沉积温度对BiFeO3薄膜的微观结构与化学计量比的影响

采用高分辨透射电子显微镜并结合选区电子衍射、X射线能谱仪技术研究沉积温度对BiFeO3薄膜的微观结构与化学计量比的影响。与600℃和700℃沉积的BiFeO3薄膜相比,在500℃沉积的BiFeO3薄膜表面出现了许多岛状的二次相,即Bi2O3。当沉积温度提高到600℃和700℃时,外延BiFeO3薄膜是单晶,并且与SrRuO3缓冲层匹配良好,而且没有出现位错和二次相。通过大量的EDS数据统计分析,在500℃、600℃和700℃生长的BiFeO3薄膜,它们的Bi/Fe摩尔比分别为0.798、0.906和0.870,其中,Bi元素的缺乏可能是由于500℃时析出物Bi2O3的形成和700℃时Bi的挥发所致。

Effect of deposition temperature on microstructure and stoichiometric ratio of BiFeO3 thin films

The relationship of the microstructure and stoichiometry of BiFeO3(BFO) thin films with variable substrate temperatures was investigated by high resolution transmission electron microscope(HRTEM) combining with selected area electron diffraction(SAED) and X-ray energy dispersive spectrometer(EDS) techniques. Comparing with the flat surface of BFO films deposited at 600 ℃ and 700 ℃, many island-shaped secondary phases appear at the surface of BFO film deposited at 500 ℃, which are identified as Bi2O3. When the deposition temperature is increased to 600 ℃ and 700 ℃, the epitaxial BFO films are perfect single crystals matching well with SRO electrode layers without dislocation and secondary phases. Through statistical analysis of a large number of EDS data, the Bi/Fe molar ratios are 0.798, 0.906 and 0.870 for BFO films grown at 500 ℃,600 ℃ and 700 ℃, respectively. The deficiencies of Bi element are probably caused by the formation of Bi2O3 precipitates at 500 ℃ and the evaporation of Bi at 700 ℃.