The injected-charge contrast mechanism in scanned imaging of doped semiconductors by very slow electrons

Scanning Electron Microscopy with Samples in an Electric Field

“…Finally, we consider an alternative contrast mechanism that appears on p-type patterns illuminated with electrons in the range of units of eV [50]. Experiments were made with the cathode lens configuration according to Figure 5 and provided micrographs with extremely high contrasts appearing even inside the p-type patterns (Figure 20).…”

“…Low reproducibility of the quantitative data was obviously due to measuring each dopant concentration on a separate sample of a not exactly defined surface status. So as to avoid differences in the history of samples, a dedicated sample was manufactured with the dopant density varying within a broad range of four orders of magnitude along groups of strips and rectangles (see Figure 20) [50]. The samples were available in both n/p and p/n combinations.…”

Very low energy scanning electron microscopy

“…The effect should be observable on grains in polycrystals (see Fig. 8) and on doped patterns in semiconductors [13].…”

“…When using an incident beam of energy near to this bias, we get from the sample a BSE flux of a still quite broad energy and angular distributions but from the biased area we may acquire a narrow, totally reflected quasimonochromatic pencil. As in observations of the lateral fields, what is crucial is which part from all emitted fluxes is captured by the detector [13]. The mirror electron microscopy (MEM) mode [14,15], which is closely related to our topic, is not treated here but any user of the SLEEM instrument would profit from familiarity with the basics of the MEM.…”

Dopant Contrast in Semiconductors as Interpretation Challenge at Imaging by Electrons

“…Explanation of the phenomena observed is based on a non-equilibrium state connected with dynamic recombination of holes in the p-type by a large flux of incident electrons, leaving the ionized acceptors charge unbalanced. 20) This injected-charge contrast naturally depends on the incident electron dose and there are chances for measuring the dopant density via this dependence. Similar possibility has not been excluded for the contrast of the local density of states, available at low beam currents.…”