The Vacancy-Induced Electronic Structure of the SrTiO3−δ Surface

Seyoung Cook; Maxwell T. Dylla; Richard A. Rosenberg; Zachary R. Mansley; G. Jeffrey Snyder; Laurence Marks; Dillon D. Fong

doi:10.1002/aelm.201800460

The Vacancy-Induced Electronic Structure of the SrTiO_3−δ Surface

Seyoung Cook, Maxwell T. Dylla, Richard A. Rosenberg, Zachary R. Mansley, G. Jeffrey Snyder, Laurence Marks, Dillon D. Fong^*

^*Corresponding author for this work

Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

16 Scopus citations

Abstract

The emergence of a 2D electron gas (2DEG) on the (001) surface of oxygen-deficient strontium titanate (SrTiO_3−δ) is investigated. Using in situ soft X-ray spectroscopy and effective mass modeling, a series of quantitative band diagrams are developed to describe the evolution of near-surface and bulk carrier concentrations, downward band bending, and Fermi level along a lateral gradient of oxygen vacancies formed on SrTiO_3−δ by direct-current resistive heating under ultrahigh vacuum conditions. Electrons are accumulated over a 3 nm region near the surface, confined within a potential well with saturated 300 meV downward band bending. The relation between Fermi levels and carrier concentrations near the surface suggests the density of states near the surface is much lower than the bulk density of states, which is consistent with the quantum-confined subbands of a 2DEG. The quantitative relationship between the surface and bulk electronic structures developed in this work provides a guide for precise engineering of the oxygen-vacancy-induced 2DEG in SrTiO₃.

Original language	English (US)
Article number	1800460
Journal	Advanced Electronic Materials
Volume	5
Issue number	1
DOIs	https://doi.org/10.1002/aelm.201800460
State	Published - Jan 2019

Funding

Work by S.C. and D.D.F. was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Materials Science Division. Use of the Advanced Photon Source was supported by the DOE, Office of Science, BES, under Contract No. DE-AC02-06CH11357. Work by M.T.D. and G.J.S. was supported by the National Science Foundation (NSF), Division of Materials Research (DMR) under Grant Nos. 1334713 and 1333335. Work by Z.R.M. was supported by the DOE (DE-FG02-03ER15457) through the Institute for Catalysis in Energy Processes at Northwestern University. Work by L.D.M. was supported by the DOE, Office of Science, BES, under Award No. DE-FG02-01ER45945.

Keywords

SrTiO surface
effective mass modeling
electronic structure
in-situ x-ray spectroscopy
oxygen vacancies

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials

Access to Document

10.1002/aelm.201800460

Cite this

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title = "The Vacancy-Induced Electronic Structure of the SrTiO3−δ Surface",

abstract = "The emergence of a 2D electron gas (2DEG) on the (001) surface of oxygen-deficient strontium titanate (SrTiO3−δ) is investigated. Using in situ soft X-ray spectroscopy and effective mass modeling, a series of quantitative band diagrams are developed to describe the evolution of near-surface and bulk carrier concentrations, downward band bending, and Fermi level along a lateral gradient of oxygen vacancies formed on SrTiO3−δ by direct-current resistive heating under ultrahigh vacuum conditions. Electrons are accumulated over a 3 nm region near the surface, confined within a potential well with saturated 300 meV downward band bending. The relation between Fermi levels and carrier concentrations near the surface suggests the density of states near the surface is much lower than the bulk density of states, which is consistent with the quantum-confined subbands of a 2DEG. The quantitative relationship between the surface and bulk electronic structures developed in this work provides a guide for precise engineering of the oxygen-vacancy-induced 2DEG in SrTiO3.",

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author = "Seyoung Cook and Dylla, {Maxwell T.} and Rosenberg, {Richard A.} and Mansley, {Zachary R.} and Snyder, {G. Jeffrey} and Laurence Marks and Fong, {Dillon D.}",

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AU - Snyder, G. Jeffrey

AU - Marks, Laurence

AU - Fong, Dillon D.

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N2 - The emergence of a 2D electron gas (2DEG) on the (001) surface of oxygen-deficient strontium titanate (SrTiO3−δ) is investigated. Using in situ soft X-ray spectroscopy and effective mass modeling, a series of quantitative band diagrams are developed to describe the evolution of near-surface and bulk carrier concentrations, downward band bending, and Fermi level along a lateral gradient of oxygen vacancies formed on SrTiO3−δ by direct-current resistive heating under ultrahigh vacuum conditions. Electrons are accumulated over a 3 nm region near the surface, confined within a potential well with saturated 300 meV downward band bending. The relation between Fermi levels and carrier concentrations near the surface suggests the density of states near the surface is much lower than the bulk density of states, which is consistent with the quantum-confined subbands of a 2DEG. The quantitative relationship between the surface and bulk electronic structures developed in this work provides a guide for precise engineering of the oxygen-vacancy-induced 2DEG in SrTiO3.

AB - The emergence of a 2D electron gas (2DEG) on the (001) surface of oxygen-deficient strontium titanate (SrTiO3−δ) is investigated. Using in situ soft X-ray spectroscopy and effective mass modeling, a series of quantitative band diagrams are developed to describe the evolution of near-surface and bulk carrier concentrations, downward band bending, and Fermi level along a lateral gradient of oxygen vacancies formed on SrTiO3−δ by direct-current resistive heating under ultrahigh vacuum conditions. Electrons are accumulated over a 3 nm region near the surface, confined within a potential well with saturated 300 meV downward band bending. The relation between Fermi levels and carrier concentrations near the surface suggests the density of states near the surface is much lower than the bulk density of states, which is consistent with the quantum-confined subbands of a 2DEG. The quantitative relationship between the surface and bulk electronic structures developed in this work provides a guide for precise engineering of the oxygen-vacancy-induced 2DEG in SrTiO3.

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