Ca^(2+)掺杂对BiFeO_3薄膜结构及光学特性的影响

Effect of Ca Doping on Structure and Optical Properties in Multiferroic BiFeO_3 thin Films

采用溶胶凝胶法制备Bi1-xCaxFeO3前驱体溶液,利用旋涂的方法在ITO导电玻璃上制备Bi1-xCaxFeO3薄膜样品.用X-射线衍射仪、分光光度计分别对薄膜样品的晶体结构、透射光谱进行测量并利用透射光谱计算出材料的能带带隙.结果表明:所有Bi1-xCaxFeO3样品的主衍射峰与BiFeO3相吻合,具有较好的结晶度和良好的晶体结构,随着Ca2+掺杂量的增加,使BiFeO3样品的主衍射峰(104)与(110)逐渐成为单相峰(110),当Ca2+掺杂量大于0.05时,样品由斜六面体转变为正方晶系.所有样品在430nm^600nm区间形成陡峭的线性吸收边,随着Ca2+掺杂量的增加,吸收峰会发生红移.Ca2+掺杂能提高BiFeO3薄膜在可见光的吸收率.Ca2+掺杂导致BiFeO3薄膜带隙降低的主要原因是样品中的缺陷的数量、表面粗糙度及晶格结构共同作用的结果.

Multiferroic Bi 1-x CaxFeO3 thin films were deposited on ITO coated glass substrates by sol-gel method and spin coating technique. The X-ray diffraction analysis reveals that Bi 1-x Cax FeO3 thin films possessed the single-phase perovskite structure with rhomhohedral symmetry for all samples. The main diffraction peak between （104） and （110） of BiFeO3 samples overlaped （110） to single peak with increasing x, implying that rhombohedral symmetry has transformed to orthorhomhic perovskite structure. All samples were formed in the range of 430 nm-600 nm steep linear absorption edge, with the increase of x, and the spectral red shift of the absorption summit. With the increase of x, the band gap of BiFeO3thin film showed a decreasing trend. The band gap of BiFeO3 thin films is minimum of 2.15 eV for x=0.2.