Date of Graduation

Summer 2009


Master of Science in Materials Science


Physics, Astronomy, and Materials Science

Committee Chair

Pawan Kahol


capacitors, dielectric constant, leakage current, pulsed laser deposition, strontium titanate oxide, capacitance

Subject Categories

Materials Science and Engineering


High dielectric materials have the potential to provide tremendous storage capacity for applications in non-volatile memory devices. However, one of the major difficulties in using high dielectric materials is high leakage current. Materials that have low leakage current also have low dielectric constant. An attempt has been made in this work to have control over the leakage current by combining high dielectric and low dielectric materials. Specifically, we have prepared composites of strontium titanate oxide (STO), and silicon dioxide (SiO2), which have dielectric constants of 310 and 4.5 respectively. Both these materials were combined with varying amounts of SiO2. Samples of pure STO and SiO2 were also made to compare the properties of the composites, which were in the form of pellets. Thin films of pure STO and 95 % STO were prepared using pulsed laser deposition technique (PLD). X-ray diffraction studies were done to optimize the growth conditions such as thickness, temperature, and oxygen annealing. Electrical measurements were made for capacitance and dissipation loss. Current-voltage measurements were made to determine the amount of leakage current in all the samples. Our measurements indicate that the presence of SiO2 up to 10% in STO pellet reduces the leakage current by an order of magnitude of 10 (6 x 10-8A to 5 x 10-9A). All the samples were also analyzed using Cole-Cole plots, where pure STO and SiO2 pellets exhibit single relaxation behavior. The composites indicate the presence of more than one relaxation process, which cannot clearly be established due to the limitations of the instrument to go beyond 1 MHz. Presence of multi-relaxations in the composite materials is speculated to be due to the segregation of STO and SiO2 in the composites. In summary, these investigations reveal that the addition of SiO2 to STO reduces leakage current, but still gives a material which has a relatively high dielectric constant.


© Yogini Girish Dhopade

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