Work function engineering via LaAlO3/SrTiO3 polar interfaces

By in situ Kelvin probe measurement combined with pulsed laser deposition, we have observed a change in the work function of (Nb:)SrTiO3(100) as LaAlO3(100) polar film is deposited, which strongly depends on the termination of the SrTiO3(100) surface and on the presence of the insulating SrTiO3(100) buffer layer. A sharp work function drop with LaAlO3(100) film deposition on a TiO2-terminated SrTiO3(100) surface would indicate the contribution of high-density electron gas at the interface to the unusual work function lowering. The present finding demonstrates that insulator-on-insulator structures using polar films could be a powerful platform to design artificial electronic states.