Minority anion substitution by Ni in ZnO

We report on the lattice location of implanted Ni in ZnO using the beta(-) emission channeling technique. In addition to the majority substituting for the cation (Zn), a significant fraction of the Ni atoms occupy anion (O) sites. Since Ni is chemically more similar to Zn than it is to O, the observed O substitution is rather puzzling. We discuss these findings with respect to the general understanding of lattice location of dopants in compound semiconductors. In particular, we discuss potential implications on the magnetic behavior of transition metal doped dilute magnetic semiconductors. (C) 2013 AIP Publishing LLC

Piezoelectric resonators based on self-assembled diphenylalanine microtubes

Piezoelectric actuation has been widely used in microelectromechanical devices including resonance-based biosensors, mass detectors, resonators, etc. These were mainly produced by micromachining of Si and deposited inorganic piezoelectrics based on metal oxides or perovskite-type materials which have to be further functionalized in order to be used in biological applications. In this work, we demonstrate piezoelectrically driven micromechanical resonators based on individual self-assembled diphenylalanine microtubes with strong intrinsic piezoelectric effect. Tubes of different diameters and lengths were grown from the solution and assembled on a rigid support. The conducting tip of the commercial atomic force microscope was then used to both excite vibrations and study resonance behavior. Efficient piezoelectric actuation at the fundamental resonance frequency approximate to 2.7 MHz was achieved with a quality factor of 114 for a microtube of 277 mu m long. A possibility of using piezoelectric dipeptides for biosensor applications is discussed. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4793417

Valor potencial de pesquisa de micobactinas para identificação de micobactérias na prática clínica

RESUMO: A produção de micobactinas foi feita utilizando o método em duas etapas do ácido ctilenadiamino-di-o-hidroxifenílacético (EDDHA). Novas propostos de sistemas de solventes foram utilizadas para analisar 17 espécies micobacterianans em cromatografia por camada fina. Todas as espécies do complexo MAIS (incluindo um exemplo de cada serotipo do complexo M. avuium) formaram micobactinas idênticas. De acordo com resultados prévios, cada uma das espécies dos groupos. M. kansasii, M. marinum, e M. terrae, M. gastri,·M.·triviale formaram microbactinas distintas. M. szulgai e M. flavescenes formaram um mesmo padrâo de micobactinas, diferente doqueles encontrados noutras espécies microbacterianas incluindo M. gordonae e M. asiaticum. Em contradição com observações precedentes sobre o complexo M. tuberculosis, as nossas investigações mostraram·diferenças nos padrões de micobactinas entre M. bovis BCG e M. tuberculosis. O método proposto para a produção de micobactinas é compatível com um esquema de identificação micobacteriana. SUMMARY: The ethylenediamine-di-o-hydroxyphenyl-acetic acid (EDDHA) two-step method was used for mycobactin production. New solvant systems were proposed for their analysis by TLC and were used to examine 17 mycobacterial species. All the species tested within the MAIS complex (including one example from each serotype of the M. avium complex) formed identical mycobactins. Result concerning M. kansasii and M. marinam, as well, as. M. terrae, M. gastri and M. triviale were in agreement with the previous findings, i.t each specias formed a distinet mycobactin. M. szulgai and M. flavescens, formed identical mycobactin patterns, differing from those or other mycobacterial species tested including M. gordonae and M. asiaticum. Contrary to previous observations concerning the M. tuberculosis complex, our investigations showed differences between the M.· bovis BCG and M. tuberculosis mycobactin profiles. The method proposed for mycobactin production and detection is directly applicable in classical identification schemes for mycobacteria. Palavaras-chave: Micobactinas, espécies Mycobacterium, Key-words: Mycobactins, Mycobacterium specie

A generalized fitting tool for analysis of two-dimensional channeling patterns

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Lattice location and thermal stability of implanted nickel in silicon studied by on-line emission channeling

We have studied the lattice location of implanted nickel in silicon, for different doping types (n, n, and p). By means of on-line emission channeling, 65Ni was identified on three different sites of the diamond lattice: ideal substitutional sites, displaced bond-center towards substitutional sites (near-BC), and displaced tetrahedral interstitial towards anti-bonding sites (near-T). We suggest that the large majority of the observed lattice sites are not related to the isolated form of Ni but rather to its trapping into vacancy-related defects produced during the implantation. While near-BC sites are prominent after annealing up to 300-500 °C, near-T sites are preferred after 500-600 °C anneals. Long-range diffusion starts at 600-700 °C. We show evidence of Ni diffusion towards the surface and its further trapping on near-T sites at the Rp/2 region, providing a clear picture of the microscopic mechanism of Ni gettering by vacancy-type defects. The high thermal stability of near-BC sites in n-type Si, and its importance for the understanding of P-diffusion gettering are also discussed. © 2014 AIP Publishing LLC.status: publishe

A generalized fitting tool for analysis of two-dimensional channeling patterns

The acquisition of two-dimensional (2D) channeling patterns is gaining increased popularity within the ion beam community. However, with the exception of emission channeling experiments for the lattice location of radioactive impurities, quantitative analysis of such patterns is rarely found. We present a general description of the statistical data analysis methodology for 2D channeling patterns, which consists of comparing experimental data by means of a fit procedure to theoretical yield distributions. The developed software allows for chi-square or maximum likelihood-based fits, optimizing the orientation of the theoretical vs the experimental pattern, as well as the best choice of random level, and providing fractions for the contributions from several theoretical patterns related to different lattice sites. Optionally also the angular resolution can be used as a fit parameter. Use of the software is illustrated by examples of electron emission channeling from $^{27}$Mg in GaN, as well as $^{4}$He RBS channeling from Ge

Lattice sites of implanted Na in GaN and AlN in comparison to other light alkalis and alkaline earths

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Lattice location study of low-fluence ion-implanted In-124 in 3C-SiC

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Lattice sites of ion-implanted Mn, Fe and Ni in 6H-SiC

© 2017 IOP Publishing Ltd. Using radioactive isotopes produced at the CERN-ISOLDE facility, the lattice location of the implanted transition metal (TM) ions 56Mn, 59Fe and 65Ni in n-type single-crystalline hexagonal 6H-SiC was studied by means of the emission channeling technique. TM probes on carbon coordinated tetrahedral interstitial sites (T C) and on substitutional silicon sites (S Si,h+k) were identified. We tested for but found no indication that the TM distribution on S Si sites deviates from the statistical mixture of 1/3 hexagonal and 2/3 cubic sites present in the 6H crystal. The TM atoms partially disappear from T C positions during annealing at temperatures between 500 °C and 700 °C which is accompanied by an increase on S Si and random sites. From the temperature associated with these site changes, interstitial migration energies of 1.7-2.7 eV for Mn and Ni, and 2.3-3.2 eV for Fe were estimated. TM lattice locations are compared to previous results obtained in 3C-SiC using the same technique.status: publishe