Conductivity of LaAlO/SrTiO3 Interfaces made by Sputter Deposition

We have investigated the properties of interfaces between LaAlO3 films grown on SrTiO3 substrates singly terminated by TiO2. We used RF sputtering in a high-pressure oxygen atmosphere. The films are smooth, with flat surfaces. Transmission Electron Microscopy shows atomically sharp and continuous interfaces while EELS measurements show some slight intermixing. The elemental ratio of La to Al measured by EDX is found to be 1.07. Importantly, we find these interfaces to be non-conducting, indicating that the sputtered interface is not electronically reconstructed in the way reported for films grown by Pulsed Laser Deposition because of the different interplay between stoichiometry, mixing and oxygen vacancies.