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Effect of substrate temperature on the structural, optical and electrical properties of dc magnetron sputtered tantalum oxide films

Chandra, Jagadeesh SV and Uthanna, S and Rao, Mohan G (2008) Effect of substrate temperature on the structural, optical and electrical properties of dc magnetron sputtered tantalum oxide films. In: Applied Surface Science, 254 (7). pp. 1953-1960.

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Abstract

dc reactive magnetron sputtering technique was employed for deposition of tantalum oxide films on quartz and silicon substrates by sputtering of pure tantalum target in the presence of oxygen and argon gases under various substrate temperatures in the range 303–973 K. The variation of cathode potential with the oxygen partial pressure was systematically studied. The influence of substrate temperature on the chemical binding configuration, crystal structure and optical properties was investigated. X-ray photoelectron spectroscopic studies indicated that the films formed at oxygen partial pressures \geq1 × $10^{-4}$ mbar were stoichiometric. The Fourier transform infrared spectroscopic studies revealed that the films formed up to substrate temperatures <673 K showed a broad absorption band at 750–1000 $cm^{-1}$ and a sharp band at 630 $cm^{-1}$ indicated the presence of amorphous phase while at higher substrate temperatures the appearance of bands at about 810 and 510 $cm^{-1}$ revealed the polycrystalline nature. The effect of substrate temperature on the electrical characteristics of $Al/Ta_2O_5/Si$ structure was investigated. The dielectric constant values were in the range 17–29 in the substrate temperature range of 303–973 K. The current–voltage characteristics showed modified Poole–Frenkel conduction mechanism with a tendency for reduction of the compensation level. The optical band gap of the films decreased from 4.44 to 4.25 eV and the refractive index increased from 1.89 to 2.25 with the increase of substrate temperature from 303 to 973 K.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Elsevier.
Keywords: Tantalum oxide; Dielectric; Optical; Electrical.
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 08 Mar 2008
Last Modified: 19 Sep 2010 04:43
URI: http://eprints.iisc.ernet.in/id/eprint/13345

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