Direct Observation of Large Atomic Polar Displacements in Epitaxial Barium Titanate Thin Films

被引:12
作者
Wu, HsinWei [1 ]
Lu, Sirong [1 ]
Aoki, Toshihiro [2 ]
Ponath, Patrick [3 ]
Wang, Jian [4 ]
Young, Chadwin [4 ]
Ekerdt, John G. [5 ]
McCartney, Martha R. [6 ]
Smith, David J. [6 ]
机构
[1] Arizona State Univ, Sch Engn Matter Transport & Energy, Tempe, AZ 85287 USA
[2] Arizona State Univ, LeRoy Eyring Ctr Solid State Sci, Tempe, AZ 85287 USA
[3] Univ Texas Austin, Dept Phys, Austin, TX 78712 USA
[4] Univ Texas Dallas, Dept Mat Sci & Engn, Dallas, TX 75080 USA
[5] Univ Texas Austin, Dept Chem Engn, Austin, TX 78712 USA
[6] Arizona State Univ, Dept Phys, Tempe, AZ 85287 USA
关键词
aberration-corrected scanning transmission electron microscopy; electron energyloss spectroscopy; flexoelectricity; large atomic polar displacements; oxygen vacancies; polarization; SELF-POLARIZATION; BATIO3; FILMS; FERROELECTRICITY; BIFEO3; ENHANCEMENT; TEMPERATURE; ALGORITHM; CONTRAST;
D O I
10.1002/admi.202000555
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The development of ferroelectric perovskite oxides having a controlled polarization direction is an ongoing and challenging topic of research. Here direct observation of large atomic polar displacements, which correspond to a polar density of approximate to 0.9 C m(-2)pointing upward, in an epitaxial BaTiO(3)film grown by molecular beam epitaxy on a SrTiO(3)substrate is reported. Aberration-corrected scanning transmission electron microscopy is used to map the polarization displacement with unit-cell resolution. Oxygen vacancies and other types of defects are examined and mapped using electron energy-loss near-edge structure analysis. The contributions from strain, strain gradient, and defects are quantitatively modeled in order to explain the large polarization. Calculations show that strain (through a defect dipole-enhanced polarization) creates the large atomic polar displacements, and strain gradient (through inverse Vegard electrochemical strain effect) compensates the polarization. These two effects may explain the preferred polarization direction and the anomalous flexoelectric effect in ferroelectric thin films.
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页数:8
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