Influence of disorder on localization and density of states in amorphous carbon nitride thin films systems rich in π-bonded carbon atoms

摘要

We discuss in this paper the evolution of both the density of states (DOS) located between the band-tail states and the DOS around the Fermi level N(E_F) in amorphous carbon nitride films (a-CN_x) as a function of the total nitrogen partial pressure ratio in the Ar/N_2 plasma mixture. The films were deposited by three different deposition techniques and their microstructure was characterized using a combination of infrared and Raman spectroscopy and optical transmission experiments, completed with electrical conductivity measurements, as a function of temperature. The observed changes in the optoelectronic properties are attributed to the modification in the atomic bonding structures, which were induced by N incorporation, accompanied by an increase in the sp~2 carbon bonding configurations and their relative disorder. The electrical conductivity variation was interpreted in terms of local effects on the nature and energy distribution of π and π~* states.