The stability of nitrogen-containing amorphous carbon films after annealing at moderate temperatures

The future of electronic devices fabricated from amorphous carbon films will only be ensured if the optical, electrical, and structural properties of the material remain stable in a variety of operating conditions, including moderate short-term elevations in temperature. In addition, the sensitivity of these metastable films to structural changes as a consequence of their thermal history provides a good opportunity to further modify and tune the material by using carefully applied heat treatments. This paper begins to address both these concerns by studying the variation of the optical band-gap and refractive index of a variety of amorphous carbon films deposited using plasma-enhanced chemical vapour deposition techniques. It shows that the expected graphitisation of the carbon films occurs after relatively short annealing times even at moderate temperatures, but that there is scope to improve the quality of the films prior to the onset of degradation. (C) 1998 Elsevier Science S.A.