Examples of GEIS results for low doping current intensities. Evolution in time of Nyquist plots during the Er doping of two nominally identical PSi samples, 1.25 μm thick, carried out at low current intensities (I = +0.010 mA for a and I = +0.015 mA for b). For each section in the figure, the first measurement is the lowest curve. All GEIS cycles have been measured in sequence with an interval of about 4 s between a cycle and the next. Curves related to increasing times are shifted in the y-axis for reason of clarity, and an arrow indicating the direction of time is indicated.