Nunes, P., Braz Fernandes Silva Fortunato Martins F. M. R. J. "
Structural characterisation of zinc oxide thin films produced by spray pyrolysis."
Key Engineering Materials. 230-232 (2002): 599-602.
AbstractIn this work, we present a study of the effect of temperature, type and concentration of the dopant on the structural characteristics of ZnO thin films produced by spray pyrolysis; the crystallite size has been determined from profile peak shape analysis. These results are compared to the electrical characterisation performed on these materials. The effect of the dopant on the properties of ZnO thin films depends on its characteristics, mainly its ionic radius. Al, Ga and In have been studied as dopants, the best one being In, since it leads to the lowest resistivity.
Lopes, A., P. Nunes, P. Vilarinho, R. Monteiro, E. Fortunato, and R. Martins. "
Study of the sensing mechanism of SnO2 thin-film gas sensors using hall effect measurements."
Key Engineering Materials. 230-232 (2002): 357-360.
AbstractHall effect measurements are one of the most powerful techniques for obtaining information about the conduction mechanism in polycrystalline semiconductor materials, which is the basis for understanding semiconductor gas sensors. In order to investigate the correlation between the microscopic characteristics and the macroscopic performances exhibited by undoped tin oxide gas sensors deposited by spray pyrolysis, Hall effect measurements were performed at different temperatures, from room temperature up to 500 K, and in the presence of two different atmospheres, air and methane. From these measurements, it was possible to infer the potential barrier and its dependence with the used atmosphere. The obtained results were analysed in terms of the oxygen mechanism at grain boundaries on the basis of the grain boundary-trapping model. In the presence of methane gas, the electrical resistivity decreases due to the lowering of the inter-grain boundary barrier height.