Nanoscale crystal imperfection-induced characterization changes of manganite nanolayers with various crystallographic te
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NANO EXPRESS
Open Access
Nanoscale crystal imperfection-induced characterization changes of manganite nanolayers with various crystallographic textures Yuan-Chang Liang*, Hua Zhong and Wen-Kai Liao
Abstract (La,Sr)MnO3 (LSMO) nanolayers with various crystallographic textures were grown on the sapphire substrate with and without In2O3 epitaxial buffering. The LSMO nanolayer with In2O3 epitaxial buffering has a (110) preferred orientation. However, the nanolayer without buffering shows a highly (100)-oriented texture. Detailed microstructure analyses show that the LSMO nanolayer with In2O3 epitaxial buffering has a high degree of nanoscale disordered regions (such as subgrain boundaries and incoherent heterointerfaces) in the film. These structural inhomogeneities caused a low degree of ferromagnetic ordering in LSMO with In2O3 epitaxial buffering, which leads to a lower saturation magnetization value and Curie temperature, and higher coercivity and resistivity. Keywords: Crystallographic texture; Manganite; Epitaxy; Magnetic properties; Buffering
Background Because of their versatile physical properties, various transition metal oxides, specifically perovskite-based manganites, have attracted considerable scientific and technological attention [1-3]. There is potential for the application of La1 − xSrxMnO3 (LSMO) in the magnetic storage device and spin-sensitive device field, or it can be used as an important hole-doping material to construct microelectronic devices [2,4,5]. To realize nanodevice applications with high efficiency, it is imperative that LSMO thin films be fabricated on a nanometric scale. High-quality epitaxial manganite films with specific orientations are essential for the next-generation of microelectronic and magnetic devices. However, singlecrystalline perovskite oxide substrates are expensive, and a large diameter substrate is currently technologically unavailable. These factors hinder the practical application of epitaxial LSMO films in the electronic industry [4,6]. Two factors might cause lattice stress in nanoscale manganite thin films. An ultra-thin LSMO epilayer grown on the lattice-mismatched perovskite oxide substrate usually induces built-in stresses in the film, which greatly affect its physical properties [4,7-9]. * Correspondence: [email protected] Institute of Materials Engineering, National Taiwan Ocean University, Keelung 20224, Taiwan
Moreover, a large thermal expansion coefficient (TEC) difference between the film and substrate also significantly affects the lattice stress in nanoscale manganite thin films. In comparison to randomly oriented thin films, the highly crystallographic textured film usually exhibits superior crystal quality. If the TEC value of a substrate and film is similar, then highly textured ultra-thin polycrystalline LSMO films would not suffer from the lattice distortion that was caused by a lattice mismatch on the single crystalline substrates. This might be promising for practical applications in devices. The sapphire substrate and LSMO have simil
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