Secondary ion mass spectrometry of vapor−liquid−solid grown, Au-catalyzed, Si wires

Knowledge of the catalyst concentration within vapor-liquid-solid (VLS) grown semiconductor wires is needed in order to assess potential limits to electrical and optical device performance imposed by the VLS growth mechanism. We report herein the use of secondary ion mass spectrometry to characterize the Au catalyst concentration within individual, VLS-grown, Si wires. For Si wires grown by chemical vapor deposition from SiCl_4 at 1000 °C, an upper limit on the bulk Au concentration was observed to be 1.7 x 10^16 atoms/cm^3, similar to the thermodynamic equilibrium concentration at the growth temperature. However, a higher concentration of Au was observed on the sidewalls of the wires

Comparative study of dimer vacancies and dimer-vacancy lines on Si(001) and Ge(001)

Although the clean Si(001) and Ge(001) surfaces are very similar, experiments to date have shown that dimer-vacancy (DV) defects self-organize into vacancy lines (VLs) on Si(001), but not on Ge(001). In this paper, we perform empirical-potential calculations aimed at understanding the differences between the vacancies on Si(001) and Ge(001). We identify three energetic parameters that characterize the DVs on the two surfaces: the formation energy of a single DV, the attraction between two DVs in adjacent dimer rows, and the strain sensitivity of the formation energy of DVs and VLs. At the empirical level of treatment of the atomic interactions (Tersoff potentials), all three parameters are favorable for the self-assembly of DVs on the Si(001) surface rather than on Ge(001). The most significant difference between the defects on Si(001) and on Ge(001) concerns the formation energy of single DVs, which is three times larger in the latter case. By calculating the strain-dependent formation energies of DVs and VLs, we propose that the experimental observation of self-assembly of vacancies on clean Ge(001) could be achieved by applying compressive strains of the order of 2%.Comment: 3 tables, 4 figures, to appear in Surface Scienc

Explicit Instruction of Memory Vocabulary Learning Strategies in an ESP Context

Recent studies have shown that proficient language learners make substantial use of vocabulary learning strategies (VLS). However, teaching VLS is not emphasized in English education in Japan. This is especially problematic when students are required to learn the technical terms of their field in university since those terms are usually low-frequency words that the students do not encounter when learning academic English. The present study examines the effectiveness of explicit VLS instruction for learning biology terms for Japanese students who major in biology. The study also investigates which VLS are suitable for these students in accordance with their vocabulary size. The instructed VLS in this study were all memory strategies: imagery, association, grouping, and a strategy using affixes. The results revealed that both students with smaller vocabulary sizes and those with larger vocabulary sizes were satisfied with explicit VLS instruction but that lack of vocabulary can hinder the use of some types of memory strategies. The study demonstrates the efficacy of explicit memory VLS instruction in ESP settings, especially the strategy using affixes and roots

The University of Nebraska does not discriminate based on race, color, ethnicity, national origin, sex, pregnancy, sexual orientation, gender identity, religion, disability, age, genetic information, veteran status, marital status, and/or political affiliation in its education programs or activities, including admissions and employment. The University prohibits any form of retaliation taken against anyone for reporting discrimination, harassment, or retaliation for otherwise engaging in protected activity. Understanding Volunteerism in Vocational and Life Skills Programming

The purpose of this research is to understand who volunteers for Vocational & Life Skills (VLS) reentry programming in institutional and community correctional settings. We had three primary goals for this research note: 1) describe key differences between participants versus non-participants, 2) describe how VLS participants in facilities differ from participants in community VLS programs, and 3) describe key findings from our statistical models predicting who volunteers to participate in VLS programs. VLS is a statewide reentry program that provides competitive grant funding to multiple community resource organizations and is administered by the Nebraska Department of Correctional Services (NDCS). VLS grantees provide services that include prerelease counseling, case management, educational courses, and training in specific trades

A Note on Alternating Minimization Algorithm for the Matrix Completion Problem

We consider the problem of reconstructing a low rank matrix from a subset of its entries and analyze two variants of the so-called Alternating Minimization algorithm, which has been proposed in the past. We establish that when the underlying matrix has rank $r=1$, has positive bounded entries, and the graph $\mathcal{G}$ underlying the revealed entries has bounded degree and diameter which is at most logarithmic in the size of the matrix, both algorithms succeed in reconstructing the matrix approximately in polynomial time starting from an arbitrary initialization. We further provide simulation results which suggest that the second algorithm which is based on the message passing type updates, performs significantly better.Comment: 8 pages, 2 figure

Vortex Lattice Structure of Fulde-Ferrell-Larkin-Ovchinnikov Superconductors

In superconductors with singlet pairing, the inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is expected to be stabilized by a large Zeeman splitting. We develop an efficient method to evaluate the Landau-Ginzburg free energies of FFLO-state vortex lattices and use it to simplify the considerations that determine the optimal vortex configuration at different points in the phasediagram. We demonstrate that the order parameter spatial profile is completely determined, up to a uniform translation, by its Landau level index n and the vortex Lattice structure and derive an explicit expression for the order parameter spatial profile that can be used to determine n from experimental data.Comment: 6 pages with one embedded color figure. Minor changes. Final version as publishe