Backscattering of Kilovolt Electrons from Solids

The total number and energy distribution of backscattered electrons at 0.2-4 kev incident energy ($V$) have been measured for six elements using electrostatic retarding potential techniques. For atomic number $Z\lesssim 30$, backscattering was found to be essentially independent of $V$ and almost linearly dependent on $Z$. For $Z\gtrsim 30$, backscattering decreases with decreasing $V$ below 2-3 kev to values less than those for elements of $Z\simeq 30$, and it no longer is a simple function of $Z$. The ratio of the mean energy of the backscattered electrons to that of the primaries is found to be close to one-half for $Z=6\mathrm{}$ and to increase only slightly for the heavier elements. These results are shown to indicate a dominant role of inelastic processes in the scattering of intermediate energy electrons, in contrast to scattering at very high energies, where elastic interactions control the phenomenon.