects in Disordered CuAu

The correlation between local chemical environment and atomic displacements in disordered CuAu alloy has been studied using Monte Carlo simulations based on the effective medium theory (EMT) of metallic cohesion. These simulations correctly reproduce the chemically-specific nearest-neighbor distances in the random alloy across the entire Cu\$_x\$Au\$_{1-x}\$ concentration range. In the random equiatomic CuAu alloy, the chemically specific pair distances depend strongly on the local atomic environment (i.e. fraction of like/unlike nearest neighbors). In CuAu alloy with short-range order, the relationship between local environment and displacements remains qualitatively similar. However the increase in short-range order causes the average Cu-Au distance to decrease below the average Cu-Cu distance, as it does in the ordered CuAuI phase. Many of these trends can be understood qualitatively from the different neutral sphere radii and compressibilities of the Cu and Au atoms.Comment: 9 pages, 5 figures, 2 table

A scattering rate approach to the understanding of absorption line broadening in near-infrared AlGaN/GaN quantum wells

There has been much interest in the advancement of III-Nitride growth technology to fabricate AlGaN/GaN heterostructures for intersubband transitions (ISBTs). The large conduction band offset in these structures (up to 2 eV) allows transition energies in the near- to the far-infrared region, which have applications from telecommunications, such as in all-optical switches, to infra-red detectors for sensing and imaging. To date, ISBT electroluminescence has been elusive and absorption measurements remain an important method to verify band structure calculations. The growth quality can be inferred from the absorption spectrum, which will have line broadening with contributions that are both inhomogeneous (large-scale interface roughness, and non-parabolicity) and homogeneous (electron scattering related lifetime broadening). In the present work we calculated the contributions of various homogeneous broadening mechanisms (electron interaction with longitudinal-optical (LO) phonons, acoustic phonons, impurities and alloy disorder) to the full linewidth, and also the contribution of band non-parabolicity, which contributes to the inhomogeneous broadening. Calculations are then compared to the measured absorption spectra of several samples

Design considerations for GaN/AlN based unipolar (opto-)electronic devices, and interface quality aspects

We describe the theoretical and experimental studies of GaN/AlGaN based resonant tunnelling diodes, and in particular analyse the effects and typical values of interface roughness, and then discuss the implications of these, realistic material quality parameters on performance of unipolar optoelectronic devices

Coherent vertical electron transport and interface roughness effects in AlGaN/GaN intersubband devices

We investigate electron transport in epitaxially-grown nitride-based resonant tunneling diodes (RTDs) and superlattice sequential tunneling devices. A density-matrix model is developed, and shown to reproduce the experimentally measured features of the current–voltage curves, with its dephasing terms calculated from semi-classical scattering rates. Lifetime broadening effects are shown to have a significant influence in the experimental data. Additionally, it is shown that the interface roughness geometry has a large effect on current magnitude, peak-to-valley ratios and misalignment features; in some cases eliminating negative differential resistance entirely in RTDs. Sequential tunneling device characteristics are dominated by a parasitic current that is most likely to be caused by dislocations, however excellent agreement between the simulated and experimentally measured tunneling current magnitude and alignment bias is demonstrated. This analysis of the effects of scattering lifetimes, contact doping and growth quality on electron transport highlights critical optimization parameters for the development of III-nitride unipolar electronic and optoelectronic devices

Fabrication of high quality plan-view TEM specimens using the focused ion beam

We describe a technique using a focused ion beam instrument to fabricate high quality plan-view specimens for transmission electron microscopy studies. The technique is simple, site-specific and is capable of fabricating multiple large, >100 μm2 electron transparent windows within epitaxially-grown thin films. A film of La0.67Sr0.33MnO3 is used to demonstrate the technique and its structural and functional properties are surveyed by high resolution imaging, electron spectroscopy, atomic force microscopy and Lorentz electron microscopy. The window is demonstrated to have good thickness uniformity and a low defect density that does not impair the film’s Curie temperature. The technique will enable the study of in–plane structural and functional properties of a variety of epitaxial thin film systems

The Vehicle, Spring 1993

1993 Commemorative Edition: Celebrating 35 Years Table of Contents The Vehicle Editors\u27 Lineagepage 5 Milestonespage 6 THE SIXTIES Coverspage 7 Editors\u27 Notespage 8 Sureness is Never - excerptDon Shepardsonpage 9 SophisticationBenjamin Polkpage 10 A SonnetMignon Stricklandpage 11 The Twenty-Third ChannelBen Polkpage 11 Opposite AttractionsC.E.M. (Christine McColl)page 12 John F. KennedyJoel E. Hendrickspage 13 The Girl on the White PonyLarry Gatespage 14 The TimesW.D.M. (William Moser)page 16 Home ThoughtsJane Careypage 17 1966Roger Zulaufpage 18 Nagging ThoughtJanet Andrewspage 18 THE SEVENTIES Coverspage 19 Editors\u27 Notespage 20 RevolutionsSteve Siegelpage 21 UntitledKristine Kirkhampage 23 The Arithmetic ProblemJanice Forbuspage 23 Willie Seeverson Threw a Worm at MeMary Pipekpage 24 a love poem (by approximation)Ted Baldwinpage 25 Night and Summer in Two WorldsBarry Smithpage 26 Story of a Teenage PickleTerry Louis Schultzpage 27 Danny Lonely, Danny WildDevin Brownpage 28 Always TomorrowMary McDanielpage 29 THE EIGHTIES Coverspage 31 Having ChildrenDevon Flesorpage 33 What is Unnatural Is Sometimes MagicAngelique Jenningspage 34 If My Father Were A Writer, He Would Still BuildAngelique Jenningspage 35 Photo AlbumPatrick Peterspage 36 Poet Born in Pearl HarborAngelique Jenningspage 37 The History of High School BasketballPatrick Peterspage 38 Banana BreadGail Bowerpage 39 Cover LetterBob Zordanipage 40 Home MoviesBob Zordanipage 41 MigrationPatrick Peterspage 42 THE NINETIES Ba, Ba, Black SheepVictoria Bennettpage 45 Daily LessonsJennifer Moropage 49 Folding My OwnLaurie Ann Malispage 51 About the Authorspage 53 Editors\u27 Notespage 56https://thekeep.eiu.edu/vehicle/1062/thumbnail.jp

The Vehicle, Spring 1993

1993 Commemorative Edition: Celebrating 35 Years Table of Contents The Vehicle Editors\u27 Lineagepage 5 Milestonespage 6 THE SIXTIES Coverspage 7 Editors\u27 Notespage 8 Sureness is Never - excerptDon Shepardsonpage 9 SophisticationBenjamin Polkpage 10 A SonnetMignon Stricklandpage 11 The Twenty-Third ChannelBen Polkpage 11 Opposite AttractionsC.E.M. (Christine McColl)page 12 John F. KennedyJoel E. Hendrickspage 13 The Girl on the White PonyLarry Gatespage 14 The TimesW.D.M. (William Moser)page 16 Home ThoughtsJane Careypage 17 1966Roger Zulaufpage 18 Nagging ThoughtJanet Andrewspage 18 THE SEVENTIES Coverspage 19 Editors\u27 Notespage 20 RevolutionsSteve Siegelpage 21 UntitledKristine Kirkhampage 23 The Arithmetic ProblemJanice Forbuspage 23 Willie Seeverson Threw a Worm at MeMary Pipekpage 24 a love poem (by approximation)Ted Baldwinpage 25 Night and Summer in Two WorldsBarry Smithpage 26 Story of a Teenage PickleTerry Louis Schultzpage 27 Danny Lonely, Danny WildDevin Brownpage 28 Always TomorrowMary McDanielpage 29 THE EIGHTIES Coverspage 31 Having ChildrenDevon Flesorpage 33 What is Unnatural Is Sometimes MagicAngelique Jenningspage 34 If My Father Were A Writer, He Would Still BuildAngelique Jenningspage 35 Photo AlbumPatrick Peterspage 36 Poet Born in Pearl HarborAngelique Jenningspage 37 The History of High School BasketballPatrick Peterspage 38 Banana BreadGail Bowerpage 39 Cover LetterBob Zordanipage 40 Home MoviesBob Zordanipage 41 MigrationPatrick Peterspage 42 THE NINETIES Ba, Ba, Black SheepVictoria Bennettpage 45 Daily LessonsJennifer Moropage 49 Folding My OwnLaurie Ann Malispage 51 About the Authorspage 53 Editors\u27 Notespage 56https://thekeep.eiu.edu/vehicle/1062/thumbnail.jp