Quantitative analysis of chemically-enhanced sputtering during ion beam deposition of carbon nitride thin films

The sputter losses during growth of carbon nitride thin films using mass selected ion beam deposition of C{sup +} and N{sup +} ions with energies between 20 eV and 500 eV are studied. Depending on the ion energy 35--100% of C{sup +} but only 3--35% of N{sup +} ions are incorporated in the films. Thus the films are always strongly nitrogen-deficient. To suppress the preferential loss of nitrogen the authors introduce the concept of continuously growing surface protective layers. Starting from a diamond-like carbon film as substrate, carbon nitride films are deposited using 100 eV {sup 12}C{sup +} and 1 keV {sup 14}N{sup +} ions, so that the growing films are always covered with a 1--2 nm thick protective layer of amorphous carbon. In this case they observe an increased nitrogen incorporation yielding to films with average film composition of C{sub 2}N.