Electrical characterization of Si-based/SiO2/TiO2 heterostructures

Two heterostructures based in the junction of titanium oxide, TiO2, and flat or porous silicon, PS, substrates were fabricated and their electrical properties were investigated through measuring the current-voltage and impedance electrochemical spectroscopy curves. The structural characterization reveals the successful deposition of TiO2 into the porous structure, which was also confirmed by the functional group analysis by the Fourier transform infrared spectroscopy. Concerning the electrical features, significant differences were found in charge transport behavior so that higher current intensity was recorded in the device based on porous silicon, despite its higher a.c resistance measured by impedance analysis. The fitting procedure of the current-voltage curves assuming the system is composed of three diodes points out that the possible cause for this behavior could be attributed to the role of the surface states in lowering the barrier potential. Such results are promising, as they allow the identification of the best methodology for the preparation of TiO2/silicon-based heterostructures that can be used in the photovoltaic and sensor field.