"Built-in and induced polarization across LaAlO3/SrTiO3 heterojunctions"

Guneeta Singh-Bhalla: Christopher Bell, Jayakanth Ravichandran, Wolter Siemons, Yasuyuki Hikita, Sayeef Salahuddin, Arthur F. Hebard, Harold Y. Hwang, and Ramamoorthy Ramesh; Nature Physics, 01/17/11.

Additional Authors: Christopher Bell, Jayakanth Ravichandran, Wolter Siemons, Yasuyuki Hikita, Sayeef Salahuddin, Arthur F. Hebard, Harold Y. Hwang, and Ramamoorthy Ramesh

Abstract:

Ionic crystals terminated at oppositely charged polar surfaces are inherently unstable and expected to undergo surface reconstructions to maintain electrostatic stability. Essentially, an electric field that arises between oppositely charged atomic planes gives rise to a built-in potential that diverges with thickness. Here we present evidence of such a built-in potential across polar LaAlO3 thin films grown on SrTiO3 substrates, a system well known for the electron gas that forms at the interface. By carrying out tunnelling measurements between the electron gas and metallic electrodes on LaAlO3 we measure a built-in electric field across LaAlO3 of 80.1 meV Å−1. In addition, capacitance measurements reveal the presence of an induced dipole moment across the heterostructure. We foresee use of the ionic built-in potential as an additional tuning parameter in both existing and future device architectures, especially as atomic control of oxide interfaces gains widespread momentum.