FORMATION OF THE CRYSTALLINE BETA-C3N4 PHASE BY DUAL-ION BEAM SPUTTERING DEPOSITION

Preliminary investigations suggest that a crystalline carbon nitride c ompound corresponding to the new beta-C3N4 phase can be synthesized by a dual ion beam sputtering deposition technique. Two Kaufman ion sour ces have been used, one for sputtering a graphite target with 1.2 keV Ar+ ions and a second one for bombarding the growing film with a 600 e V nitrogen ions beam at a temperature of 400 degrees C. Rutherford bac kscattering (RBS) analysis shows that the nitrogen content is very clo se to the value expected for the beta-C3N4 compound. The density of th e films measured by X-ray reflectometry is found to be about 3.4 compa red with a theoretical value of 3.47. The microstructural state of the films has been investigated by transmission electron microscopy (TEM) and our results indicate that the films are mainly formed of small cr ystallized grains of 50-100 nm although the presence of a second amorp hous phase is also observed. The electron diffraction patterns are in good agreement with those predicted theoretically for the new beta-C3N 4 phase.