Diamond like carbon (DLC) coatings were deposited on silicon(1 1 1) substrates by microwave electron cyclotron resonance (ECR) plasma CVD process using a plasma of Ar and CH4 gases under the influence of DC self bias generated on the substrates by application of RF (13.56 MHz) power. DLC coatings were deposited under the varying influence of DC bias ( - 60 V to - 150 V) on the Si substrates. Deposited films were analyzed by different techniques like: X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), atomic force microscopy (AFM), Hardness and elastic modulus determination technique, Raman spectroscopy, scanning electron microscopy (SEM) and contact angle measurement. The results indicate that the film grown at - 100 V bias has optimised properties like high sp(3)/sp(2) ratio of carbon bonding, high refractive index (2.26 - 2.17) over wide spectral range 400 - 1200 nm, low roughness of 0.8 nm, high contact angle (80 degrees) compared to the films deposited at other bias voltages ( - 60 V and - 150 V). The results are consistent with each other and find august explanation under the subplantation model for DLC growth. (c) 2007 Elsevier B.V. All rights reserved.