Charge transfer and re-distribution in the TiO2-SrTiO3hetero-structure

This work examined the charge density distribution in the TiO 2 -SrTiO 3 hetero-structure using thermoelectric data reported in the literature. The first part of our work was to identify the equation necessary to extract charge densities. Our findings suggested that the observed thermoelectric power was best described by an equation applicable to a metal. Together with a distributed model that accounted for the layered structure, we computed the charge densities in the different layers. As observed, the charge density in the SrTiO 3 substrate was high (> 10 24 m −3 ) nonetheless in agreement with the value extracted from the depth profile measurement. Proportionally, the interface charge density was also very high (~ 10 28 m −3 ). Using these values, we computed the "effective" charge spread from the sheet conductance data, which was of the order of hundreds of microns. We had found no evidence that such charge spread could have originated from the interface and tended to believe that they were linked to oxygen vacancies embedded in the substrate. This was confirmed by a reduced charge spread when the top TiO 2 layer had been removed. In general, we showed that the thermoelectric power and the power factor were dominated by the properties of the substrate.