Optical and electronic properties of plasma-deposited hydrogenated amorphous carbon nitride and carbon oxide films

• Published in: Thin solid films 2005-06, Vol.482 (1), p.24-33
• Main Authors: Godet, C., Adamopoulos, G., Kumar, Sushil, Katsuno, T.
• Format: Article
• Language: English
• Subjects: Carbon oxide films; Plasma-deposited hydrogenated amorphous carbon nitride; Raman studies
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2004.11.112

A comparative investigation of the nanostructural vs. electronic properties of DECR plasma deposited carbon nitride and carbon oxide alloys provides new insights in the changes of the sp 2-clusters and sp 3 matrix resulting from the decrease in the average coordination number, as N and O atoms are increasingly incorporated. This review emphasizes the similar incorporation efficiency of N and O atoms in the carbon matrix as a function of the gas phase mixture (C 2H 2, N 2) or (C 2H 2, O 2), the decrease in the alloy density deduced from Nuclear Reaction Analysis and optical measurements, and the better ordering of the sp 2-hybridized carbon phase evidenced by Raman studies. Opposite variations in the ohmic conductivity σ( T), apparent activation energy E ACT and hopping transport parameters (related to the localization parameter N( E F) γ −3) are found as a function of the (N/N+C) and (O/O+C) stoichiometries. This surprising result gives evidence of some competition between the improved ordering of the sp 2 phase shown by Raman spectra in both alloys (stronger in a-C 1− x N x :H with a large influence of aromatic clusters) and the increasing polymer-like character of the sp 3 matrix, dominant in a-C 1− x O x :H films where the weaker connectivity of the sp 3 matrix is attributed to two-fold bonded oxygen atoms C–O–C and terminating C O groups. The role of π  and π* states localization is discussed in the context of bandtail hopping conductivity.