Oxygen vacancy formation energies in ${\mathrm{PbTiO}}_3/{\mathrm{SrTiO}}_3$ superlattice

Journal Article · Mon Jun 25 00:00:00 EDT 2018 · Physical Review Materials

DOI:https://doi.org/10.1103/PhysRevMaterials.2.064409· OSTI ID:1460196

Zhang, Lipeng ^[1]; Bredeson, Isaac ^[1]; Birenbaum, Axiel Y. ^[2]; Kent, P. R. C. ^[3]; Cooper, Valentino R. ^[2]; Ganesh, P. ^[4]; Xu, Haixuan ^[5]

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1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science. Computational Science and Engineering Division
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science
5. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering. Joint Inst. for Advanced Materials

The defect stability in a prototypical perovskite oxide superlattice consisting of $${\mathrm{SrTiO}}_{3}$$ and $${\mathrm{PbTiO}}_{3}$$ (STO/PTO) is determined by using first principles density functional theory calculations. Specifically, the oxygen vacancy formation energies $${E}_{\mathrm{v}}$$ in the paraelectric and ferroelectric phases of a superlattice with four atomic layers of STO and four layers of PTO (4STO/4PTO) are determined and compared. The effects of charge state, octahedral rotation, polarization, and interfaces on $${E}_{\mathrm{v}}$$ are examined in this paper. The formation energies vary layer by layer in the superlattices, with $${E}_{\mathrm{v}}$$ being higher in the ferroelectric phase than that in the paraelectric phase. The two interfaces constructed in these oxide superlattices, which are symmetrically equivalent in the paraelectric systems, exhibit very different formation energies in the ferroelectric superlattices and this can be seen to be driven by the coupling of ferroelectric and rotational modes. At equivalent lattice sites, $${E}_{\mathrm{v}}$$ of charged vacancies is generally lower than that of neutral vacancies. Octahedral rotations $$({\mathrm{a}}^{0}{\mathrm{a}}^{0}{\mathrm{c}}^{{-}})$$ in the superlattices have a significant effect on $${E}_{\mathrm{v}}$$, increasing the formation energy of vacancies located near the interface but decreasing the formation energy of the oxygen vacancies located in the bulk-like regions of the STO and PTO constituent parts. The formation-energy variations among different layers are found to be primarily caused by the difference in the local relaxation at each layer. Finally, these fundamental insights into the defect stability in perovskite superlattices can be used to tune defect properties by controlling the constituent materials of superlattices and interface engineering.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); ORNL Laboratory Directed Research and Development (LDRD) Program; The Univ. of Tennessee (UT) Science Alliance Joint Directed Research and Development Program (United States)
• Grant/Contract Number: AC05-00OR22725; AC02-05CH11231
• OSTI ID: 1460196
• Alternate ID(s): OSTI ID: 1457079
• Journal Information: Physical Review Materials, Vol. 2, Issue 6; ISSN 2475-9953
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
crystal defects
ferroelectrics
superlattices