Extended Data Fig. 3: Quantification of spatial resolution.

a, Surface charge density reconstruction (Fig. 2g of the main text) with highlighted region (dashed lines) and step edge (arrows) used for analysis in panels b and c. Scale bar, 1 μm. b, Example of the 10% - 90% rise distance extraction method used to estimate the spatial resolution. The blue (red) shaded area denotes the range of data points used to define the lower (upper) value of the step edge. The dashed black lines denote the rise interval for the data trace (purple). The highlighted red datapoints were used in a linear fit (gray line), which was then used to extract a rise distance of 75 nm. c, Histogram binning of rise distances across the region denoted in panel a and Gaussian fit which yields a mean value of 95 nm.