La_(0.7)Ca_(0.3)MnO_3簿膜的掠入射X射线衍射研究

Grazing incidence X-ray diffraction study of La_(0.7)Ca_(0.3)MnO_3 film

利用90°离轴射频磁控溅射方法将La_(0.7)Ca_(0.3)MnO_3(LCMO)沉积于(001)取向的SrTiO_3(STO)、MgO和α-Al_2O_3(ALO)单晶基片上,薄膜厚度均为500A。通过掠入射X射线衍射技术测量了LCMO薄膜的横向晶格常数(即面内晶格常数),结合常规X射线衍射研究了LCMO薄膜的晶格应变及其弛豫情况。结果表明,LCMO薄膜在MgO和ALO基片上的应变弛豫临界厚度很小,这可能与薄膜—基片之间高的晶格失配率有关。LCMO薄膜的应变弛豫与四方畸变的弛豫可能具有不同的机制。利用掠入射X射线衍射对LCMO薄膜面内生长取向的研究给出了与利用电子显微技术研究相同的结果。

La_(0.7)Ca_(0.3)MnO_3(LCMO) thin films with the thickness of 500 A were deposited on(001)-oriented single crystal SrTiO_3(STO), MgO and α-Al_2O_3(ALO) by 90° off-axis radio frequency magnetron sputtering. Grazing incidence X-ray diffraction technique, associated with normal X-ray diffraction, was adopted to measure the in-plane lattice parameter and investigate the lattice strain and strain relaxation in LCMO films. The results indicate that critical thickness of strain relaxation is very small, which may be related to large mismatch between film and substrate. The mechanism for strain relaxation in LCMO film is perhaps different from that for tetragonal distortion. Furthermore, the in-plane growth orientation of LCMO film on STO and MgO was also studied by grazing incidence X-ray diffraction and the result is consistent with that from transmission electron microscopy.