Electrical properties of carbon nitride thin films: Role of morphology and hydrogen content

The influence of hydrogen content and ambient humidity on the electrical properties of carbon nitride (CNX) films deposited by reactive magnetron sputtering from a graphite target in Ar discharges mixed with N-2 and H-2 at a substrate temperature of 350degreesC have been investigated. Carbon films deposited in pure Ar exhibit a dark resistivity at room temperature of similar to4 X 10(-2) Omegacm, while the resistivity is one order of magnitude lower for CN0.25 films deposited in pure N-2, due to their denser morphology. The increasing H-2 fraction in the discharge gas leads to an increased resistivity for all gas mixtures. This is most pronounced for the nitrogen-free films deposited in an Ar/H-2 mixture, where the resistivity increases by over four orders of magnitude. This can be related to a decreased electron mobility as H inhibits the formation of double bonds. After exposure to air, the resistivity increases with time through two different diffusion regimes. The measured electrical properties of the films are related to the apparent film microstructure, bonding nature, and ambient humidity.