Nanocrystalline diamond (NCD) films are synthesized using microwave plasma enhanced chemical vapour deposition technique at 2 x 10(4) Pa and 600 degrees C with microwave power of 600-1600 W. Deposition is carried out on n-type (100) silicon wafer with Ar/H-2/CH4 gas mixtures. The film properties are analyzed using micro Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy and atomic force microscopy. Raman spectra show two predominant peaks centered around 1335 cm(-1) and 1560 cm(-1) and two humps around 1160 cm(-1) and 1450 cm(-1), respectively. FTIR spectra show C:H stretching modes around 3000 cm(-1). patterns show a peak at 44 degrees (2 theta). In situ diagnostic of plasma is carried out using Optical Emission Spectroscopy. It has been observed that C-2 dimer plays an important role in the nucleation of diamond crystals during NCD film deposition and the emission intensity of C-2 can be adjusted by varying the microwave power. It has also been observed that the structural properties like growth rate, surface morphology and grain size of the growing film are dependent on the C-2 intensity during deposition. (C) 2011 Elsevier B.V. All rights reserved.