Department of Physics, Indiana University, Bloomington, Indiana, 47405, USA.
Department of Physics, Virginia Tech, Blacksburg, Virginia, 24061, USA.
Sci Rep. 2017 Aug 10;7(1):7740. doi: 10.1038/s41598-017-06785-w.
While pyrochlore iridate thin films are theoretically predicted to possess a variety of emergent topological properties, experimental verification of these predictions can be obstructed by the challenge in thin film growth. Here we report on the pulsed laser deposition and characterization of thin films of a representative pyrochlore compound BiIrO. The films were epitaxially grown on yttria-stabilized zirconia substrates and have lattice constants that are a few percent larger than that of the bulk single crystals. The film composition shows a strong dependence on the oxygen partial pressure. Density-functional-theory calculations indicate the existence of Bi antisite defects, qualitatively consistent with the high Bi: Ir ratio found in the films. Both Ir and Bi have oxidation states that are lower than their nominal values, suggesting the existence of oxygen deficiency. The iridate thin films show a variety of intriguing transport characteristics, including multiple charge carriers, logarithmic dependence of resistance on temperature, antilocalization corrections to conductance due to spin-orbit interactions, and linear positive magnetoresistance.
虽然烧绿石型碘化物薄膜在理论上被预测具有多种新兴拓扑性质，但由于薄膜生长的挑战，这些预测的实验验证可能会受到阻碍。在这里，我们报告了一种代表性的烧绿石化合物 BiIrO 的脉冲激光沉积和薄膜特性。这些薄膜在氧化钇稳定的氧化锆衬底上外延生长，晶格常数比体单晶大几个百分点。薄膜组成对氧分压有很强的依赖性。密度泛函理论计算表明存在 Bi 反位缺陷，这与薄膜中发现的高 Bi:Ir 比定性一致。Ir 和 Bi 的氧化态都低于其标称值，表明存在氧空位。碘化物薄膜表现出多种有趣的输运特性，包括多载流子、电阻随温度的对数依赖性、由于自旋轨道相互作用导致电导的反局域化修正以及线性正磁电阻。
