Effect of Mg content on structural, electrical and optical properties of Zn1-xMgxO nanocomposite thin films

We report on the growth of Zn1-xMgxO (ZMO) thin films on quartz substrate using pulsed laser deposition (PLD) technique. The influence of varying Mg composition on structural, electrical and optical properties of ZMO films has been systematically investigated. Increase in Mg content (in the range 0.0 <= x <= 1.0), reflects the structural phase transition from wurtzite via mixed phase region to cubic one. X-ray diffraction (XRD) studies indicate the hexagonal wurtzite phase at Mg composition ranging from 0% to 30%; mixture of wurtzite and cubic phases for 40% and single cubic phase at Mg content greater than 50%. The variation of the cation-anion bond length to Mg content shows that the lattice constant of the hexagonal ZMO decreases with corresponding increase in Mg content, which result in the structure gradually deviating from the wurtzite structure. The optical measurements reveal a blue shift in absorption edge and increase in transmittance from 75% to 96% with increase in Mg content. Tuning of the band gap has been obtained from 3.41 to 6.58 eV with corresponding increase in Mg content from x = 0.0 to 1.0, which demonstrates that the films are useful for window layer of solar cells that improve the overall efficiency by decreasing the absorption loss. (C) 2008 Elsevier B.V. All rights reserved.