Growth of Carbon Nanotubes on Copper Substrates Using a Nickel Thin Film Catalyst
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Growth of Carbon Nanotubes on Copper Substrates Using a Nickel Thin Film Catalyst Gowtam Atthipalli1, Prashant N. Kumta1,2,3, Wei Wang1, Rigved Epur1, Prashanth H. Jampani2, Brett L. Allen4 , Yifan Tang4, Alexander Star4, Jennifer L. Gray1 1
Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261, U.S.A. 2 Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261, U.S.A. 3 Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261, U.S.A. 4 Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15261, U.S.A.
ABSTRACT Carbon nanotubes with their attractive properties, one-dimensional geometry, and their large aspect ratio are ideal candidates for a variety of applications including energy storage, sensing, nanoelectronics, among others. We have studied the growth of carbon nanotubes on copper substrates using a nickel thin film as a catalyst. The catalyst was sputtered in a chamber with a base pressure in the ultra-high-vacuum regime. By adjusting the sputtering parameters, the effects of the morphology and the thickness of the nickel catalyst on the growth of carbon nanotubes have also been investigated. Multiple hydrocarbon sources as carbon feedstock (methane, acetylene and m-xylene), corresponding catalyst precursors and varying temperature conditions were used during chemical vapor deposition (CVD) process to understand and determine the best conditions for growth of carbon nanotubes on copper. Correlation between the thickness of the thin film nickel catalyst and the carbon nanotube diameter is also presented in the study. Characterization techniques used to study the morphology of the CNTs grown on copper include SEM, TEM, HRTEM, Raman Spectroscopy. Results of these studies are outlined and discussed. INTRODUCTION Since the discovery of carbon nanotubes there has been enormous interest to synthesize directed nanotube growth [1]. The reason for this interest in nanotubes is due to their excellent physical properties such as high mechanical strength, high aspect ratio and good thermal conductivity [2,3]. There have been extensive publications in recent years to demonstrate the growth of both random and aligned nanotubes [4-7]. However for device applications where the nanotubes serve as electrical conductors, directed carbon nanotube growth is preferred. Typically, the nanotubes are grown using a method such as chemical vapor deposition (CVD) on metal catalyst particles or islands that are deposited on top of a semiconducting or insulating substrate. However, for many envisioned applications, it would be beneficial for the nanotubes to be directly grown on a common conducting substrate such as copper to ensure good electrical contact. The primary objective of this study is to grow vertically aligned carbon nanotubes (VACNTs) on copper substrates using the chemical vapor deposition method. Such structures could also be used as a conductive support or scaffold structure for fabricat
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