Room temperature diluted magnetism in Li, Na and K co-doped ZnO synthesized by solution combustion method

Abstract

In this effort the alkali dopants Li, Na and K are co-doped with ZnO by solution combustion technique. This work is the production of room temperature ferromagnetism along with a rare orange emission from ZnO with equally concentrated Li, Na and K impurities. The XRD analysis reveals the hexagonal wurtzite structure and the substitution of the alkali in ZnO. The SEM and EDAX study shows the morphology and impurity free samples of ZnAO. The interstitial Zn atoms and the strain produced in the crystal structure due to alkali dopants is reflected in the FT Raman spectra. The band gap determined from the UV-Vis-NIR shows a variation that follows the variation of the grain size. The PL emission spectra brings to limelight the abundance of interstitial O atoms that involves in orange emission. The oxygen vacancies in the sample produce a weak green emission that decreases and then increases with alkali content. There is also a weak UV emission due to bound acceptor–donor recombination. The magnetometry establishes the fact that the direct bandgap semiconductor ZnO becomes magnetically sensitive due to the presence of alkali thereby making ZnO:Li+Na+K as a member of the family of dilute magnetic semiconductors. To the best of our knowledge this is the first report on the ferromagnetism observed in Li, Na and K co-doped ZnO.