Resumo:
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.
