The characteristics of carbon nanotubes grown at low temperature for electronic device application

For the application of carbon nanotubes (CNTs) in flexible electronic devices, the CNTs were grown on Corning 1737 glass substrate by microwave plasma enhanced chemical vapor deposition (MPECVD) method. To deposit the catalyst layer, TiN buffer layer of 200 nm thickness and Ni catalyst layer of 60 nm were first deposited on the glass by r.f. magnetron sputtering method. The CH ₄ and H₂ gases are used as the synthesis gas of CNTs and the working pressure was about 2.13 kPa, and the substrate bias was about -200 V. The growth time was from 2 min to 5 min and the microwave power was about 800 W. The substrate temperature as the main parameter was changed from 400 °C to 550 °C. The structural properties of CNTs synthesized with the substrate temperature were investigated using Raman, field emission scanning electron microscopy, and transmission electron microscopy methods. The surface and electrical properties of CNTs grown by MPECVD method were studied by scanning probe microscopy and four-point probe methods. We obtained the multi-walled CNTs (MW-CNTs). Multi-walled CNTs were vertically grown on Ni/TiN/glass substrates below 500 °C without any glass deformations. As the substrate temperature was increased, the crystallinity of CNTs was improved. Ni catalyst was found at the tip of CNT by the TEM observation and the grown CNTs were found to have a multi-walled with bamboo like structure.