Linking Catalyst Phase with CNT Morphology and its Subsequent Field Emission Characteristics: An Optimization Study

Abstract

The effect of phase transition in catalyst nanoparticles due to increasing growth temperatures and its effect over the morphology and field emission of carbon nanotubes (CNT) films is reported here. Thin Fe film coated Si substrates are used to obtain Fe nanoparticles under hydrogen and argon plasma treatment. For this, three different microwave powers (400, 500 and 650 watts) in a microwave plasma enhanced CVD system is used. TEM images of plasma annealed films shows Fe nanoparticles of size ranging from 10 nm to 70 nm. The SAED images of these Fe nanoparticles shows additional diffraction rings for the films annealed at higher microwave power (i.e., higher growth temperatures). Acetylene and hydrogen plasma is used for 2 minutes to deposit the CNT films over three different sized Fe nanoparticles. High resolution TEM (HRTEM) images are used to further investigate any effect of growth temperature on catalyst encapsulated in the CNTs. The field emission studies and Kelvin probe measurements are carried out to examine the suitability of films for its field emission application. It is established that, only under specific optimized growth parameters CNT film must be grown for its usefulness as efficient field emitters.