Boron doped diamond nanocrystals were grown on Si wafers through introduction of the gas mixture of B2O3 dissolved in ethanol and hydrogen by a hot filament chemical vapor deposition (HFCVD) technique. Boron level in diamond films were controlled in the range from 100 to 500 ppm by adjusting the B/C ratios of gas mixtures in order to synthesize and improve the conductivity and quality of HFCVD diamond films with cluster size of nanometer To investigate the effect of different boron percentage in the chamber on deposited films, Raman spectroscopy, field emission scanning electron microscopy and four point probe techniques were applied to characterize the properties of diamond films. Experimental results indicated that higher boron incorporation in the diamond films introduced bigger crystal clusters, better crystal quality and smaller film resistivity when the level of boron increased from 100 to 300 ppm, while they showed an opposite trend with a further increase of boron level from 300 to 500 ppm. However, in any case the higher boron-doping level led to a decrease of the non-diamond phase in the nanodiamond films. (C) 2015 Elsevier B.V. All rights reserved.