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Composite semiconductor nanostructures will contribute in large measure for the future generation of cost effective optoelectronic devices. In order to advance the progress it is important to understand the mechanism of charge injection, transport and recombination in these systems. Impedance spectroscopy (IS) is a relatively old and powerful method for characterizing many of the electrical properties of materials and their interfaces. In this study, the impedance of composite porous films of SnO 2 /ZnO and SnO 2 /TiO 2 have been taken into consideration and their behaviour in composite films was analyzed using IS to describe the mechanism of charge carrier transportation. The composites of SnO 2 and ZnO showed higher resistivity than their pure form and when SnO 2 : ZnO is in 1:1 ratio the resistivity of the composite film was the lowest (7.6 × 10 4 kΩ m). When the percentage of SnO 2 is around 40 % and 90 % the resistivity of the films were higher where each of these cases could be explained by the depletion of electrons in the conduction band of SnO 2 and ZnO at the interface. In contrast to the SnO 2 and ZnO composite films, the minimum resistivity of 5.86 × 10 5 Ωm was obtained for SnO 2 and TiO 2 composite films when SnO 2 is 33 %, which is lower than when they are in pure form. This low resistivity of both composite films is possibly attributed to the formation of a super structure in the composites where the electrons transport ballistically in mini bands.

Impedance spectroscopy (IS) subsumes the small signal measurement of the linear electrical response of a material of interest including electrode effects and the subsequent analysis of the response to yield useful information about physicochemical properties of the systems. In the majority of cases, the nanostructured films are better represented by a more complicated network of resistances and capacitances, so-called equivalent circuit. IS analysis generally makes a considerable use of these equivalent circuits.Films made from SnO2 and MgO have been taken into consideration and analyzed using IS to find the dielectric properties. Analyzing the Nyquist plots, the sheet resistance of the CTO glass was found to be around 610 Ω. But the parallel resistance of the film varied dramatically while altering the composition.10% of MgO in the SnO2/MgO composite showed a high impedance which is in two orders of magnitude higher than pure MgO. This is due to the confinement of electrons in quantum well structure formed by layer of MgO around SnO2 particles. The dielectric loss is also found to be minimal at this composition. The variation of real and imaginary parts of permittivity of the composite films of SnO2 and MgO are being discussed for different compositions in this study. SnO2 and MgO composite films of 10% MgO could find applications in devices such as capacitors and thin film transistors to be used as a novel dielectric.

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