Droplet Epitaxy Image Contrast in Mirror Electron Microscopy

Image simulation methods are applied to interpret mirror electron microscopy (MEM) images obtained from a movie of GaAs droplet epitaxy. The data for the surface profile and equipotential traces in Fig. 2 is contained in files Fig2height and Fig2EQ1-5, respectively. The format is (x, height) with units in microns. Figure 3 combines experimental data (top row) with four images simulated by ray tracing in an electric potential solved by finite element methods. The image intensity data is contained in file Fig3a in (red, green, blue) format and the simulated MEM image intensity data in Fig3b_A to D in the form (x, y, intensity). Atomic force microscope height data is shown in the top row of Fig. 4 and the corresponding data is contained in Fig4a-d (from left to right) in nm at equally spaced points or pixels on a 128 by 128 grid. The grid separation is 49.8 nm in x and y. Fig4e-h are line traces through the 3D data, in the format of (y, height) in nm. (e) corresponds to a line trace in y along the 92nd x pixel in (a), (f) corresponds to a line trace in y along the 56th x pixel in (b), (g) corresponds to a line trace in y along the 71st x pixel in (c), and (h) corresponds to a line trace in y along the 69th x pixel in (d). Fig5a-d contains surface height data in the format (x, height) in microns using interpolated functions included in file Fig5interpolate. Individually traced electron paths for Fig. 6a and Fig. 7a are contained in folders RawdataFig6 and RawdataFig7, respectively. Data is in the form (x, L - z) in m. The last line has the form (x, xVelocity/(-zVelocity) + x/(4*(L - delta))), where delta is the turning point distance, and xVelocity and zVelocity correspond to the velocities in those dimensions at the exit point. These two parameters were used in figures 6b and 7b to draw straight apparent rays near the virtual image plane, e.g. at a distance D the x coordinate on the plane is (x - D * (xVelocity/(-zVelocity) + x/(4*(L - delta))). 

Research results based upon these data are published at http://doi.org/10.1186/s11671-017-1837-y