退火温度对La_(0.8)Bi_(0.2)MnO_3(LBMO)薄膜结构及性质的影响

Influence of Annealing on Structure and Properties of La_(0.8)Bi_(0.2)MnO_3(LBMO) Thin Films

用射频磁控溅射方法在Si[100]衬底上沉积了La0.8Bi0.2MnO3多晶薄膜,再在不同温度下进行退火热处理.使用XRD衍射仪、原子力显微镜(AFM)分别对薄膜微结构进行了表征,结果显示薄膜随着退火温度的升高逐渐晶化,晶体结构属于钙钛矿菱形结构;薄膜的表面致密、晶粒大小均匀,850℃退火的薄膜晶粒尺寸约40 nm左右.薄膜的X射线光电子能谱(XPS)测量表明薄膜中Bi的价态为Bi3+和Bi5+.经过退火的薄膜在室温300 K、液氮77 K下都存在巨磁电阻效应.850℃退火的薄膜,温度为300 K和77 K、磁场为1.5 T条件下,磁电阻分别达到22.50%和26.98%.

By using RF magnetosputtering technique,La0.8Bi0.2MnO3 thin films were fabricated on Si[100] substrates. Then these films were annealed at different temperatures,and characterized by X-ray diffraction and Atomic Force Microscope （AFM）. The results showed that the crystal structure of the film is rhombohedral. The surface of thin films was dense,and the grain size of thin films, which had uniform particles, annealed at 850 ℃ was about 40 nm. The valence state of bismuth （doped element ）was confirmed by XPS measurements. The results show that Bi mainly exists Bi^3＋and Bi^5＋valence state forms. The thin films after annealing have a giant magnetoresistance （GMR） effect at room temperature 300 K and liquid nitrogen 77 K. The value of MR of the thin film annealed at 850 ℃ at 1.5 T is 22.50% at 300 K,and 26.98% at 77 K,respectively.