Lithography-free patterning of SrTiO${}_3$-based two-dimensional electron gases using direct atomic layer processing

Abstract

We present a scalable and lithography-free strategy for the realization of a two-dimensional electron gas (2DEG) in TiO${}_2$-patterned SrTiO${}_3$ (100) via Al deposition using magnetron sputtering. A 15 nm thick TiO${}_2$ 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 AlO${}_x$ overlayer is formed, and the region lacking the TiO${}_2$ pattern leads to the creation of oxygen vacancies in SrTiO${}_3$. These oxygen vacancies act as electron donors, populating the Ti 3$d$ conduction bands and giving rise to a confined 2DEG at the interface. Magneto-transport measurements reveal a sheet carrier density on the order of $\approx 5-7\times 10^{13}$ cm${}^{-2}$, comparable to values typically achieved in pulsed laser deposition-grown SrTiO${}_3$-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.

19 pages, 4 figures

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