Structural And Optical Properties Of Sol-gel Processed ZnCdMgO Nanostructured Films As Transparent Conductor
Praveen Kumar, Amritpal Singh, Dinesh Pathak, Ludek Hromadko and Tomas Wagner
Keywords: Thin films; transparent conducting oxides; wide band gap semiconductors; transparency; conductivity.
In the present work, we report the structural and optical properties of sol-gel synthesized Zn0.9(Cd1-xMgx)0.1O (0 ≤ x ≤ 1.0) nanostructured films investigated by using the X-ray diffraction, scanning electron microscopy, atomic force microscopy, electrical resistivity, optical absorption and photoluminescence spectroscopic techniques. The X-ray diffraction study has revealed the hexagonal wurtzite crystal structure having favorable c-axis orientation for the increase in Mg concentration. The stress-strain calculation reveals the compressive stresses in Cd rich films whereas Mg rich films experience the tensile stress. Reduction of grain size and surface roughness has been observed with the increase in Mg concentration with more spherical grains. The AFM and SEM micrographs reveal the smooth surface morphology of the synthesized films. The magnesium rich films show high transmission in the visible and NIR region but show decrease in it with the increase in Cd concentration. The band gap increases from 3.19 to 3.40 eV with increase in Mg content. The photoluminescence measurement reveals the decrease in the defects and increase in band gap with the increase in Mg content in the films. The electrical resistivity has been found to be increased from 0.3×102 to 169.4×102 Ω-cm with increase in Mg concentration. The present study reports that the compositions x=0.4 and x=0.6 have the optimized combination of optical transmittance and better electrical resistivity values in this system for their possible applications as transparent conductors. The present results provide important data for TCOs processing with an optimized content of metal dopants for better transparency and conductivity.