Hydrogenated amorphous carbon (a-C:H) films were deposited in a plasma-enhanced chemical vapour deposition system and the effects of altering the electrical properties of the films on the field emission properties has been examined as a function of nitrogen content and substrate resistivity. Experimental results show a lowering of the threshold electric field with nitrogen content, from about 25 V mum(-1) (for 0 at.%) to approximately 12 V mum(-1) (for 7 at.% nitrogen). The properties of wide gap polymeric films (PAC) deposited on the earthed electrode are compared with the more diamond-like films (DAC) deposited on the powered electrode. Films that are diamond-like in nature show threshold fields that are on an average 10 V mum(-1) lower than the polymeric films. This paper also reports on the development of a computer simulation space charge induced band bending electron emission model for the a-C:H. The computer simulations also reflect the variation observed in the threshold fields experimentally and give us confidence as to the proposed emission mechanism based on space charge induced band bending giving rise to electron emission.