Thermal stability of carbon nitride thin films

The thermal stability of carbon nitride films, deposited by reactive direct current magnetron sputtering in N-2 discharge, was studied for postdeposit ion annealing temperatures T-A up to 1000 degreesC. Films were grown at tem peratures of 100 degreesC (amorphous structure) and 350 and 550 degreesC (f ullerenelike structure) and were analyzed with respect to thickness, compos ition, microstructure, bonding structure, and mechanical properties as a fu nction of T-A and annealing time. All properties investigated were found to be stable for annealing up to 300 degreesC for long times (> 48 h). For hi gher T-A, nitrogen is lost from the films and graphitization takes place. A t T-A = 500 degreesC the graphitization process takes up to 48 h while at T -A = 900 degreesC it takes less than 2 min. A comparison on the evolution o f x-ray photoelectron spectroscopy, electron energy loss spectroscopy and R aman spectra during annealing shows that for T-A > 800 degreesC, preferenti ally pyridinelike N and -C equivalent toN is lost from the films, mainly in the form of molecular N-2 and C2N2, while N substituted in graphite is pre served the longest in the structure. Films deposited at the higher temperat ure exhibit better thermal stability, but annealing at temperatures a few h undred degrees Celsius above the deposition temperature for long times is a lways detrimental for the mechanical properties of the films.