Vacancy complexes in nonequilibrium germanium-tin semiconductors

Understanding the nature and behavior of vacancy-like defects in epitaxial GeSn metastable alloys is crucial to elucidate the structural and optoelectronic properties of these emerging semiconductors. The formation of vacancies and their complexes is expected to be promoted by the relatively low substrate temperature required for the epitaxial growth of GeSn layers with Sn contents significantly above the equilibrium solubility of 1 at.%. These defects can impact both the microstructure and charge carrier lifetime. Herein, to identify the vacancy-related complexes and probe their evolution as a function of Sn content, depth-profiled pulsed low-energy positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy were combined to investigate GeSn epitaxial layers with Sn content in the 6.5-13.0 at.% range. The samples were grown by chemical vapor deposition method at temperatures between 300 and 330 {\deg}C. Regardless of the Sn content, all GeSn samples showed the same depth-dependent increase in the positron annihilation line broadening parameters, which confirmed the presence of open volume defects. The measured average positron lifetimes were the highest (380-395 ps) in the region near the surface and monotonically decrease across the analyzed thickness, but remain above 350 ps. All GeSn layers exhibit lifetimes that are 85 to 110 ps higher than the Ge reference layers. Surprisingly, these lifetimes were found to decrease as Sn content increases in GeSn layers. These measurements indicate that divacancies are the dominant defect in the as-grown GeSn layers. However, their corresponding lifetime was found to be shorter than in epitaxial Ge thus suggesting that the presence of Sn may alter the structure of divacancies. Additionally, GeSn layers were found to also contain a small fraction of vacancy clusters, which become less important as Sn content increases

Control of interlayer exchange coupling in Fe/Cr/Fe trilayers by ion beam irradiation

The manipulation of the antiferromagnetic interlayer coupling in the epitaxial Fe/Cr/Fe(001) trilayer system by moderate 5 keV He ion beam irradiation has been investigated experimentally. It is shown that even for irradiation with very low fluences (10^14 ions/cm^2) a drastic change in strength of the coupling appears. For thin Cr-spacers (below 0.6 - 0.7 nm) the coupling strength decreases with fluence, becoming ferromagnetic for fluences above (2x10^14 ions/cm^2). The effect is connected with the creation of magnetic bridges in the layered system due to atomic exchange events caused by the bombardment. For thicker Cr spacers (0.8 - 1.2 nm) an enhancement of the antiferromagnetic coupling strength is found. A possible explanation of the enhancement effect is given.Comment: Submitted to PR

Особенности аннигиляции позитронов в наноразмерных металлических слоях Zr/Nb после облучения ионами He+

Новые технологии получения конструкционных материалов, устойчивых к водородным и радиационным повреждениям, являются актуальными проблемами материаловедения. Водородное повреждение и радиационная деградация являются важными факторами, ограничивающими усталостную долговечность конструкционных материалов. Одной из перспективных альтернатив при разработке радиационно-водородостойких материалов с улучшенными физико-механическими свойствами является нанесение наноразмерных металлических покрытий (НМП). Настоящая работа посвящена изучению аннигиляции позитронов в НМП Zr/Nb с различной толщиной отдельных слоев Zr и Nb после облучения ионами He+ с дозами от 3⸱1016 ионов/см2 до 3⸱1017 ионов/см2

O Imaginário de Porto Alegre por seus cartões-postais

This article presents the analysis of 61 postcards about Porto Alegre, RS, in purpose to reveal the imaginary of the city updated by/in them as an authorized discourse. According to the imaginary of/in the postcards, Porto Alegre is a greatly enlarged city by its tangled buildings’ images while, at the same time, is empty, static, deprived of social relations. In the postcard’s city, the experimentation seems to be denied. The city is diurnal, doesn’t have movement, presented in cold colors and thought is contiguous with the lake, has little dialogue with it. Architecturally (architectural elements are the main focus of the images), the Porto Alegre of the postcards is just the downtown city where the largest concentration of buildings are located and recognized as a patrimony. In the postcards, which are also registration and memory, the imaginary and the local culture (gauchesca) incorporated are not very significant.Se presenta el análisis de 61 postales de Porto Alegre, RS con el objetivo de revelar el imaginario de la ciudad por ellos actualizado como el habla autorizada. De acuerdo con el imaginario de/en los postales, Porto Alegre es una ciudad hecha gigante en imagenes de predios enmarañados y, al mismo tiempo, vacía, estática, carente de relaciones sociales. Nella la experimentación parece ser negada. La ciudad de los postales es diurna, no presenta movimiento, tiene colores fríos y se yuxtapone al rio, pero poco dialoga com el. Arquitectónicamente (elementos arquitectónicos son el foco principal de las imagenes), la Porto Alegre de los postales es aquella de la región central donde esta la mayor concentración de predios declarados patrimonio. En los postales – que también son registro, memoria – el imaginario y la cultura gauchesca accionados son poco significativos.Apresenta-se a análise de 61 cartões-postais sobre Porto Alegre/RS com o objetivo de revelar o imaginário da cidade por eles/neles atualizado como fala autorizada. Segundo o imaginário dos/nos postais, Porto Alegre é uma cidade agigantada em imagens de prédios emaranhados e, ao mesmo tempo, vazia, estática, tolhida de relações sociais. Nela a experimentação parece ser negada. A cidade dos postais é diurna, não tem movimento, tem cores frias e está justaposta ao rio, mas pouco dialoga com ele. Arquitetonicamente (elementos arquitetônicos são o principal foco das imagens), a Porto Alegre dos postais é a da região central onde se encontra a maior concentração de prédios reconhecidos como patrimônio. Nos postais – que também são registro, memória – o imaginário e a cultura gauchesca acionados são pouco expressivos.

Access to care issues adversely affect breast cancer patients in Mexico: oncologists’ perspective

Background: Despite recently implemented access to care programs, Mexican breast cancer (BC) mortality rates remain substantially above those in the US. We conducted a survey among Mexican Oncologists to determine whether practice patterns may be responsible for these differences. Methods: A web-based survey was sent to 851 oncologists across Mexico using the Vanderbilt University REDCap database. Analyses of outcomes are reported using exact and binomial confidence bounds and tests. Results: 138 participants (18.6% of those surveyed) from the National capital and 26 Mexican states, responded. Respondents reported that 58% of newly diagnosed BC patients present with stage III-IV disease; 63% undergo mastectomy, 52% axillary lymph node dissection (ALND) and 48% sentinel lymph node biopsy (SLNB). Chemotherapy is recommended for tumors > 1 cm (89%), positive nodes (86.5%), triple-negative (TN) (80%) and HER2 positive tumors (58%). Trastuzumab is prescribed in 54.3% and 77.5% for HER2 1 cm tumors, respectively. Tamoxifen is indicated for premenopausal hormone receptor (HR) positive tumors in 86.5% of cases and aromatase inhibitors (AI’s) for postmenopausal in 86%. 24% of physicians reported treatment limitations, due to delayed or incomplete pathology reports and delayed or limited access to medications. Conclusions: Even though access to care programs have been recently applied nationwide, women commonly present with advanced BC, leading to increased rates of mastectomy and ALND. Mexican physicians are dissatisfied with access to appropriate medical care. Our survey detects specific barriers that may impact BC outcomes in Mexico and warrant further investigation. Electronic supplementary material The online version of this article (doi:10.1186/1471-2407-14-658) contains supplementary material, which is available to authorized users