Noncontact AFM image showing topographic ripples on the layer close to the edge of the sample. On P1 and P2 curves were recorded for Fig. 2.
Typical curves taken at P1 and P2 of Fig. 1. and indicate the corresponding flatband positions. and depend on the oxide thickness at P1 and P2.
(a) Cross section of an arbitrary ripple. The average oxide thickness was measured by ellipsometry and added to the thickness variations determined by AFM. (b) Measured oxide capacitance on different spots along a line separated by 250 nm. (c) Flatband voltages on the same positions.
The reciprocal of the oxide capacitance is plotted vs the thickness of the oxide on a ripple. The dashed line shows a linear fit to the data, the gray area covers everything within one standard deviation. The inset zooms into the data for better clarity.
Local oxide charge density on a line of our sample. The (negative) charge density is largest on the ridge and smallest on the trough of a ripple.
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