Thickness dependent electrical properties of CdO thin films prepared by spray pyrolysis method |
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Authors: | L C S Murthy K S R K Rao |
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Affiliation: | (1) Department of Physics, Bangalore University, 560 056 Jnanabharathi, Bangalore, India;(2) Department of Physics, Indian Institute of Science, 560 012 Bangalore, India |
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Abstract: | A large number of thin films of cadmium oxide have been prepared on glass substrates by spray pyrolysis method. The prepared
films have uniform thickness varying from 200–600 nm and good adherence to the glass substrate. A systematic study has been
made on the influence of thickness on resistivity, sheet resistance, carrier concentration and mobility of the films. The
resistivity, sheet resistance, carrier concentration and mobility values varied from 1·56–5·72×10−3 Ω-cm, 128–189 Ω/□, 1·6–3·9×1021 cm−3 and 0·3–3 cm2/Vs, respectively for varying film thicknesses. A systematic increase in mobility with grain size clearly indicates the reduction
of overall scattering of charge carriers at the grain boundaries. The large concentration of charge carriers and low mobility
values have been attributed to the presence of Cd as an impurity in CdO microcrystallites. Using the optical transmission
data, the band gap was estimated and found to vary from 2·20–2·42 eV. These films have transmittance around 77% and average
reflectance is below 2·6% in the spectral range 350–850 nm. The films aren-type and polycrystalline in nature. SEM micrographs of the CdO films were taken and the films exhibit clear grains and grain
boundary formation at a substrate temperature as low as 523 K. |
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Keywords: | Spray pyrolysis CdO thin films structure and morphology II– VI semiconductor optical properties energy gap |
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