Unveiling the Electronic Structure of Grain Boundaries in Anatase with Electron Microscopy and First-Principles Modeling

TY - JOUR

T1 - Unveiling the Electronic Structure of Grain Boundaries in Anatase with Electron Microscopy and First-Principles Modeling

AU - Quirk, James A

AU - Miao, Bin

AU - Feng, Bin

AU - Kim, Gowoon

AU - Ohta, Hiromichi

AU - Ikuhara, Yuichi

AU - McKenna, Keith P

N1 - © 2021 The Authors

PY - 2021/11/10

Y1 - 2021/11/10

N2 - Polycrystalline anatase titanium dioxide has drawn great interest, because of its potential applications in high-efficiency photovoltaics and photocatalysts. There has been speculation on the electronic properties of grain boundaries but little direct evidence, because grain boundaries in anatase are challenging to probe experimentally and to model. We present a combined experimental and theoretical study of anatase grain boundaries that have been fabricated by epitaxial growth on a bicrystalline substrate, allowing accurate atomic-scale models to be determined. The electronic structure in the vicinity of stoichiometric grain boundaries is relatively benign to device performance but segregation of oxygen vacancies introduces barriers to electron transport, because of the development of a space charge region. An intrinsically oxygen-deficient boundary exhibits charge trapping consistent with electron energy loss spectroscopy measurements. We discuss strategies for the synthesis of polycrystalline anatase in order to minimize the formation of such deleterious grain boundaries.

AB - Polycrystalline anatase titanium dioxide has drawn great interest, because of its potential applications in high-efficiency photovoltaics and photocatalysts. There has been speculation on the electronic properties of grain boundaries but little direct evidence, because grain boundaries in anatase are challenging to probe experimentally and to model. We present a combined experimental and theoretical study of anatase grain boundaries that have been fabricated by epitaxial growth on a bicrystalline substrate, allowing accurate atomic-scale models to be determined. The electronic structure in the vicinity of stoichiometric grain boundaries is relatively benign to device performance but segregation of oxygen vacancies introduces barriers to electron transport, because of the development of a space charge region. An intrinsically oxygen-deficient boundary exhibits charge trapping consistent with electron energy loss spectroscopy measurements. We discuss strategies for the synthesis of polycrystalline anatase in order to minimize the formation of such deleterious grain boundaries.

U2 - 10.1021/acs.nanolett.1c03099

DO - 10.1021/acs.nanolett.1c03099

M3 - Article

C2 - 34724619

SN - 1530-6984

VL - 21

SP - 9217

EP - 9223

JO - Nano Letters

JF - Nano Letters

IS - 21

ER -