Impact of Template Layers on Dielectric and Electrical Properties of Pulsed-Laser Ablated Pb(Mg 1/3 Nb 2/3 )O 3 - PbTiO
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Impact of Template Layers on Dielectric and Electrical Properties of Pulsed-Laser Ablated Pb(Mg1/3 Nb2/3)O3 - PbTiO3 Thin Films Apurba Laha, S. Saha 1 and, S. B. Krupanidhi Materials Research Centre, Indian Institute of Science, Bangalore -560 012, INDIA 1 Materials Science Division Argonne National Laboratory, 9700, S. Cass Avenue, Argonne, IL-60439, USA
ABSTRACT A study was done on pulsed laser deposited relaxor ferroelectric thin films of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) deposited on platinized silicon substrates with template layers to observe the influence of the template layers on physical and electrical properties. Initial results, showed that perovskite phase (80% by volume) was obtained through proper selection of the processing conditions on Pt/Ti/SiO2/Si substrates. The films were grown at 300oC and then annealed in a rapid thermal annealing furnace in the temperature range of 750850oC to induce crystallization. Comparison of the films annealed at different temperatures revealed a change in crystallinity, perovskite phase formation and grain size. These results were further used to improve the quality of the perovskite PMN-PT phase by inserting thin layers of TiO2 on the Pt substrate. These resulted in an increase in perovskite phase in the films even at lower annealing temperatures. Dielectric studies on the PMN-PT films show very high values of dielectric constant (1300) at room temperature, which further improved with the insertion of the template seed layer. The relaxor properties of the PMN-PT were correlated with Vogel-Fulcher theory to determine the actual nature of the relaxation process.
INTRODUCTION Solid solution of xPb(Mg1/3Nb2/3)O3-(1-x)PbTiO3 (PMN-PT) is a well known relaxor ferroelectric material [1,2], possessing very high dielectric constant and has recently received attention for its potential application in thin film capacitors [3], mechanical actuators and transducers [4-6]. With the addition of PT in the composition a modification of the transition temperature is easy, thereby making it suitable for various applications. Further the relaxor property in PMN-PT induces a broad transition near room temperature, specifically known as a diffuse phase transition with a very high dielectric constant over a large temperature range. However, the growth and processing of PMN-PT thin films has remained an important task, due its tendency towards forming a pyrochlore phase characterized by a very low dielectric constant. Earlier reported work as done by Tantigate et al. [7] and others [8,9], state the difficulty in the perovskite phase formation on platinum coated silicon substrates. The difficulty arises due to the difference in surface texture of Pt layer and in maintaining the correct stoichiometric ratio of the cations, for example, excess Pb in the film reacts with Nb to form the pyrochlore phase [10]. C7.28.1
Hence most of the work reported in the literature has adhered to the usage of substrates other than platinum or the use of template layers to aid the perovskite phase formati
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