In this work, a conductive atomic force microscope (C-AFM), a scanning capacitance microscope (SCM), and a kelvin probe force microscope (KPFM) have been used to qualitatively study at the nanoscale the electrical properties of irradiated and implanted gate oxides of metal-oxide-semiconductor structures. These techniques have allowed to investigate the electrical conduction (C-AFM) and the presence of charge (SCM and KPFM) in the oxide of the analyzed structures. The impact of the energy of the impinging ions has also been qualitatively evaluated. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3043475]