The un-doped and Mn doped ZnO thin films, with oxygen rich stoichiometry, were deposited onto Si (1 0 0) substrate using spin coating technique. The structural analysis revealed the hexagonal wurtzite structure without any impurity phase formation. A consistent increase in cell volume with the increase in Mn doping concentration confirmed the successful incorporation of bigger sized tetrahedral Mn2+ ions (0.83 angstrom) in ZnO host matrix that was also endorsed by the presence of Mn 2p(3/2) core level XPS spectroscopic peak. Extended deep level emission (DLE) spectra centered at similar to 627 nm confirmed the presence of oxygen interstitials. Moreover, the magnetic measurements of field dependent M-H curves revealed the origin of ferromagnetic ordering from Mn-defect pair exchange coupling with oxygen interstitials in ZnO host matrix. (C) 2012 Elsevier B.V. All rights reserved.