基于LaNiO3薄膜的复杂氧化物分子束外延生长和原位扫描隧道显微镜/谱研究

Researches on transition metal oxides have emerged as one of the focal and challenging issues in condensed matter physics. However slight variations of atomic crystal structure may dramatically influence the strong spin-orbital coupling interaction with the charge, spin, lattice, and orbital degrees of freedom, inducing new quantum states and novel properties. Therefore it is quite urgent to control the quality and purity of materials, as well as to make accurate resolution of their electronic structure in real space at the atomic scale. In this project, we propose to grow the transition metal oxide (LaNiO3 and LaSrMnO3) films by oxide molecular beam epitaxy (OMBE) technique, allowing us to obtain atomically flat films with well-distributed stoichiometry and precise film thickness well-controlled. By transferring the samples in ultra high vacuum condition, we will in situ study their real-space morphologies and electronic structure using superlow temperature and high magnetic field (0.4 K, 11 T) scanning tunneling microscope/spectroscopy (STM/STS). Since the growth and measurements are both carried out in high vacuum, we protect the sample at our utmost and expect to obtain the intrinsic properties of related materials. From the distributions of defects, the sites of special atoms and the polarity ((LaO)+ and (NiO2)- terminations, respectively) on the surfaces, we will investigate the close relationship between the local electronic structure and crystal configurations at the nano-scale, as well as the key roles of bonds between atoms, element composition, films thickness etc. By studying the strain effects, substitutions of other metals and surface doping, we will investigate how the lattice distortions and charge carriers affect the atomic coupling to electronic properties, providing insights into the underlying nature of strong correlated electrons. Our research will inspire new clues for exploring artificial heterostructures and interfaces.

过渡金属氧化物中复杂的结构和电子关联效应，是当前凝聚态物理学研究的热点和难点。但氧化物材料晶格结构在原子尺度的微小变化，常常引发强自旋轨道耦合与电荷、自旋、晶格以及轨道自由度之间相互作用的剧烈变化，诱导新奇的电子学性质。因此，如何对样品的质量和纯度进行准确控制，并在微观尺度上进行局域电子态的空间分辨显得尤为迫切。在本项目中，申请人将利用氧化物分子束外延生长技术，获得原子级平整、化学组分和层数精确可控的复杂氧化物（LaNiO3和LaSrMnO3）薄膜。通过真空接驳技术，实现对样品进行原位低温强磁场扫描隧道镜/谱（0.4 K，11 T）研究，尽可能测量样品本征性质。通过表征表面的缺陷、原子占据位和极性（(LaO)+和 (NiO2)-）等信息，从原子级别程度来获取特定原子、元素组分、薄膜层厚等微观晶格结构与电子态之间的关联作用，揭示晶格和电荷载流子的影响，为下一步人工调制异质结界面开拓新的思路。