Structural characterization of sputter-deposited LaNiO3 thin films on Si substrate by x-ray reflectivity and diffraction

X-ray reflectivity and diffraction were applied to characterize the highly (100)-textured thin films of LaNiO3, which were deposited on Si substrate via radio frequency magnetron sputtering at temperatures ranging from 250 to 450 degrees C. Two interference fringes of different period were observed from the reflectivity curves, and the fitting result indicates that in addition to the normal lanthanum-nickel oxide layer, a transition layer, which has a larger mass density than the previous one, exists in the sputter-deposited films. A comparison of the measured x-ray diffraction intensity with that calculated from layer thickness and mass density obtained from reflectivity data indicates that the transition layer is noncrystalline. The x-ray diffraction result also shows that there is a significant decrease of (100) diffraction intensity relative to that of (200) as increasing the deposition temperature. Using the reflectivity and diffraction data along with results of electron diffraction and film composition analysis from our other studies, such a change of relative intensity between the two diffraction peaks is attributed to the increasing content of two also highly textured La-rich phases, i.e., (110)-textured La4Ni3O10 and (100)-textured La2NiO4, in addition to the LaNiO3.