Cui Yi, Shao Xiang, Prada Stefano, Giordano Livia, Pacchioni Gianfranco, Freund Hans-Joachim, Nilius Niklas
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.
Phys Chem Chem Phys. 2014 Jul 7;16(25):12764-72. doi: 10.1039/c4cp01565g.
The functionality of doped oxides sensitively depends on the spatial distribution of the impurity ions and their interplay with compensating defects in the lattice. In our combined scanning tunneling microscopy (STM) and density functional theory (DFT) study, we analyze defects occurring in Mo-doped CaO(001) films at the atomic scale. By means of topographic imaging, we identify common point and line defect in the doped oxide, in particular Mo donors and compensating Ca vacancies. The influence of charged defects on the oxide electronic structure is analyzed by STM conductance spectroscopy. The experimentally observed defect features are connected to typical point defects in the CaO lattice by means of DFT calculations. Apart from the identification of individual defects, our study reveals a pronounced inhomogeneity of the oxide electronic structure, reflecting the uneven spatial distribution of dopants in the lattice. Our results provide the basis for a better understanding of adsorption and reaction patterns on doped oxides, as widely used in heterogeneous catalysis.
掺杂氧化物的功能敏感地依赖于杂质离子的空间分布及其与晶格中补偿缺陷的相互作用。在我们结合扫描隧道显微镜（STM）和密度泛函理论（DFT）的研究中，我们在原子尺度上分析了Mo掺杂的CaO(001)薄膜中出现的缺陷。通过形貌成像，我们识别出掺杂氧化物中常见的点缺陷和线缺陷，特别是Mo施主和补偿性Ca空位。通过STM电导光谱分析了带电缺陷对氧化物电子结构的影响。通过DFT计算，将实验观察到的缺陷特征与CaO晶格中的典型点缺陷联系起来。除了识别单个缺陷外，我们的研究还揭示了氧化物电子结构的明显不均匀性，这反映了晶格中掺杂剂的不均匀空间分布。我们的结果为更好地理解掺杂氧化物上的吸附和反应模式提供了基础，掺杂氧化物在多相催化中被广泛使用。
