First principles study of transport properties of LaAlO3/SrTiO3 heterostructure with water adsorbates

Tuning transport properties of two-dimensional electron gas (2DEG) at the LaAlO3/SrTiO3 interface by surface modification is of great interest due to its rich physics and potential application in polar liquid or gas sensors. From first-principle calculations, we found that the adsorption of a thin layer of polar water molecules on the surface of LaAlO3 can remarkably enhance the carrier density of the interfacial 2DEG by over at least 50% which is qualitatively consistent with reported experimental result. This result sheds light on the charge coupling between surface polar molecules and interfacial 2DEG and suggests that sensor devices may be built using the hetero-oxide interfacial 2DEG.