[en] During a surface treatment using CF₄/O₂ gas plasma, energetic ions affected the defect structures on the top surface of ITO thin films. C-AFM and local I-V measurements showed the formation of the depleted layer after a plasma treatment with a bias of 20 W; XPS showed the creation of new defect structures. Donor concentration in the damaged top surface of the ITO films was found to be decreased. Sn-based neutral defect complexes and reduced oxygen, which could trap the electrons, have been proposed to be formed. This can also explain the increase of the work function of ITO