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Nunca mais voltas ao Cais? Percepções sociais e políticas sobre os Cais da Ria ...
Robaina, M.; Martins, F.; Figueiredo, E.; Albuquerque, H.As comunidades existentes em torno da Ria de Aveiro sempre mantiveram com esta uma forte afinidade. Este ecossistema foi sempre utilizado como fonte de recursos, sendo que as populações mais ribeirinhas viviam em função do que a “Ria” lhes concedia – o sal, o moliço, a pesca, o transporte lagunar e mesmo a agricultura. Por esta razão, foram construídos vários cais de acostagem que serviam de suporte às diversas...
Low frequency oscillations and bifurcation diagram in semi-insulating GaAs samples
Silva,R. L. da; Albuquerque,H. A.; Rubinger,R. M.; Oliveira,A. G. de; Ribeiro,G. M.; Rodrigues,W. N.We present an experimental study of bifurcation diagrams from low frequency current oscillations (LFO) measurements obtained from semi-insulating GaAs samples grown by low temperature molecular beam Epitaxy (LT-MBE). The considered growth temperatures were 215ºC and 265ºC. LFO are considered to be spontaneously generated oscillations under constant applied bias V. These oscillations were measurement and recorde...
Variable range hopping conduction in low-temperature molecular beam epitaxy GaAs
Rubinger,R. M.; Albuquerque,H. A.; Silva,R. L. da; Oliveira,A. G. de; Ribeiro,G. M.; Rodrigues,W. N.; Rubinger,C. P. L; Moreira,M. V. B.Electric transport properties measured by Van der Pauw resistivity experiments of Low-Temperature Molecular Beam Epitaxy (LT-MBE) GaAs samples are used to identify a method to improve the resistivity of GaAs material. We present results on five samples grown at 265, 310, 315, 325, and 345 ºC. The electric measurements were carried out at temperatures ranging from 130 to 300 K. In this temperature range the domi...
Modeling chaotic current oscillations in semi-insulating GaAs with rate-equatio...
Albuquerque,H. A.; Silva,R. L. da; Rubinger,R. M.; Oliveira,A. G. de; Ribeiro,G. M.; Rodrigues,W. N.We investigated the effect of adding the field-dependent recombination process, namely field-enhanced trapping, to the generation-recombination processes of charge carriers that model current oscillations in semiconductors. The main new features arising from this modification are identified in bifurcation diagrams with the electric field as the control parameter. The characteristic of the bifurcation diagrams i...
Hall effect in InAs/GaAs superlattices with quantum dots: identifying the prese...
Rubinger,R.M.; Ribeiro,G.M.; Oliveira,A.G. de; Albuquerque,H.A.; Silva,R.L. da; Rodrigues,W.N.; Moreira,M.V.B.We have carried out van der Pauw resistivity and Hall effect measurements on a series of Molecular Beam Epitaxy InAs/GaAs superlattice samples containing InAs quantum dots. Three growth parameters were varied, the InAs coverage, the number of repetitions of the InAs/GaAs layers, and the GaAs spacer thickness. The results can be grouped in two sets, those samples presenting low and high resistivity. The group pr...
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