Nitrogen (N)- and oxygen (O)-rich organic thin films were deposited by vacuum-ultraviolet (VUV)-assisted photo-chemical polymerisation of flowing ethylene (C2H4)-ammonia (NH3) and C2H4-nitrous oxide (N2O) mixtures of varying ratios, R, respectively. The reaction mechanism of these binary gas mixtures was investigated as a function of the wavelength, lambda, of two near-mono-chromatic VUV sources. Surface-near compositions of these "UV-PE:N" and "UV-PE:O" films were determined by X-ray photoelectron (XPS), and by Fourier transform (reflection-absorption) infrared (FTIR) spectroscopies. The two types of films were compared with plasma polymers deposited using low-pressure radiofrequency (r.f.) glow discharges in similar gas flow mixtures, "PPE:N" and 14 PPE:O". VUV-photochemistry appears to be superior to plasma-chemistry in its capability to produce nearly "mono-functional" organic thin films, ones that are rich in primary amines, -NH2, and in carboxylic acid groups, -COOH, respectively. (C) 2009 Elsevier Ltd. All rights reserved.