Breckenfeld Eric, Chen Zuhuang, Damodaran Anoop R, Martin Lane W
Materials Science and Technology Division, Code 6364, Naval Research Laboratory , Washington, DC 20475, United States.
ACS Appl Mater Interfaces. 2014 Dec 24;6(24):22436-44. doi: 10.1021/am506436s. Epub 2014 Dec 2.
Next-generation devices will rely on exotic functional properties not found in traditional systems. One class of materials of particular interest for applications are those possessing metal-to-insulator transitions (MITs). In this work, we probe the relationship between variations in the growth process, subsequent variations in cation stoichiometry, and the MIT in NdNiO3 thin films. Slight variations in the growth conditions, in particular the laser fluence, during pulsed-laser deposition growth of NdNiO3 produces films that are both single-phase and coherently strained to a range of substrates despite possessing as much as 15% Nd-excess. Subsequent study of the temperature-dependence of the electronic transport reveals dramatic changes in both the onset and magnitude of the resistivity change at the MIT with increasing cation nonstoichiometry giving rise to a decrease (and ultimately a suppression) of the transition and the magnitude of the resistivity change. From there, the electronic transport of nearly ideal NdNiO3 thin films are studied as a function of epitaxial strain, thickness, and orientation. Overall, transitioning from tensile to compressive strain results in a systematic reduction of the onset and magnitude of the resistivity change across the MIT, thinner films are found to possess sharper MITs with larger changes in the resistivity at the transition, and (001)-oriented films exhibit sharper and larger MITs as compared to (110)- and (111)-oriented films as a result of highly anisotropic in-plane transport in the latter.
下一代器件将依赖于传统系统中不存在的奇异功能特性。一类特别受应用关注的材料是那些具有金属-绝缘体转变（MIT）的材料。在这项工作中，我们探究了NdNiO3薄膜生长过程中的变化、随后阳离子化学计量比的变化与MIT之间的关系。在NdNiO3的脉冲激光沉积生长过程中，生长条件的微小变化，特别是激光能量密度，会产生单相且与一系列衬底相干应变的薄膜，尽管这些薄膜的Nd过量高达15%。随后对电子输运的温度依赖性研究表明，随着阳离子非化学计量比的增加，MIT处电阻率变化的起始点和幅度都发生了显著变化，导致转变的减小（最终抑制）以及电阻率变化的幅度减小。从那里开始，研究了近乎理想的NdNiO3薄膜的电子输运随外延应变、厚度和取向的变化。总体而言，从拉伸应变转变为压缩应变会导致MIT处电阻率变化的起始点和幅度系统性降低，发现较薄的薄膜具有更尖锐的MIT，在转变时电阻率变化更大，并且由于后者具有高度各向异性的面内输运，与（110）和（111）取向的薄膜相比，（001）取向的薄膜表现出更尖锐和更大的MIT。
