Effect of oxygen partial pressure on texture development in lead zirconate titanate thin films processed from metalorgan
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Effect of oxygen partial pressure on texture development in lead zirconate titanate thin films processed from metalorganic precursors Jarrod L. Norton, Gerald L. Liedl, and Elliott B. Slamovich School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907-1289 (Received 12 April 1999; accepted 7 September 1999)
Metalorganic liquid precursors were used to examine the effects of processing atmosphere on texture development in oriented Pb(Zr0.60Ti0.40)O3 thin films. After removal of organic ligands via pyrolysis, the films were heated at 25 °C/min in a 5% H2/Ar atmosphere until a switching temperature, after which the atmosphere was switched to pure oxygen. The films were heated to a maximum temperature of 650 °C with switching temperatures ranging from 450 to 600 °C. The degree of (111) orientation in the lead zirconate titanate (PZT) films increased with increasing switching temperature, resulting in highly textured (111) PZT films. These results suggest that atmosphere control plays a significant role in texture development during rapid thermal processing.
I. INTRODUCTION
Lead zirconate titanate [Pb(ZrxTi1−x)O3 or PZT] ceramics are used for applications ranging from microactuators and transducers to ferroelectric memories.1 The ferroelectric properties of PZT are anisotropic; therefore, controlling thin film texture is a key requirement to optimize device performance. For rhombohedral PZT (x > 0.53), the remanent polarization is maximized by orienting the [111] crystallographic direction [a (111) texture] normal to the film surface, such that the applied electric field is parallel to the [111] direction. For tetragonal PZT (x < 0.53), a (100) texture will maximize film remanent polarization. A broad base of literature now exists addressing the control of preferred orientation of PZT thin films derived from metalorganic precursors. Film texture is controlled through the use of metalorganic decomposition (MOD) and sol-gel processes, coupled with rapid thermal processing (RTP).2–10 RTP involves high heating rates, generally achieved by placing a sample in a furnace already at the desired processing temperature, and has been used by a number of groups to process (111)- and (100)oriented PZT thin films. Reviewing the existing literature reveals that separate groups using very similar processing parameters have obtained conflicting results. For example, work by Aoki et al.2 showed that when thin films of metalorganic PZT precursors were first heated in air at 480 °C and then fired at 650 °C for 10 min, (111)textured PZT films were obtained. Skipping the 480 °C heating step resulted in a (100) texture. However, similar experiments by Chen and Chen3–5 gave the opposite reJ. Mater. Res., Vol. 14, No. 12, Dec 1999
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sult. PZT films heated with an intermediate step at 450 °C before firing to 700 °C yielded a (100) texture, while films heated directly to 625 °C had a (111) texture. Investigating possible m
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