LaAlO3SrTiO3

LaAlO3/SrTiO3, often abbreviated LAO/STO, refers to a heterointerface formed when a thin film of lanthanum aluminate (LaAlO3) is grown on a single-crystal strontium titanate (SrTiO3) substrate. A conducting two-dimensional electron gas (2DEG) emerges at the interface, with conductivity typically observed when the LAO film reaches about four unit cells in thickness. The conducting region is confined to the first few nanometers of the SrTiO3 near the interface.

The origin is commonly attributed to the polar discontinuity between the polar LaAlO3, which consists of alternating LaO+ and AlO2- planes, and the nonpolar SrTiO3. To avoid the diverging electrostatic potential, electrons are transferred to the SrTiO3 conduction band at the interface, creating the 2DEG. Oxygen vacancies or cation intermixing can also contribute charge carriers, complicating the interpretation.

Growth is typically achieved by pulsed laser deposition or molecular beam epitaxy on TiO2-terminated SrTiO3 substrates, under carefully controlled oxygen pressures. Post-growth annealing in oxygen is often used to reduce vacancy-related conductivity and to improve interface quality.

Physically, the LAO/STO interface hosts high mobility carriers that can be tuned by electrostatic back-gating. The system exhibits superconductivity at low temperatures in some samples (on the order of 100 millikelvin to a few hundred millikelvin) and shows signs of magnetism and strong spin-orbit coupling due to broken inversion symmetry.

Due to its emergent interfacial phenomena, LAO/STO is studied as a platform for oxide electronics, including gate-tunable 2DEGs, nano-scale conducting channels, and potential quantum devices.