Anomaly in Sputtering of Aluminum under $\bf N_{2}^{+}$ Ion Bombardment

Sputtering yield measurement of Al for N-2(+) ion bombardment with different primary energies has revealed that the sputtering yield at a primary energy of 500 eV is nearly zero, whilst the yields for primary energies greater than 1 keV appear to be similar to those for inert gas ion sputtering which has been described well theoretically and by computer simulations. The sputtering yields are negative for primary energies below several hundred eV at the initial stage of sputtering, which indicates that incident ions are trapped in the specimen and collision cascade results in very little sputtering. Computer simulations for these sputtering processes have also been carried out in order to understand the mechanism of sputtering with reactive ions.