The Zn0.9Co0.1O films are fabricated by chemical solution deposition method. All the films have the ZnO wurtzite structure with a preferential orientation along the c-axis. The analysis of X-ray near-edge absorption spectroscopy and X-ray photoelectron spectroscopy indicates that the valence of Co is +2, and there are oxygen vacancies in Zn0.9Co0.1O films annealed in Ar atmosphere. Extended X-ray absorption fine structure results reveal that Co2+ ions have dissolved into ZnO and substituted for Zn2+ ions. Magnetization measurements show that the film annealed in Ar exhibits ferromagnetism which can be explained by the formation of bound magnetic polarons. (C) 2011 Elsevier B. V. All rights reserved.