Single crystalline ceria samples with the composition Ce0.9Gd0.1O2-delta were pre-polarized with +/- 5 V for up to 300 s using a Pt coated AFM tip as working electrode. The direct contact zone had a diameter of <50 nm. Subsequently, the effect of the polarization on the surface potential of the samples was investigated by mapping the introduced defect gradient and its decay with time using Kelvin probe force microscopy. The generated surface potential gradients were found to have a diameter of up to 1 mu m, which is explained by the local ionization of defect associates by the applied high electric field. Measurements were performed at room temperature and 50 degrees C. The polarization behavior of the Ce0.9Gd0.1O2-delta single crystals was compared to cyclovoltammetry and polarization-relaxation experiments at T <= 350 degrees C and in dry air or nitrogen which were performed using a specially suited AFM (Controlled Atmosphere High Temperature Scanning Probe Microscope CAHT-SPM by Semilab). (C) 2016 The Electrochemical Society. All rights reserved.