Magnetism as a tool for band-gap narrowing of zinc oxide films prepared by sol–gel method

Abstract: sp–d exchange interaction was used to narrow the room-temperature band gap of zinc oxide films prepared by sol–gel method. Zinc oxide was doped with manganese ions by adding manganese chloride to the precursor and post-annealing in hydrogen. Films with different concentrations of manganese were prepared. Exchange interaction was established between the manganese ions in the lattice by introducing oxygen vacancies. The magnetic moment was found to increase with the concentration of manganese. For low concentrations of manganese, the band gap of the doped semiconductor was found to be wider than that of undoped ZnO films, in agreement with Vegard’s law. High concentrations of dopant resulted in a narrowing of the band gap. We ascribe the narrowing of the band gap to conduction band-edge Zeeman shifting. Graphical Abstract: 12 at.% Mn was successfully substituted in ZnO films deposited by sol–gel method. Exchange interaction was established between the Mn ions through the mediation of oxygen vacancies. A narrowing of the band gap of ZnO was achieved by Zeeman shifting of the bottom of the conduction band.[Figure not available: see fulltext.]