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

Preliminary investigations suggest that a crystalline carbon nitride compound corresponding to the new beta-C3N4 phase can be synthesized by a dual ion beam sputtering deposition technique. Two Kaufman ion sources 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 eV nitrogen ions beam at a temperature of 400 degrees C. Rutherford backscattering (RBS) analysis shows that the nitrogen content is very close to the value expected for the beta-C3N4 compound. The density of the films measured by X-ray reflectometry is found to be about 3.4 compared 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 crystallized grains of 50-100 nm although the presence of a second amorphous phase is also observed. The electron diffraction patterns are in good agreement with those predicted theoretically for the new beta-C3N4 phase.