Metallic and Semiconducting Nanowires from Single Wall Carbon Nanotubes
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Metallic and Semiconducting Nanowires from Single Wall Carbon Nanotubes Kousik Sivakumar, Shaoxin Lu and Balaji Panchapakesan* Delaware MEMS and Nanotechnology Laboratory Department of Electrical Engineering, University of Delaware, Newark, Delaware 19716, U.S.A. ABSTRACT The focus of today’s research has largely shifted from macro scale to micro scale and further to nano scale. The reason being the desire to realize quantum size effects in devices that has long eluded scientists around the world alike. With the discovery of nanoparticles, nanowires, and nanotubes, the ability to realize these effects practically into devices has increased manifold. Integration of carbon nanotubes with different types of functional materials may become mandatory in the future for electronics and sensing applications and in this sense, nucleation, growth and evolution of the structure of metallic and semiconducting materials on carbon nanotubes may be necessary. Further, it also provides opportunities to do fundamental research on understanding the structure-property relationships of these nanowires using carbon nanotubes. In this paper, we present a technique to form metallic and semiconducting nanowires using carbon nanotubes themselves as templates. Nanowires of silver and platinum have been fabricated by the electric field assisted deposition of nano particles of these metals on single walled carbon nanotubes. SEM and TEM investigations have shown the dimensions of the nanowires to be dependent only on the size of the nanoparticles, 10 – 100 nm in our case. The silver nanowires exhibited linear current – voltage characteristics whereas the platinum nanowires exhibited non-linear characteristics beyond a certain bias. This technique provides a high degree of selectivity by manipulating the charges on the surface of the nanotubes, which enables the deposition of metals only on the nanotubes and not anywhere else. The versatility of this technique allows for the fabrication of different types of metallic and semiconducting nanowires at the same dimensions as carbon nanotubes. INTRODUCTION Carbon nanotubes (CNTs) have grown to be interesting materials in recent years ever since it was discovered by Iijima [1], due to their unique electronic [2-5] and extraordinary mechanical properties [6-9]. Their thermal conductivity is higher than diamond and their mechanical properties such as stiffness, strength and resilience exceeds any current material [6]. CNTs can be metallic or semiconducting depending on the tube diameter and chirality that thus offers possibilities to create semiconductor-semiconductor and semiconductor-metal junctions useful in electronic and sensor devices. An excellent review of structure and properties of CNTs can be found elsewhere in references [10-12]. Integration of different types of material systems on nanotube surfaces can lead to the development of hybrid material systems that are often required in making electronic and sensor devices. Metallic and metal oxide nanowires can provide catalytic propert
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