Engineering Commons^™

Anomalous Stranski-Krastanov Growth Of (111)-Oriented Quantum Dots With Tunable Wetting Layer Thickness, Christopher F. Schuck, Simon K. Roy, Trent Garrett, Paul J. Simmonds

Materials Science and Engineering Faculty Publications and Presentations

Driven by tensile strain, GaAs quantum dots (QDs) self-assemble on In_0.52Al_0.48As(111)A surfaces lattice-matched to InP substrates. In this study, we show that the tensile-strained self-assembly process for these GaAs(111)A QDs unexpectedly deviates from the well-known Stranski-Krastanov (SK) growth mode. Traditionally, QDs formed via the SK growth mode form on top of a flat wetting layer (WL) whose thickness is fixed. The inability to tune WL thickness has inhibited researchers’ attempts to fully control QD-WL interactions in these hybrid 0D-2D quantum systems. In contrast, using microscopy, spectroscopy, and computational modeling, we demonstrate that for GaAs(111)A QDs, we …

Machine Learning Predictions Electronic Couplings For Charge Transport Calculations Of P3ht, Evan D. Miller, Matthew L. Jones, Mike M. Henry, Bryan Stanfill, Eric Jankowski

Materials Science and Engineering Faculty Publications and Presentations

The purpose of this work is to lower the computational cost of predicting charge mobilities in organic semiconductors, which will benefit the screening of candidates for inexpensive solar power generation. We characterize efforts to minimize the number of expensive quantum chemical calculations we perform by training machines to predict electronic couplings between monomers of poly-(3-hexylthiophene). We test five machine learning techniques and identify random forests as the most accurate, information-dense, and easy-to-implement approach for this problem, achieving mean-absolute-error of 0.02 [× 1.6 × 10⁻¹⁹ J], R² = 0.986, predicting electronic couplings 390 times faster than quantum chemical calculations, …

Characterization Of Zirconium Oxides Part I: Raman Mapping And Spectral Feature Analysis, Corey M. Efaw, Jordan L. Vandegrift, Michael Reynolds, Samuel Mcmurdie, Brian J. Jaques, Hui Xiong, Michael F. Hurley

Materials Science and Engineering Faculty Publications and Presentations

Raman mapping of sectioned zirconium cladding oxides was performed to analyze different spectral features before and after breakaway, as well as between zirconium and its alloys Zr-2.65Nb, Zry-3, and Zry-4. Oxide phase composition, or percent tetragonality, was defined to compare tetragonal to monoclinic zirconia. Percent tetragonality was spatially mapped to support distinction of zirconia phase distribution. A tetragonal-rich layer was seen at the metal/oxide interface, while post-breakaway samples exhibited increased amount of tetragonal phase in the bulk of their oxides. Spatial mapping of spectral peak location and half-width at half-maximum was accomplished to distinguish differences in stability mechanisms of tetragonal-rich …

Oxidation Behavior Of Welded Zry-3, Zry-4, And Zr–1nb Tubes, Jordan Vandegrift, Clemente J. Parga, Ben Coryell, Darryl P. Butt, Brian J. Jaques

Materials Science and Engineering Faculty Publications and Presentations

The Transient Reactor Test (TREAT) facility is a research reactor designed to simulate rapid transients to test new fuel designs. TREAT's cladding is exposed to unique conditions compared to normal water reactors. These conditions include: exposure to air at high temperatures (≥600 °C), rapid heating (≈700 °^C/_s), and cladding geometry that includes chamfers and welds. This work investigates the effects of chamfering and welding on the oxidation behavior of zirconium alloys (Zircaloy-3, Zircaloy-4, and Zr–1Nb). Tube specimens were examined under isothermal and transient conditions in dry and humid air. The effect of weld type (tungsten inert …

Inas(111)A Homoepitaxy With Molecular Beam Epitaxy, Kevin D. Vallejo, Trent A. Garrett, Kathryn E. Sautter, Kevin Saythavy, Baolai Liang, Paul J. Simmonds

Materials Science and Engineering Faculty Publications and Presentations

The authors have established a robust set of growth conditions for homoepitaxy of high-quality InAs with a (111)A crystallographic orientation by molecular beam epitaxy (MBE). By tuning the substrate temperature, the authors obtain a transition from a 2D island growth mode to step-flow growth. Optimized MBE parameters (substrate temperature = 500 °C, growth rate = 0.12ML/s, and V/III ratio ≥ 40) lead to the growth of extremely smooth InAs(111)A films, free from hillocks and other 3D surface imperfections. The authors see a correlation between InAs surface smoothness and optical quality, as measured by photoluminescence spectroscopy. This work establishes InAs(111)A as …

A Parametric Study For In-Pile Use Of The Thermal Conductivity Needle Probe Using A Transient, Multilayered Analytical Model, Courtney Hollar, Austin Fleming, Kurt Davis, Ralph Budwig, Colby Jensen, David Estrada

Materials Science and Engineering Faculty Publications and Presentations

By utilizing an in-pile measurement, thermal conductivity can be determined under prototypic conditions over a range of burnup. In this work we develop a multilayer quadrupoles analytical model to describe the transient thermal interactions between a line heat source (i.e. needle probe) and cylindrical nuclear fuel geometry for inpile thermal conductivity measurements. A finite element analysis of the detailed needle probe geometry was compared to results from the analytical model to verify the assumptions made in the analytical model. Experimentally, the needle probe was used to measure the thermal properties of polytetrafluoroethylene (PTFE) and stainless steel 304 with three different …

Utilizing A Single Silica Nanospring As An Insulating Support To Characterize The Electrical Transport And Morphology Of Nanocrystalline Graphite, David Estrada, Paul H. Davis, Twinkle Pandhi

Materials Science and Engineering Faculty Publications and Presentations

A graphitic carbon, referred to as graphite from the University of Idaho thermolyzed asphalt reaction (GUITAR), was coated in silica nanosprings and silicon substrates via the pyrolysis of commercial roofing tar at 800 °C in an inert atmosphere. Scanning electron microscopy and transmission electron microscopy images indicate that GUITAR is an agglomeration of carbon nanospheres formed by the accretion of graphitic flakes into a ~100 nm layer. Raman spectroscopic analyses, in conjunction with scanning electron microscopy and transmission electron microscopy, indicate that GUITAR has a nanocrystalline structure consisting of ~1–5 nm graphitic flakes interconnected by amorphous sp³ bonded carbon. …

A Simple Method To Characterize High Rate Twin Boundary Kinetics In Ni-Mn-Ga, Bibek Karki, Peter Müllner

Materials Science and Engineering Faculty Publications and Presentations

Experimental characterization of twin boundary kinetics is essential to systematically test and reproduce the actuation properties of Magnetic Shape Memory (MSM) elements at high rates. Here, we present a simple, nondestructive, experimental method to quantify the dynamic response of an MSM crystal and extract the major material properties that govern its kinetics. The tested sample is subjected to a mechanical pulse that is produced by a simple off-the-shelf solenoid. The mechanical pulse leads to actuation of the tested MSM Ni–Mn–Ga single crystal within 10 ms, during which the twin boundary velocity varies between zero and 2 m/s. The displacement and …

Implementing Population-Based Mass Drug Administration For Malaria: Experience From A High Transmission Setting In North Eastern Uganda, Richard Elliott

Materials Science and Engineering Faculty Publications and Presentations

Background: Mass drug administration (MDA) is a suggested mean to accelerate efforts towards elimination and attainment of malaria-free status. There is limited evidence of suitable methods of implementing MDA programme to achieve a high coverage and compliance in low-income countries. The objective of this paper is to assess the impact of this MDA delivery strategy while using coverage measured as effective population in the community and population available.

Methods: Population-based MDA was implemented as a part of a larger program in a high transmission setting in Uganda. Four rounds of interventions were implemented over a period of 2 years at …

Oxidation Behavior Of Zirconium, Zircaloy-3, Zircaloy-4, Zr-1nb, And Zr- 2.5nb In Air And Oxygen, Jordan L. Vandegrift, Patrick M. Price, John-Paul Stroud, Clemente J. Parga, Isabella J. Van Rooyen, Brian J. Jaques, Darryl P. Butt

Materials Science and Engineering Faculty Publications and Presentations

The Transient Reactor Test (TREAT) facility at the Idaho National Laboratory currently utilizes a legacy Zircaloy- 3 cladding, which is no longer commercially available. TREAT is air cooled and routinely operates at temperatures well above that of traditional reactor designs. This study investigates the oxidation behavior of pure zirconium and its alloys (Zircaloy-3, Zircaloy-4, Zr-1Nb, Zr-2.5Nb) in Ar+20%O₂ and N₂+20%O₂ atmospheres at temperatures ranging from 400–800 °C to determine which alloy should be implemented as TREAT's cladding. While the oxidation behavior of zirconium based cladding materials has been extensively documented, this study focuses on direct comparison …

Lessons Learned About Building An Assertive Community, Donna C. Llewellyn, William L. Hughes, Megan F. Gambs

Materials Science and Engineering Faculty Publications and Presentations

One of our observations in this lessons learned paper is that there is underwhelming faculty development related to scholarship other than on how to submit and sometimes how to write proposals. This de facto service model misses everything outside of the proposal-writing process; which is the least important, but is often the most celebrated, rewarded, and supported phase. Inspired by national Centers for Teaching & Learning, and modeled after the emerging Communities of Transformation literature, we are piloting a Center for Transformative Research at Boise State University. The vision of our Center is to build and sustain an ASSERTive community …

Voices Of Our Students: Using Evidence-Based Methods To Inform A Multidisciplinary Engineering Program Design, Vicki Stieha, Noah Salzman, Amy J. Moll

Materials Science and Engineering Faculty Publications and Presentations

Listening carefully to our students and integrating the variables that matter to them is a step that we can take to increase the number of women and underrepresented minority graduates in engineering. This paper shares an evaluative case study as we report findings from data gathering tools guiding our continuous improvement process. The findings illuminate students’ perceptions of their engineering design course and curriculum. We conclude by discussing the pedagogical decisions the teaching team is making as a result of listening to our students’ voices.

Synergy And Timing: A Concurrent Mass Medical Campaign Predicted To Augment Indoor Residual Spraying For Malaria, Richard C. Elliott, David L. Smith, Dorothy C. Echodu

Materials Science and Engineering Faculty Publications and Presentations

Background: Control programmes for high burden countries are tasked with charting effective multi-year strategies for malaria control within significant resource constraints. Synergies between different control tools, in which more than additive benefit accrues from interventions used together, are of interest because they may be used to obtain savings or to maximize health impact per expenditure. One commonly used intervention in sub-Saharan Africa is indoor residual spraying (IRS), typically deployed through a mass campaign. While possible synergies between IRS and long-lasting insecticide-treated nets (LLINs) have been investigated in multiple transmission settings, coordinated synergy between IRS and other mass medical distribution campaigns …

Thermal Transport In Layer-By-Layer Assembled Polycrystalline Graphene Films, David Estrada, Alondra Perez

Materials Science and Engineering Faculty Publications and Presentations

New technologies are emerging which allow us to manipulate and assemble 2-dimensional (2D) building blocks, such as graphene, into synthetic van der Waals (vdW) solids. Assembly of such vdW solids has enabled novel electronic devices and could lead to control over anisotropic thermal properties through tuning of inter-layer coupling and phonon scattering. Here we report the systematic control of heat flow in graphene-based vdW solids assembled in a layer-by-layer (LBL) fashion. In-plane thermal measurements (between 100 K and 400 K) reveal substrate and grain boundary scattering limit thermal transport in vdW solids composed of one to four transferred layers of …

Corrosion Initiation And Propagation On Carburized Martensitic Stainless Steel Surfaces Studied Via Advanced Scanning Probe Microscopy, Armen Kvryan, Corey M. Efaw, Kari A. Higginbotham, Olivia O. Maryon, Paul H. Davis, Elton Graugnard, Michael F. Hurley

Materials Science and Engineering Faculty Publications and Presentations

Historically, high carbon steels have been used in mechanical applications because their high surface hardness contributes to excellent wear performance. However, in aggressive environments, current bearing steels exhibit insufficient corrosion resistance. Martensitic stainless steels are attractive for bearing applications due to their high corrosion resistance and ability to be surface hardened via carburizing heat treatments. Here three different carburizing heat treatments were applied to UNS S42670: a high-temperature temper (HTT), a low-temperature temper (LTT), and carbo-nitriding (CN). Magnetic force microscopy showed differences in magnetic domains between the matrix and carbides, while scanning Kelvin probe force microscopy (SKPFM) revealed a 90–200 …

Roadmap On Biological Pathways For Electronic Nanofabrication And Materials, Reza M. Zadegan

Materials Science and Engineering Faculty Publications and Presentations

Conventional microchip fabrication is energy and resource intensive. Thus, the discovery of new manufacturing approaches that reduce these expenditures would be highly beneficial to the semiconductor industry. In comparison, living systems construct complex nanometer-scale structures with high yields and low energy utilization. Combining the capabilities of living systems with synthetic DNA-/protein-based self-assembly may offer intriguing potential for revolutionizing the synthesis of complex sub-10 nm information processing architectures. The successful discovery of new biologically based paradigms would not only help extend the current semiconductor technology roadmap, but also offer additional potential growth areas in biology, medicine, agriculture and sustainability for the …

Open-Source Automated Chemical Vapor Deposition System For The Production Of Two-Dimensional Nanomaterials, Lizandra Williams-Godwin, Dale Brown, Richard Livingston, Tyler Webb, Lynn Karriem, Elton Graugnard, David Estrada

Materials Science and Engineering Faculty Publications and Presentations

The study of two- dimensional (2D) materials is a rapidly growing area within nanomaterials research. However, the high equipment costs, which include the processing systems necessary for creating these materials, can be a barrier to entry for some researchers interested in studying these novel materials. Such process systems include those used for chemical vapor deposition, a preferred method for making these materials. To address this challenge, this article presents the first open-source design for an automated chemical vapor deposition system that can be built for less than a third of the cost for a comparable commercial system. The materials and …

Toward Improving Ambient Volta Potential Measurements With Skpfm For Corrosion Studies, Corey M. Efaw, Thiago Da Silva, Paul H. Davis, Lan Li, Elton Graugnard, Michael F. Hurley

Materials Science and Engineering Faculty Publications and Presentations

Scanning Kelvin probe force microscopy (SKPFM) is used in corrosion studies to quantify the relative nobility of different microstructural features present within complex metallic systems and thereby elucidate possible corrosion initiation sites. However, Volta potential differences (VPDs) measured via SKPFM in the literature for metal alloys exhibit large variability, making interpretation and application for corrosion studies difficult. We have developed an improved method for referencing SKPFM VPDs by quantifying the closely related work function of the probe relative to an inert gold standard whose modified work function is calculated via density functional theory (DFT). By measuring and tracking changes in …

Fabrication Of Stoichiometric U3Si2 Fuel Pellets, Adrian R. Wagner, Jason M. Harp, Kip E. Archibald, Seth C. Ashby, Jennifer K. Watkins, Kevin R. Tolman

Materials Science and Engineering Faculty Publications and Presentations

Uranium silicide, U₃Si₂, is an accident tolerant fuel type which is gaining momentum as a replacement fuel for uranium dioxide (UO₂). Idaho National Laboratories has been fabricating phase pure U₃Si₂ fuel pellets for use in various irradiation and material characterization experiments. Stoichiometric U₃Si₂ fuel pellets were fabricated using a powder metallurgy and arcmelting technique. The use of the stoichiometric ratio to alloy uranium and silicon, and sintering in a vacuum environment allowed for the fabrication of high density (>94% theoretical density), phase pure pellets, greater than 94% …