Anisotropic two-dimensional electron gas at SrTiO3(110)

Z. Wang, Z. Zhong, X. Hao, S. Gerhold, B. Stöger, M. Schmid, J. Sánchez-Barriga, A. Varykhalov, C. Franchini, K. Held, U. Diebold

Institut für Angewandte Physik, Technische Universität Wien, 1040 Wien, Austria

Proc. Natl. Acad. Sci. USA 111 (2014) 3933-3937

Two-dimensional electron gases (2DEGs) at oxide heterostructures are attracting considerable attention, as these might one day substitute conventional semiconductors at least for some functionalities. Here we present a minimal setup for such a 2DEG—the SrTiO3(110)-(4 × 1) surface, natively terminated with one monolayer of tetrahedrally coordinated titania. Oxygen vacancies induced by synchrotron radiation migrate underneath this overlayer; this leads to a confining potential and electron doping such that a 2DEG develops. Our angle-resolved photoemission spectroscopy and theoretical results show that confinement along (110) is strikingly different from the (001) crystal orientation. In particular, the quantized subbands show a surprising "semiheavy" band, in contrast with the analog in the bulk, and a high electronic anisotropy. This anisotropy and even the effective mass of the (110) 2DEG is tunable by doping, offering a high flexibility to engineer the properties of this system.

Corresponding author: Ulrike Diebold (diebold at iap_tuwien_ac_at).

You can download a PDF file of this open-access article from the Proceedings of the National Academy of Sciences of the United States of America (PNAS).

A preprint is available at