Growth and study of BaZrO 3 thin films by pulsed excimer laser ablation
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Growth and study of BaZrO3 thin films by pulsed excimer laser ablation V. Rajasekarakumar, P. Victor, R. Ranjith S. Saha1 S. Rajagopalan,2 A. K. Tyagi2 and S. B. Krupanidhi Materials Research Center, Indian Institute of Science, Bangalore- 560 012, India. 1 Argonne National Laboratory, Argonne, IL, USA. 2 Materials Science Division, IGCAR, Kalpakkam, India. ABSTRACT Thin films of BaZrO3 (BZ) were grown using a pulsed laser deposition technique on platinum coated silicon substrates. Films showed a polycrystalline perovskite structure upon different annealing procedures of in-situ and ex-situ crystallization. The composition analyses were done using Energy dispersive X-ray analysis (EDAX) and Secondary ion mass spectrometry (SIMS). The SIMS analysis revealed that the ZrO2 formation at the right interface of substrate and the film leads the degradation of the device on the electrical properties in the case of ex-situ crystallized films. But the in-situ films exhibited no interfacial formation. The dielectric properties have been studied for the different temperatures in the frequency regime of 40 Hz to 100kHz. The response of the film to external ac stimuli was studied at different temperatures, and it showed that ac conductivity values in the limiting case are correspond to oxygen vacancy motion. The electrical modulus is fitted to a stretched exponential function and the results clearly indicate the presence of the non-Debye type of dielectric relaxation in these materials. INTRODUCTION Presently there had been demand for monolithic microwave integrated circuit technologies (MMIC) for its essential use in the microwave communication applications, such as mobile phones, satellite communications and global positioning systems.1,2,3,4 The improved characteristics, reduction of sizes, and compatibility with existing circuits of microwave dielectric components are necessary for the miniaturization of integrated circuitry. In general, the materials utilized for these devices are paraelectric.5 The materials used as resonators and filters in microwave circuits require high dielectric constants, low dielectric losses (tanδ), and low temperature coefficient of resonance frequency (τf).6 Since 1970’s, in bulk several materials including BaZrO3 have been developed for their use in the microwave applications.7 There had been limited work on the BaZrO3 (BZ) thin films and the added advantage of BZ is that it has higher dielectric constant in the microwave frequency regime and are used as the substrates8 in the microwave circuits. The emphasis of the research reported here was to investigate the interface and ac electrical properties of the BZ thin films. EXPERIMENTAL DETAILS Polycrystalline BZ thin films were grown using a pulsed laser ablation technique using a KrF excimer laser. The base pressure was brought down to 2 x 10-6 Torr, and the pressure during deposition was kept at 20 mTorr by allowing oxygen into the deposition chamber. A dense, single phase BZ ceramic was used as a target. A fluence of 4 J/ cm2 was mainta
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