Substrate bias voltage influenced structural, electrical and optical properties of dc magnetron sputtered Ta2O5 films |
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Authors: | S V Jagadeesh Chandra M Chandrasekhar G Mohan Rao S Uthanna |
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Affiliation: | (1) Department of Physics, Sri Venkateswara University, Tirupati, 517 502, India;(2) Department of Instrumentation, Indian Institute of Science, Bangalore, 560 012, India |
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Abstract: | Tantalum oxide (Ta2O5) films were formed on silicon (111) and quartz substrates by dc reactive magnetron sputtering of tantalum target in the presence
of oxygen and argon gases mixture. The influence of substrate bias voltage on the chemical binding configuration, structural,
electrical and optical properties was investigated. The unbiased films were amorphous in nature. As the substrate bias voltage
increased to −50 V the films were transformed into polycrystalline. Further increase of substrate bias voltage to −200 V the
crystallinity of the films increased. Electrical characteristics of Al/Ta2O5/Si structured films deposited at different substrate bias voltages in the range from 0 to −200 V were studied. The substrate
bias voltage reduced the leakage current density and increased the dielectric constant. The optical transmittance of the films
increased with the increase of substrate bias voltage. The unbiased films showed an optical band gap of 4.44 eV and the refractive
index of 1.89. When the substrate bias voltage increased to −200 V the optical band gap and refractive index increased to
4.50 eV and 2.14, respectively due to the improvement in the crystallinity and packing density of the films. The crystallization
due to the applied voltage was attributed to the interaction of the positive ions in plasma with the growing film. |
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