Estudo das propriedades de transporte elétrico em heteroestruturas baseadas em ZnO/CdO

Abstract

This work presents a study on the electrical transport properties of ZnO/CdO semiconductor heterostructures grown by the Spray Pyrolysis (SP) technique, as well as a morphological characterization of the samples. Magnetotransport measurements performed with the ZnO/CdO sample grown on silicon (Si) showed Shubnikov de-Haas (SdH) quantum oscillations associated with the depletion region formed at the interface between zinc and cadmium oxides, which may be related to a confinement of a two-dimensional electron gas. Such non phenomenon was observed in the sample grown in glass. From the analysis of oscillations, it was possible to compare magnetoresistance (MR) measurements between those grown on silicon and glass, leading to the understanding that the formation of two-dimensional gas is related to the crystallinity of the silicon substrate. The structural and morphological properties were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), allowing to verify differences between oxide deposits on the surfaces of glass substrates and silicon, indicating that the oxide deposited on silicon substrate has better crystallinity. Hall Effect characterization results between temperatures of 300 K and 77 K for three CdO samples grown on Si substrate by the SP technique are also presented. Of these samples, two underwent a heat treatment process in an atmosphere at 500ºC, one submitted to an atmosphere of O2 and the other one in N2. The morphological characterization of these samples was also performed by the techniques of XRD, SEM and EDS. It was verified by the XRD technique that for samples submitted to heat treatment, there was an increase in crystallite size, and this leads to a change in the surface of the films, confirmed by SEM and EDS. These morphological changes lead to a variation in electrical properties confirmed by the Hall Effect and photoconductivity.