Diamond-like carbon (DLC) films deposited on different substrates by plasma enhanced chemical vapour deposition were investigated. Bonding states and film quality were characterized by FT-IR spectroscopy. The influence of the power of plasma and the deposition time on the sp(2)/sp(3) ratio as well as the concentration of CHn bonds was studied. The influence of sp(2)/sp(3) ratio on the formation process of conducting channels in diamond-like carbon films as a result of electrical breakdown was determined. Reproducible increase of diamond-like carbon film conductivity, with initial sp(2)/sp(3) ratio larger than 0.16, was observed after electrical breakdown. (C) 2010 Elsevier B.V. All rights reserved.