Amorphous fluorinated carbon films were grown from CF4 and C2H2 mixtures, using a Plasma Assisted Chemical Vapour Deposition (PACVD) apparatus. Two sets of films were deposited, changing in a systematic way the CF4 flux and the bias voltage (V-b). Film composition and structure were analysed by secondary ion mass spectroscopy (SIMS), infrared (IR) and Raman spectroscopies. Film hardness was obtained by micro-indentation measurements. On increasing fluorine content in films, hardness decreases and a fluorescence background in Raman spectra appears at high fluorine content, showing a diamond- to polymer-like structural transition. Infrared spectra indicate the presence of -CFx, C=CHF and C=CF2 groups in the films. Our data are compared with previous results in the literature and the mechanisms involved in film formation are discussed, especially regarding fluorine substitution for hydrogen. (C) 2002 Elsevier Science B.V. All rights reserved.