ISOTOPE FRACTIONATION IN THE SPUTTERING OF CU-63-CU-65

Under 2keV Xe ion bombardment of a (Cu69.1Cu30.9)-Cu-63-Cu-65 isotope mixture, isotope fractionation difference between small and large pola r emission angles, delta(15 degrees)-delta(75 degrees), was calculated by use of a dynamic Monte Carlo program. Calculation results show tha t delta(15 degrees) - delta(75 degrees) is large at both the zero flue nce and the high fluence, then it minimizes at a low fluence of 1.6x10 (15) ions/cm(2) between two fluence limits. An important cause of this minimum is that the surface composition gradient of Cu-63 maximizes a t the fluence of 1.6x10(15) ions/cm(2).