We studied electrical effects observed on irradiated surfaces Of SiO2/Si at macroscopic and nanoscopic scales. Irradiation is performed using high energy and low-density ion beams. Macroscopic measurements are obtained using vibrating capacitor with probe diameter of 1 mm. Nanoscopic properties (both morphology and electrical effects) are measured using electrostatic force and nanoKelvin microscopy working in vacuum. We show mappings of electrical effects and discuss about the criteria allowing to separate potential effects from trapped electrical charge effects. (C) 2003 Elsevier Science B.V. All rights reserved.