Lithography-free patterning of SrTiO3-based two-dimensional electron gases using direct atomic layer processing

We present a scalable and lithography-free strategy for the realization of a two-dimensional electron gas (2DEG) in TiO2-patterned SrTiO3 (100) via Al deposition using magnetron sputtering. A 15 nm thick TiO2 layer, deposited by direct atomic layer processing, is employed to spatially define the conducting regions, enabling direct transport measurements without post-growth microfabrication. Upon Al deposition, an insulating AlOx overlayer is formed, and the region lacking the TiO2 pattern leads to the creation of oxygen vacancies in SrTiO3. These oxygen vacancies act as electron donors, populating the Ti 3d conduction bands and giving rise to a confined 2DEG at the interface. Magneto-transport measurements reveal a sheet carrier density on the order of ≈5–7 × 1013 cm−2, comparable to values typically achieved in pulsed laser deposition-grown SrTiO3-based heterostructures, along with effective electrostatic tunability. This work demonstrates a simple, cost-effective, and industry-compatible route for engineering oxide 2DEGs, providing a versatile platform for scalable device fabrication and interfacial transport studies.