Pulsed laser deposition of perovskite relaxor ferroelectric thin films N. Scarisoreanu a , M. Dinescu a, * , F. Craciun b , P. Verardi c , A. Moldovan a , A. Purice a , C. Galassi d a NILPRP, Lasers Department, Bucharest, P.O. Box MG-16, RO 077125, Romania b CNR-Istituto dei Sistemi Complessi, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy c CNR-Istituto di Acustica, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy d CNR-ISTEC, Via Granarolo 64, I 48018 Faenza, Italy Received 3 May 2005; accepted 18 July 2005 Available online 27 October 2005 Abstract Structural, dielectric and ferroelectric properties of thin films of La-doped lead zirconate titanate (PLZT) and sodium bismuth titanate–barium titanate (NBT–BT) perovskite relaxor ferroelectric have been investigated. PLZT films were deposited on Pt/Si substrates in oxygen atmosphere by pulsed laser deposition (PLD) and radio frequency (RF) discharge-assisted PLD, using sintered targets with different La content and Zr/Ti ratio, near or at the boundary relaxor ferroelectric. The films are polycrystalline with perovskite cubic or slightly rhombohedral structure. A slim ferroelectric hysteresis loop, typical for relaxors, has been measured for all film sets. Dielectric characterization shows a large value of capacitance tunability and low dielectric loss. However, common problems related to lead diffusion into the metallic electrode layer do not allow one to obtain high capacitance values, due to the formation of an interface layer with low dielectric constant. Lead-free NBT–BT thin films have been deposited on single crystal (1 0 0)-MgO substrates starting from targets with composition at the morphotropic phase boundary between rhombohedral and tetragonal phase. Films deposited by PLD are polycrystalline perovskite with a slight (1 0 0) orientation. Capacitance measurements were performed using interdigital metallic electrodes deposited on the film’s top surface and showed high relative dielectric constant, on the order of 1300. # 2005 Elsevier B.V. All rights reserved. Keywords: PLZT films; NBT–BT films; Perovskite; Relaxor ferroelectric films 1. Introduction Perovskite ferroelectric materials are intensively studied due to their high dielectric, piezoelectric electrooptical and electrostrictive constants [1,2]. Among these, lead zirconate titanate (PZT) is the most investigated and used both in bulk and thin film forms. By changing the ratio Zr/Ti its structure changes from orthorhombic to rhombohedral and tetragonal and thus allows tailoring to a wide range of physical properties. Moreover, the substitution of some impurities, such as La, allows a gradual change from the ferroelectric phase to a pseudocubic relaxor phase [2]. Relaxor ferroelectric materials are characterized by the absence of long-range correlations typical of ferroelectrics and the existence of a short range order at the level of ferroelectric nanodomains. Macroscopically, this feature manifests itself through the absence of a well-defined transition temperature between the ferroelectric and para- electric phases and through the appearance of a very broad peak of the dielectric constant maximum, which shifts to a much lower temperature. These relaxors are generally tailored to exhibit this maximum near room temperature, thus giving very large dielectric, electrostrictive and electro-optical coefficients at a handy temperature range. In previous studies the growth of these materials in thin films has been performed by different techniques [3] and good results have been also obtained by employing pulsed laser deposition (PLD) [4]. In this paper, we investigate the structural, dielectric and ferroelectric properties of La-doped PZT (PLZT) thin films with different La content and Zr/Ti ratio, near or at the boundary relaxor ferroelectric. Film synthesis has been performed both by PLD and by radio www.elsevier.com/locate/apsusc Applied Surface Science 252 (2006) 4553–4557 * Corresponding author. Tel.: +40 214574470; fax: +40 214231791. E-mail address: dinescum@ifin.nipne.ro (M. Dinescu). 0169-4332/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2005.07.140