Crystallization kinetics of sputter-deposited LaNiO 3 thin films on Si substrate
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Crystallization kinetics of sputter-deposited LaNiO3 thin films on Si substrate Hsin-Yi Lee Research Division, Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan, Republic of China, and Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30043, 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 August 1997; accepted 5 November 1997)
The kinetics of in situ crystallization of LaNiO3 thin films in sputtering deposition at temperatures ranging from 250 to 450 ±C and isothermal crystallization of room-temperature (RT) sputtered LaNiO3 thin films in annealing at 350 –500 ±C were investigated by the x-ray diffraction method. The crystallization in both cases basically followed the Johnson–Mehl–Avrami (JMA) relation. However, different crystallization kinetics were observed. The transformation index and activation energy of crystallization in high temperature sputtering were about 1.5 and 33 kJymole, respectively, while in the annealing of RT-sputtered films, 1.0 and 63 kJymole were found. From the determined transformation index, it is suggested that the crystallization rate in high temperature sputtering was determined by a diffusion-controlled process of lateral growth with a decreasing nucleation rate of crystallites in the adsorption layer. However, the annealed films crystallized by an interface-controlled and one-dimensional growth of existing nuclei.
I. INTRODUCTION
In recent years, the electrodes for ferroelectric thinfilm capacitors received considerable attention in the fabrication of ferroelectric memories. Although Pt or Ptbased metal films are wildly 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 For this reason, conducting oxide layers, such as RuO2 , SrRuO3 , IrO2 , and La12x Srx CoO3 , have been studied extensively as alternative electrodes. Most electrodes using these materials effectively solve the problem of fatigue.4–7 The LaNiO3 (LNO), which is a perovskite-related Pauli paramagnetic and metallic oxide down to 0.4 K,8–10 has also attracted some attention in the past few years. Since LNO has the same type of perovskite structure as that of most ferroelectric films with little lattice mismatch, it provides a good crystallographic compatibility with the ferroelectric layers. A better bonding between these ferroelectric materials and the LNO layer can be expected. Therefore, the LaNiO3 is also a promising alternative for Pt-based electrode. Successful preparation of epitaxial or textured LNO thin films on (100)oriented substrates of LaAlO3 , SrTiO3 , and YSZ have been achieved via pulsed laser deposition,11 and on J. Mater. Res., Vol. 1
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