Fig. 1: Formation of the charge pattern.
From: Electret formation in transition metal oxides by electrochemical amorphization
a Surface topographic image of the pristine film. The white boxed area indicates the region scanned by a positively biased tip. b Topographic image after the electroforming process. c Relative EFM phase map measured under VEFM = +4 V. d Relative surface potential map in the same region. e Height profiles before (blue) and after (red) the electroforming process. f Relative EFM phase profiles and g average relative phase values in the electroformed regions for various VEFM values. The light red line is a guideline for the eye. h Profile data of the relative surface potential. All scale bars represent 2 μm, and all profile data were obtained from the corresponding red dotted lines in a–d.
