%0 Journal Article
%T Modulation of Carbon Nanotube Metal Contacts in Gaseous Hydrogen Environment
%A A. R. Usgaocar
%A Harold M. H. Chong
%A C. H. de Groot
%J Journal of Nanoscience
%D 2014
%R 10.1155/2014/404519
%X Carbon nanotubes (CNTs), contacted by electrodeposited Pd0.59Ni0.41 alloys, are characterised using electrical measurements and Raman spectroscopy. The high workfunctions of Nickel and Palladium form an ohmic contact with the CNT valence band, but the contact properties change on Hydrogen exposure due to a reduction in the PdNi workfunction and the realignment of the PdNi Fermi level with the CNT band structure. A PdNi contacted semiconducting CNT exhibited significantly lower currents after Hydrogen exposure while a metallic CNT exhibited a small current increase. The semiconducting and metallic natures of the CNTs are confirmed by their Raman spectra. This study demonstrates a technique for modulating the PdNi-CNT contact and differentiating between semiconducting and metallic CNTs via contact modulation. It also provides experimental evidence of the theoretical allocation of features in the CNT Raman spectra. 1. Introduction Carbon nanotubes (CNTs), along with other carbon allotropes such as Graphene and Fullerenes, have sparked great interest in a multitude of research fields owing to their low dimensionality [1] and excellent electrical, mechanical, and thermal properties as well as high surface area to volume ratio [2]. The occurrence of metallic and semiconducting CNTs and demonstration of ballistic electron transport [3] have led to intense research into their use to further miniaturise electronic transistors, leading to all-Carbon circuits [4]. The ballistic electron transport also makes them an attractive material for spintronic devices [5], where electron spin is conserved by the absence of collision events. The high electronic conductivity and almost complete optical transparency of Graphene have led researchers to investigate its use as a transparent electrode [6] to replace the expensive Indium Tin Oxide (ITO). Innovative uses stemming from filling of hollow CNTs for use as battery anodes [7] and formation of high mechanical strength aerogels from Graphene [8] reveal the wide variety of applications possible with these versatile forms of Carbon. Despite this promise, significant problems in production, positioning, and differentiation between metallic and semiconducting CNTs remain before individual CNT-based electronic devices become commercially viable. Studies that investigated the performance of transistors based on individual CNTs have found that the metal-CNT contacts play an important role in the device behaviour [9, 10]. The importance of metal-CNT contacts is further highlighted by Zhang et al. [11], who demonstrated a doping-free
%U http://www.hindawi.com/journals/jns/2014/404519/