Vertically Aligned Carbon Nanotubes Growth Using Self-assembled Ni Nanoparticles Produced by Ion Implantation

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0960-N08-01

Vertically Aligned Carbon Nanotubes Growth Using Self-assembled Ni Nanoparticles Produced by Ion Implantation D. L. Baptista1, J. M. J. Lopes1, M. J. Morschbacher1, S. H. Dalal2, S. P. Oei2, K. B. K. Teo2, W. I. Milne2, and F. C. Zawislak1 1 Instituto de Física, UFRGS, Porto Alegre, 91501-970, Brazil 2 Engineering Department, University of Cambridge, Cambridge, CB3 0FA, United Kingdom

ABSTRACT An alternative method for seeding catalyst nanoparticles for carbon nanotubes and nanowires growth is presented. Ni nanoparticles are formed inside a 450 nm SiO2 film on (100) Si wafers through the implantation of Ni ions at fluences of 7.5x1015 and 1.7x1016 ions.cm-2 and post-annealing treatments at 700, 900 and 1100 °C. After exposed to the surface by HF dip etching, the Ni nanoparticles are used as catalyst for the growth of vertically aligned carbon nanotubes by direct current plasma enhanced chemical vapor deposition. INTRODUCTION The catalytic growth of vertically aligned carbon nanotubes (CNTs) by plasma enhanced chemical vapor deposition (PECVD) and semiconductor nanowires by chemical vapor deposition (CVD) or vapor-liquid-solid (VLS) mechanism opened up the possibility of exploiting these 1-D nanostructures in reliable bottom-up devices fabrication [1,2]. Carbon nanotube arrays grown by PECVD have been quoted for applications in sensing and field emission since they are vertically aligned. It is also desirable to incorporate vertically carbon nanotubes arrays into micro/nanoelectromechanical systems (M/NEMS) [3]. Using standard lithography, one can define the catalyst positions on the substrate and therefore promoting a localized and selective CNT growth. However, limitations are encountered when large area pattering or placing catalyst particles on the bottom of high aspect ratio structures is required. As an alternative method, the use of catalyst metal particles produced by ion implantation and post-annealing treatment has attracted interest [4]. The main idea is to produce embedded catalyst metal nanoparticles into etchable layers such as SiO2. By performing selective etching, it is possible to expose directly the catalyst where it is desirable. In this work we report the formation of self-assembled Ni nanoparticles by ion implantation and its application as catalytic seeds for the growth of vertically aligned carbon nanotube arrays. EXPERIMENT Ni nanoparticles were formed inside a 450 nm SiO2 layer on (100) Si substrates through the implantation of Ni ions using a 500 kV HVEE ion implanter. The implantation was performed at two energies of 100 and 170 keV and fluences of 7.5x1015 and 1.7x1016 Ni.cm-2

respectively, resulting in the formation of a Ni plateau with concentration of 3.5 at.%. Postannealing treatments at 700, 900 and 1100 °C in N2 atmosphere for 30 min. were conducted to form Ni nanoparticles with different densities and diameters. Diluted HF solution was used to etch part of the SiO2 layer until exposing the nanoparticles to the surface. Finally, vertically aligned carbon nanotubes arr

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