Issue 38, 2021

Nature of the surface space charge layer on undoped SrTiO3 (001)

Abstract

SrTiO3, an ABO3-type perovskite structure, has been a popular choice of substrate for many important heterostructures, e.g., ferroelectric thin films and superlattices. As numerous exotic physical phenomena are closely related to delicate electron/ion exchanges at the interfacial layer between the substrate and overlayer, precise characterization of surface/interfacial properties has become the center of many research studies. In most cases of SrTiO3 research, Nb-doping is applied on the SrTiO3 surface in order to characterize electrical properties with a negligible effect of contact potential between SrTiO3 and overlayer. On the other hand, the presence of doping can possibly interfere with a correct interpretation of the surface defect states, which become critical to apprehend the electrical properties of heterostructures. In this report, the undoped SrTiO3 (001) surface is investigated utilizing ambient-pressure XPS (AP-XPS) and low energy electron diffraction (LEED). We identified the complete chemical/structural/electronic states of O and Sr vacancies on the undoped SrTiO3 surface from ultra-high vacuum (UHV, <10−9 mbar) to O2 gas pressure of 0.1 mbar conditions. Under oxygen pressure conditions, chemically stable SrO1+x surface oxide with a c(6 × 2) superstructure is formed, generating electron depletion and band bending, i.e., the formation of a space charge layer underneath the surface. On the other hand, under UHV, the surface oxide comes from the O vacancy, which has different electronic properties from those of Sr vacancy-related oxides.

Graphical abstract: Nature of the surface space charge layer on undoped SrTiO3 (001)

Supplementary files

Article information

Article type
Paper
Submitted
23 Jūl. 2021
Accepted
02 Sept. 2021
First published
16 Sept. 2021
This article is Open Access
Creative Commons BY-NC license

J. Mater. Chem. C, 2021,9, 13094-13102

Nature of the surface space charge layer on undoped SrTiO3 (001)

H. Lim, C. Song, M. Seo, D. Kim, M. Jung, H. Kang, S. Kim, K. Lee, Y. Yu, G. Kim, K. Kim and B. S. Mun, J. Mater. Chem. C, 2021, 9, 13094 DOI: 10.1039/D1TC03436G

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