EFFECT ON ELECTRON-ENERGY ON AMORPHIZATION OF ZRCR2

The influence of electron energy on the amorphization of ZrCr2 at 25 K was measured. Amorphization was observed at electron energies from 90 0 to 330 keV. The dose-to-amorphization increases with decreasing elec tron energy with two steps, one at 700 keV corresponding to the decrea se in the Zr displacement cross section due to the approaching displac ement threshold of Zr and one at 500 keV corresponding to an appreciab le decrease in the displacement cross section of Cr due to the approac hing displacement threshold for Cr. At lower electron energies, it is believed that amorphization occurs principally through a secondary dis placement mechanism, where light impurity atoms (mainly O) are displac ed by electrons and displace in turn the heavier atoms. By fitting the results using electron displacement cross sections, we find the displ acement energies in each sublattice to be E(d)(Zr) = 22 eV, E(d)(Cr) = 23 eV, E(d)(O) = 4 eV. (C) 1996 American Institute of Physics.