Band-gap variation in Mg- and Cd-doped ZnO nanostructures and molecular clusters

Abstract

We study the effect of doping on band gap in Mg- and Cd-doped zinc oxide nanostructures and molecular clusters. The fabrication of doped nanostructures was carried out via solution route. The lower doping efficiency of Cd than that of Mg has been explained in terms of binding energy. The band gap varied from $3.04\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ in Cd-doped ($9.1\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$ of Cd) nanostructure to $3.99\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ in Mg-doped ($16.8\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$ of Mg) nanostructure. Theoretical analysis using first-principles molecular dynamics techniques on pristine and doped ZnO clusters shows that the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital exhibits a similar variation as does the band gap in nanostructures with the varying concentration of Mg and Cd.