The field emission properties of a variety of nitrogen-containing hydrogenated amorphous carbon films have been characterised as a function of film thickness and substrate type. Identified trends have been discussed in terms of the optical band-gap and refractive index of the films, and the surface roughness of the substrates. In addition, carbon-based materials have been considered as inexpensive film-compatible substrates, and an in-situ oxygen plasma pre-treatment has been investigated as a means of changing the field enhancement factor of the system. We have achieved field emission with threshold voltages as low as 8 V μm−1, and we present data that supports the view that the electron emission from amorphous carbon is dependent on the nature of the back contact, and possibly the ease at which the film can be fully depleted, i.e. film thickness.