Probing electronic defect states in manganite/SrTiO3 heterostructures by surface photovoltage spectroscopy

Abstract: The energetic distribution of electronic defect states in oxide heterostructures made of ultrathin lanthanum manganite (La0.7Ca0.3MnO3, La0.7Ce0.3MnO3) films on SrTiO3 substrates is investigated by surface photovoltage (SPV) spectroscopy. Within a comparative evaluation of the SPV spectra of both the film/substrate structures and pure substrates at different temperatures we were able to elaborate a map of defect states across the SrTiO3-bandgap and we find that the defect state distribution is mainly affected by the substrate, i.e., no specific film-induced defect states were detected. Possible origins of the defect states are discussed within the framework of a semiconductor band scheme, taking into account complementary photoconductivity and SPV transient data. [Copyright &y& Elsevier]