Gas evolution studies for structural characterization of hydrogenated carbon nitride samples

Gas evolution experiments have been performed on hydrogenated carbon nitride samples in order to study the thermal stability of such samples and to investigate the presence of molecular nitrogen within the samples. The films were deposited by a combination of nitrogen and acetylene as precursor gases using an electron cyclotron wave resonance source. The results show for the release of molecular hydrogen broad effusion transients extending from approximately 300 to 900 T. In addition to H, and hydrocarbons CxHy usually observed for hydrogenated carbon films, there is a significant release of HCN molecules. This effusion also sets in at temperatures near 300 degreesC and shows a broad maximum near 700 degreesC. Above approximately 500 degreesC, for most of the samples the evolution of nitrogen rises steadily with increasing temperature, i.e. the effusion maximum is at temperatures exceeding the temperature range (100-1050 degreesC) investigated. However, in the nitrogen content range from 15 at.% to approximately 25 at.%, a peak near 300 degreesC is also observed. It becomes less pronounced at higher nitrogen content. This peak is probably a consequence of molecular nitrogen that is included in the sample without bonding, in (isolated) voids or bubbles. The implications for film properties, composition and thermal stability are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.