Structural characterization of sputter-deposited LaNiO 3 thin films on Si substrate by x-ray reflectivity and diffractio
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Structural characterization of sputter-deposited LaNiO3 thin films on Si substrate by x-ray reflectivity and diffraction Hsin-Yi Lee Department of Materials Science and Engineering, National Tsing Hua University, and Research Division, Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan, Republic of China
Tai-Bor Wu Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30043, Taiwan, Republic of China (Received 31 July 1996; accepted 4 November 1996)
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 ±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 La4 Ni3 O10 and (100)-textured La2 NiO4 , in addition to the LaNiO3 .
I. INTRODUCTION
The preparation of electrodes for ferroelectric thinfilm capacitors is crucial in fabricating the ferroelectric memories. Although Pt or Pt-based metal films are widely used, the weak adhesion to the Si substrates, the deterioration of ferroelectric properties by the outdiffusion of an interposed Ti layer, and unsatisfactory performance of capacitors against fatigue limit the practical applications of these materials as electrodes for ferroelectric thin-film capacitors.1–3 Alternatively, the conducting oxide layers, such as RuO2 , SrRuO3 , IrO2 , and La1–x Srx CoO3 , are considered as better choices for their significant improvement of the fatigue problem4–7 In particular, LaNiO3 has also attracted attention. It is a perovskite-type metallic oxide8–10 having the same type of structure as that of ferroelectric films, which provides a good crystallographic compatibility with the ferroelectric layers. Therefore, the LaNiO3 is also considered as a promising alternative for a Ptbased electrode. In a previous work, we were successful in preparing highly (100)-oriented LaNiO3 films on different substrates by the radio frequency magnetron sputtering method.11 These films are metallic and can be used
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