Control of electronic conduction at an oxide heterointerface using surface polar adsorbates

The interface between LaAlO3 and SrTiO3 possesses a range of intriguing properties, notably a proposed connection between the surface state of the LaAlO3 and the conductivity buried in the SrTiO3. Here we study the effect of the surface adsorption of a variety of common laboratory solvents on the conductivity at the interface between LaAlO3 and SrTiO3. We show that the application of chemicals such as acetone, ethanol, and water can induce a large change in the conductivity, and, in particular, an insulator to metal transition around the critical LaAlO3 thickness. This phenomenon is observed only for polar solvents. These data provide experimental evidence for a general polarization-facilitated electronic transfer mechanism.