Due to the nanoscale structures of carbon nanotubes with highly appreciable optical, thermal and electrical properties which has lead it into a challenging purpose for many potential applications in the nano channel FET, MOSFET, MISC, biosensors, magnetic storage, memory devices etc. The preparation techniques of CNTs by conventional CVD or ARC plasma Discharge method is substituted by the low cost and easy pyrolysis technique as referred in a paper is used for the preparation of CNTs and the prepared CNT is characterized by XRD, SEM . Then a device using the millimetre long CNT, synthesized by CVD technique, as channel is fabricated in a simple manner and the substrate induced biasing effect has studied by the current -voltage characterization by using the source meter, showing the metallic behaviour of multi walled CNT channel. The change in resistance due to the exposure of fabricated device towards different external factors like LASER beam and the water vapour is observed, which shows the change in surface activity due to the influence of foreign molecules
