Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200241, People's Republic of China.
ACS Appl Mater Interfaces. 2010 Mar;2(3):896-902. doi: 10.1021/am900868a.
La(0.5)Sr(0.5)CoO(3) (LSCO) nanocrystalline (nc) films have been directly grown on silicon wafers under different substrate temperatures by pulsed laser deposition. The X-ray diffraction analysis indicate that the films are polycrystalline with the pure perovskite phase at higher substrate temperatures. The columnar growth formation with the nanocrystalline structure in the films has been confirmed by microscopy experiments. Infrared-ultraviolet optical properties of the LSCO films have been investigated with the aid of spectroscopic ellipsometry (SE). Dielectric function in the photon energy range of 1.1-3.1 eV (400-1100 nm) has been extracted by reproducing the experimental data with a Lorentz oscillator model. It is found that the real part is decreased from 4.7 to -0.7 at the near-infrared region with increasing substrate temperature. The optical conductivity shows a different variation trend for the lower and higher growth temperatures, respectively. Note that the films deposited above 650 degrees C exhibit the well-defined metallic phase behavior. The discrepancies could be mainly ascribed to different crystalline structure and surface morphology. The present results may be crucial for future applications of ferromagnetic-based optoelectronic and spin-electronic devices.
La(0.5)Sr(0.5)CoO(3)（LSCO）纳米晶薄膜通过脉冲激光沉积直接在硅片上生长，沉积温度不同。X 射线衍射分析表明，在较高的衬底温度下，薄膜为多晶态，具有纯钙钛矿相。通过显微镜实验证实了薄膜中具有柱状生长形态和纳米晶结构。利用光谱椭圆偏振术（SE）研究了 LSCO 薄膜的红外-紫外光学性质。通过洛伦兹振子模型再现实验数据，提取了光子能量范围为 1.1-3.1 eV（400-1100nm）的介电函数。结果表明，随着衬底温度的升高，近红外区域的实部从 4.7 减小到-0.7。光学电导率在较低和较高生长温度下呈现出不同的变化趋势。需要注意的是，沉积温度高于 650°C 的薄膜表现出明显的金属相行为。这些差异主要归因于不同的晶体结构和表面形貌。本研究结果对于铁磁基光电和自旋电子器件的未来应用可能至关重要。
