Dielectric Studies of laser ablated Ca doped BaTiO 3 thin films.
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U12.15.1
Dielectric Studies of laser ablated Ca doped BaTiO3 thin films. P.Victor, R.Ranjith, Asis Sarkar, R.Vinayak,1 S.Saha 2 and S.B.Krupanidhi, Materials Research Center, Indian Institute of Science, Bangalore, India 1 Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay, India 2 Materials Science division, Argonne National Laboratory, Argonne, IL, USA. Abstract Recently, there has been growing interest in Ca modified BaTiO3 structures due to their larger electro-optic coefficients for their use in optical storage of information over conventional BaTiO3 crystals. Barium Calcium Titanate (BCT) shows promising applications in advanced laser systems, optical interconnects and optical storage devices. BaTiO3 thin films of varied Ca (3 at. % - 15 at. %) doping were deposited using pulsed laser ablation (KrF excimer laser) technique over Pt/Si substrates. The stoichiometric and the compositional analysis were carried out using EDAX and SIMS. The dielectric studies were done at the frequency regime of 40 Hz to 100 kHz at different ambient temperatures from 200 K to 600 K. The BCT thin films exhibited diffuse phase transition, which was of a typical non lead relaxor behavior and had high dielectric constant and low dielectric loss. The phase transition for the different compositions of BCT thin films was near the room temperature, showing a marked departure from the bulk phase transition. The C - V and the hysteresis behavior confirmed the ferroelectric nature below the phase transition and paraelectric at the room temperature. INTRODUCTION Perovskite structure ferroelectrics have been gaining technological importance because of its essential use in the micro electromechanical systems (MEMS), memory devices and microwave applications. [1 – 3] In specific, barium titanate and dopants incorporated BaTiO3 had been promising because of its potential use in the applications for the microwave communications.[4] Doping of the Ca in the BaTiO3 (denoted as BCT) ceramics had showed a remarkable improvement in the electromechanical behavior, increase in the temperature range of the stability of the tetragonal phase and inhibited the formation of the unwanted hexagonal phase of BaTiO3. On doping the Ca in the BaTiO3 ceramics, Ca 2+ acts as a reduction inhibitor. Han et.al.,[5] and Zhang et. al.,[6] suggested that there is a possibility of the Ca2+ ions to partially occupy the Ti sites in the BaTiO3 lattice. It gives rise to a doubly charged acceptor center Ca”Ti , which compensates the oxygen vacancies formed during sintering in a reducing atmosphere and resulted in the formation of high resistivity dielectrics. To the authors knowledge, there had been little effort on the processing and electrical characterization on BCT thin films, hence, we report the electrical and structural characterization on the laser ablated BCT thin films with varied calcium content.
U12.15.2
EXPERIMENT Ba1-xCaxTiO3 (x = 0.05 (denoted as B5CT), 0.1 (denoted as B10CT) , 0.15 at. % (denoted as B13CT) targ
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