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首页> 外文期刊>Physical review >Polar catastrophe and the structure of KTa_(1-x)Nb_xO_3 surfaces: Results from elastic and inelastic helium atom scattering
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Polar catastrophe and the structure of KTa_(1-x)Nb_xO_3 surfaces: Results from elastic and inelastic helium atom scattering

机译:极性灾难和KTa_(1-x)Nb_xO_3表面的结构:氦原子弹性和非弹性散射的结果

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摘要

The structure and dynamics of cleaved (001) surfaces of potassium tantalates doped with niobium, KTa_(1-x)Nb_xO_3 (KTN), with × ranging from 0% to 30%, were measured by helium atom scattering (HAS). Through HAS time-of-flight (TOF) experiments, a dispersionless branch (Einstein phonon branch) with energy of 13-14 meV was observed across the surface Brillouin zone in all samples. When this observation is combined with the results from earlier experimental and theoretical studies on these materials, a consistent picture of the stable surface structure emerges: After cleaving the single-crystal sample, the surface should be composed of equal areas of KO and TaO_2/NbO_2 terraces. The data, however, suggest that K~+ and O_2~ ions migrate from the bulk to the surface, forming a charged KO lattice that is neutralized primarily by additional K~+ ions bridging pairs of surface oxygens. This structural and dynamic modification at the (001) surface of KTN appears due to its formally charged KO(-1) and TaO_2/NbO_2(+1) layers and avoids a "polar catastrophe." This behavior is contrasted with the (001) surface behavior of the fluoride perovskite KMnF_3 with its electrically neutral KF and MnF_2 layers.
机译:通过氦原子散射(HAS)测量了掺杂铌的钽钽酸钾KTa_(1-x)Nb_xO_3(KTN)的劈裂(001)表面的结构和动力学,其变化范围为0%到30%。通过HAS飞行时间(TOF)实验,在所有样品的整个布里渊区中观察到能量为13-14 meV的无分散分支(爱因斯坦声子分支)。当将该观察结果与这些材料的早期实验和理论研究的结果相结合时,就会得到稳定表面结构的一致图片:裂解单晶样品后,表面应由等面积的KO和TaO_2 / NbO_2组成梯田。然而,这些数据表明,K〜+和O_2〜离子从主体迁移到表面,形成带电的KO晶格,该晶格主要由桥接表面氧对的额外K〜+离子中和。由于其正式带电的KO(-1)和TaO_2 / NbO_2(+1)层而出现在KTN(001)表面的这种结构和动态修饰,避免了“极性灾难”。此行为与具有电中性KF和MnF_2层的氟化钙钛矿KMnF_3的(001)表面行为形成对比。

著录项

  • 来源
    《Physical review》 |2015年第3期|035414.1-035414.5|共5页
  • 作者单位

    Department of Physics, Valdosta State University, Valdosta, Georgia 31698-0055, USA;

    Department of Physics, Florida State University, Tallahassee, Florida 32306-4350, USA;

    Department of Physics, Florida State University, Tallahassee, Florida 32306-4350, USA;

    Department of Physics, Florida State University, Tallahassee, Florida 32306-4350, USA,Florida State University-Panama City Campus, Panama City, FL 32405, USA Gulf Coast State College, Panama City, FL 32401, USA;

    Department of Physics, Florida State University, Tallahassee, Florida 32306-4350, USA;

    Department of Physics, Florida State University, Tallahassee, Florida 32306-4350, USA;

    Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA;

    Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    surface and interface dynamics and vibrations; oxide surfaces; atom scattering from surfaces (diffraction and energy transfer);

    机译:表面和界面的动力学和振动;氧化物表面原子从表面散射(衍射和能量转移);

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