Structure and Characterization of Sputtered Thin Films Based on Lead Titanate.
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STRUCTURE AND CHARACTERIZATION OF SPUTTERED THIN FILMS BASED ON LEAD TITANATE. A. PIGNOLET, P.E. SCHMID, L. WANG and F. LEVY Institute of Applied Physics, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland
ABSTRACT Pure and doped lead-titanate (PT) and lead-zirconate-titanate (PZT) thin films have been deposited on platinum-coated silicon by rf-magnetron sputtering from pressed powder targets. The films have been deposited without substrate heating. The amorphous films were then annealed in an oxygen flow. The structure of the films is tetragonal or rhombohedral depending on composition. The electrical resistivity, dielectric permittivity, ferroelectric hysteresis and pyroelectric coefficient are reported.
INTRODUCTION The macroscopic polarization of ferroelectric oxides has strong dependences on thermodynamic variables such as temperature, pressure or electric field giving rise to pyro-, piezo- and ferroelectricity. A great number of electronic applications based on these materials have been proposed. Thin films of ferroelectric oxides are very promising materials for a wide range of applications such as high-value capacitors [1], infrared sensors [2-6], ultrasonic sensors [7], non-volatile ferroelectric memories with low switching voltage [8-10] and various electro-optical devices [11, 12]. Recently the synthesis of thin films of ferroelectric oxides has been the subject of intense study [13-16]. Important materials under consideration include pure and doped lead titanate and lead zirconate-titanate (PZT). These materials exhibit a unique blend of electrical properties such as pyroelectricity, piezoelectricity, elasto-optic effect, linear and quadratic electro-optic effect. Many attempts have been carried out to prepare ferroelectric thin films by various methods such as ion plating, rf sputtering, ion beam sputtering, electron beam evaporation and chemical vapor deposition. Most of these films have been deposited on single-crystal substrates including SrTi0 3 , MgO or A120 3 [17-19]. However a better integration of ferroelectric films to microelectronic devices requires substrates compatible with silicon technology [20, 21]. We have studied the structural and electrical properties of pure and doped PbTi03 and PZT deposited on platinum-coated silicon by rf-magnetron sputtering. Polycrystalline films with a tetragonal or rhombohedral structure depending on composition were obtained by deposition without substrate heating followed by a post-deposition thermal treatment. The dielectric, ferroelectric and pyroelectric properties of these films have been investigated and are reported below.
EXPERIMENTAL PROCEDURE Thin films of PbTiO3 and PZT were deposited by rf-magnetron sputtering (NORDIKO system) onto platinum-covered (100) silicon and platinum-covered, thermally oxidized silicon (about 100 nm of Si0 2).
Mat. Res. Soc. Symp. Proc. Vol. 230. @1992 Materials Research Society
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The vacuum chamber was pumped down to 10-' Pa prior to film deposition and the optimized sputtering conditions are
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