Room-temperature spectroscopic ellipsometry data has been analyzed to determine the complex dielectric functions, ε(E) = ε1(E) + iε2(E) of as-deposited Sb-doped ZnO (SZO) thin films grown on n-Si(100) substrates by dual ion beam sputtering deposition system for different growth temperatures (Tg). The dielectric functions have been obtained from ellipsometry data analyses using Cody-Lorentz oscillator in the GenOsc model. A gradual reduction in the value of electron concentration and finally the conversion of doping characteristics from donor type to acceptor type was observed with the rise in Tg. This, in turn, resulted in the decline of broadening of ε1 peaks, and hence in the increase of excitonic lifetime. Optical band-gap energy was observed to decrease with increase in Tg from 200 to 300 °C, and then rise continuously with further increase in Tg. X-ray diffraction measurements showed that all SZO films had (002) preferred crystal orientation. Hall measurement and X-ray photoelectron spectroscopy analysis confirmed that the change in the electrical conduction from n-to p-type was due to the enhancement in the value of Sb5+/Sb3+ ratio and SbZn-2VZn complex formation in SZO films.
Bibliographical noteFunding Information:
This work is partially supported by Department of Science and Technology (DST) Fast Track Scheme for Young Scientist No. SR/FTP/ETA-101/2010 and Project No. 37(3)/14/20/2014-BRNS by Board of Research in Nuclear Sciences (BRNS), Department of Atomic Energy (DAE), Government of India. This work is also supported by DST Science and Engineering Research Board (SERB) project number SR/S3/EECE/0142/2011 and Council of Scientific and Industrial Research (CSIR) project number 22(0608)/12/EMR-II. Authors thank to T. Shripathi and U. P. Deshpande of University Grants Commission Department of Atomic Energy (UGC, DAE) Consortium for Scientific Research, Indore for their help in recording XPS data. We are also grateful to DIBSD facility equipped at Sophisticated Instrument Centre (SIC) at IIT Indore.
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- Spectroscopic ellipsometry