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Vol. 128, Issue 5, May 2011, pp.100-114




New Method for Fabrication of Co3O4 Thin Film Sensors: Structural, Morphological and Optoelectronic Properties


aVikas Patil, aShailesh Pawar, aManik Chougule, aBharat Raut, aRamesh Mulik, bShashwati Sen

aMaterials Research Laboratory, School of Physical Sciences, Solapur University,

Solapur-413255, M. S., India

b Crystal Technology Section, Bhabha atomic Research Centre, Mumbai, India

E-mail: drvbpatil@gmail.com



Received: 16 April 2011   /Accepted: 20 May 2011   /Published: 28 May 2011


Abstract: Nanocrystalline Co3O4 thin films have been deposited by spin coating technique and then have been analyzed to test their application in NH3 gas-sensing technology. In particular, spectrophotometric and conductivity measurements have been performed in order to determine the optical and electrical properties of Co3O4 thin films. The structure and the morphology of such material have been investigated by X ray diffraction and Scanning electron microscopy.


The X-ray diffraction studies confirmed that the films grown by this technique have good crystalline cubic spinel structure and present a random orientation. The morphology of the sol gel derived Co3O4 shows nanocrystalline grains with some overgrown clusters .The optical band gap has been determined from the absorption coefficient. We found that the optical band gap energy decreases from 2.58 eV to 2.07 eV with increasing annealing temperature between 400-700 oC. These mean that the optical quality of Co3O4 films is improved by annealing.


The dc electrical conductivity of Co3O4 thin films were increased from 10-4 to 10-2(Ω cm)-1 with increase in annealing temperature. The electron carrier concentration (n) and mobility (μ) of Co3O4 films annealed at 400-700 oC were estimated to be of the order of 2.4 to 4.5 x 1019 cm-3 and 5.2 to 7.0 x 10-5 cm2 V-1 s-1 respectively. It is observed that Co3O4 thin film annealing at 700 oC after deposition provide a smooth and flat texture suited for optoelectronic applications. Gas sensing properties showed that the Co3O4 films (at 700 oC) were sensitive as well as fast in responding to NH3. A high sensitivity for ammonia indicates that the Co3O4 films are selective for this gas.


Keywords: Co3O4 sensor, Structural properties, Optical properties, Electrical properties


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