Conductivity of LaAlO3/SrTiO3 Interfaces Made by Sputter Deposition

There is much interest in interfaces between insulating oxides, such as SrTiO3 (STO) and LaAlO3 (LAO), where a two dimensional electron gas can form due to the so-called polar discontinuity. These interfaces are mostly fabricated by Pulsed Laser Deposition (PLD). We have investigated such interfaces by reactive RF sputtering in a high-pressure oxygen atmosphere. The films are smooth and crystalline. Transmission Electron Microscopy indicates that the interfaces are sharp and continuous while Electron Energy Loss Spectroscopy data indicate some slight intermixing. However, we find these interfaces to be non-conducting. It appears that the sputtered interface is not electronically reconstructed in the way reported for films grown by PLD, notwithstanding the good structural quality and composition of the films.