Carbon nanotubes (CNTs) were grown on Ni/TiN/Si and Ni/TiN/glass substrates by microwave plasma enhanced chemical vapor deposition using methane and hydrogen gases. Firstly, TiN buffer (200 nm) and Ni catalyst (60 nm) layers were deposited on the glass and Si wafers by radio frequency magnetron sputtering method. The substrate DC bias voltage as the main process parameter was changed from 0 to -250 V in -50 V intervals and the synthesis temperature was maintained at the condition of 600 degrees C. The effects of DC bias voltage on structural and electrical properties of the synthesized CNTs were investigated. The length of CNTs is changed by supplying substrate DC bias voltage. It is observed that negative bias is more Profitable for obtaining the vertically aligned CNTs than that without bias. As the multi-walled CNTs, the increase of DC bias voltage decreases the I-D/I-G ratio and the disorder of CNTs, and also it is attributed to the improvement of the crystal quality of CNTs and the reduction of conductivity of CNTs. (c) 2013 Published by Elsevier B.V.