Effect of the GaAsP shell on optical properties of self-catalyzed GaAs nanowires grown on silicon

We realize growth of self-catalyzed core-shell GaAs/GaAsP nanowires (NWs) on Si substrates using molecular-beam epitaxy. Transmission electron microscopy (TEM) of single GaAs/GaAsP NWs confirms their high crystal quality and shows domination of the zinc-blende phase. This is further confirmed in optics of single NWs, studied using cw and time-resolved photoluminescence (PL). A detailed comparison with uncapped GaAs NWs emphasizes the effect of the GaAsP capping in suppressing the non-radiative surface states: significant PL enhancement in the core-shell structures exceeding 2000 times at 10K is observed; in uncapped NWs PL is quenched at 60K whereas single core-shell GaAs/GaAsP NWs exhibit bright emission even at room temperature. From analysis of the PL temperature dependence in both types of NW we are able to determine the main carrier escape mechanisms leading to the PL quench

BRS Timbó: nova cultivar de feijão do grupo roxo para Mato Grosso do Sul.

bitstream/item/24678/1/COT2005114.pdfDocumento on-line

BRS Vereda: nova cultivar de feijão do grupo Rosinha para Mato Grosso do Sul.

bitstream/item/24679/1/COT2005113.pdfDocumento on-line

Purification and Crystal Growth of the Bismuth (III) Iodide-influence of Trace Impurities on the Crystal Quality

This work describes the experimental procedure of purification and preparation of BiI3 crystals by Repeated Vertical Bridgman technique, aiming a future application of this semiconductor crystal as a room temperature radiation detector. The BiI3 powder used as raw material was purified three times and, at each purification, the crystal was evaluated by systematic measurements of the reduction of the impurities, crystalline structure, stoichiometry and surface morphology. The reduction of the trace metal impurities in the BiI3, at each purification, was analyzed by Instrumental Neutron Activation Analysis (INAA), in order to evaluate the efficiency of the purification technique established in this work. It was demonstrated that the Repeated Bridgman technique is effective to reduce the concentration of many impurities in BiI3, such as Ag, As, Br, Cr, K, Mo, Na and Sb. The crystalline structure of the BiI3 crystal purified twice and three times was similar to BiI3 pattern. However, for BiI3 powder and purified once, an intensity contribution of the BiOI was observed in the diffractograms. Improvement in the stoichiometric ratio was observed at each purification step, as well as the crystal surface morphology

Soja: escolha a variedade que melhor se adapta a sua região: Lambari, Mandi, Surubi.

Descrição da variedade, reações às principais doenças, área de recomendação, das cultivares MS/BR-57 (Lambari), MS/BR-59 (Mandi), MS/BR-61 (Surubi).bitstream/item/95861/1/Soja-escolha-a-variedade-que-melhor-se-adapta-a-sua-regiao.pdf1 folder