Growth and characterization of off-stoichiometric LaVO3 thin films
Growth and characterization of off-stoichiometric LaVO3 thin films
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DOI：
10.1103/physrevmaterials.5.085006
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发表时间：
2021-08
影响因子：
3.4
通讯作者：
Biwen Zhang;Y. Xin;E. Karapetrova;J. Holleman;S. McGill;C. Beekman
中科院分区：
文献类型：
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作者：
Biwen Zhang;Y. Xin;E. Karapetrova;J. Holleman;S. McGill;C. Beekman
LaVO 3（LVO）被认为是一种很有前途的光致发光材料，因为它的强关联d电子可以促进每个入射光子产生多个电子-空穴对，这将导致器件效率的提高。在这项研究中，我们有意识地生长非化学计量LVO薄膜通过改变生长条件，如激光能量密度。我们的目的是研究偏离La：V化学计量比如何影响LVO薄膜的电子性质。我们发现，非化学计量比明显改变了薄膜的物理性质。结构表征表明，富La和富V薄膜都具有不同程度的结构变形，与仅从外延应变效应中预期的情况相比，富La（富V）薄膜显示出更大（更小）的面外晶格参数。这两种类型的膜在光学测量中显示出与本体LVO的行为的偏差，即，它们没有显示出预期的长程轨道顺序的特征，这可能是结构扭曲或结构域存在的结果。在传输测量中，富镧薄膜显示出清晰的电子相分离的签名伴随着温度引起的金属-绝缘体转变，而富钒薄膜表现为莫特绝缘体。面外晶格参数在确定输运性质中起着至关重要的作用，因为从Mott绝缘到无序诱导的相分离行为的交叉发生在晶格参数值为3.96 μ m附近，与先前报道的完全不同。
LaVO3 (LVO) has been proposed as a promising material for photovoltaics because its strongly correlated d electrons can facilitate the creation of multiple electron-hole pairs per incoming photon, which would lead to increased device efficiency. In this study, we intentionally grow off-stoichiometric LVO films by changing the growth conditions such as laser fluence. Our aim is to study how deviating La:V stoichiometries affect the electronic properties of LVO thin films. We find that the off-stoichiometry clearly alters the physical properties of the films. Structural characterization shows that both La-rich and V-rich films have different levels of structural distortion, with La-rich (V-rich) films showing a larger (smaller) out-of-plane lattice parameter compared to what one would expect from epitaxial strain effects alone. Both types of films show deviation from the behavior of bulk LVO in optical measurement, i.e., they do not show signatures of the expected long range orbital order, which can be a result of the structural distortions or the presence of structural domains. In transport measurements, La-rich films display clear signatures of electronic phase separation accompanying a temperature induced metal-insulator transition, while V-rich films behave as Mott insulators. The out-of-plane lattice parameter plays a crucial role in determining the transport properties, as the crossover from Mott-insulating to disorder-induced phase-separated behavior occurs around a lattice parameter value of 3.96 Å, quite different from what has been previously reported.