RESEARCH ARTICLE Copyright © 2012 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Computational and Theoretical Nanoscience Vol. 9, 1554-1557, 2012 Schottky Current in Carbon Nanotube-Metal Contact Sara Sangtarash 1 , Hatef Sadeghi 1 , M. T. Ahmadi 1? ∗ , M. H. Ghadiry 1 , Sohail Anwar 2 , and Razali Ismail 1 1 Faculty of Electrical Engineering, UniversitiTeknologi Malaysia, Skudai 81310, Johor Baharu, Malaysia 2 Pennsylvania State University, Altoona College, USA Silicon based technology has received its technical limitation because of its unstable structure at nano-level. Carbon nanotube as an alternative material has attracted significant scientific efforts. Fabrication of Schottky diode using carbon nanotube is an open area of research to overcome this limit. In this study, we model the current of CNT Schottky diode under applied voltage. Parabolic band approximation on CNT induces Fermi-Dirac integral of order zero on its current voltage which is similar to the conventional one dimensional material. This model shows that its current has a weak dependence on temperature corresponding to the small applied voltage. It is quite different in high bias voltages which are independent of temperature. Based on this model, incremental effect of the carbon nanotube diameter has been explained by increasing the current with the applied voltage. The model presented in this paper is in good agreement with the reported data from experiments. This device can be used in the integrated circuit miniaturization. Keywords: Carbon Nanotube, Schottky Contact, Schottky Current, Modeling. 1. INTRODUCTION Schottky barrier is known as moving the barrier (electrons) from the metal into the semiconductor. For the first time, Schottky demonstrated that a potential barrier formed at a metal-semiconductor junction has the rectification charac- teristics and thus it is suitable for use as a diode. Lower junction voltage and a decreased depletion width in the metal are the two key differences between a p–n junc- tion and a Schottky barrier. The lower junction voltage in Schottky barrier means that the ideal diode approxima- tion can be used for it. Due to their low junction voltage, Schottky barriers are used in applications where a device that closely approximates an ideal diode is needed. They are also used with normal diodes and transistors for cir- cuit protection. Connection of a metal or silicide layer to a doped semiconductor layer forms a Schottky diode where Schottky junction (or Schottky barrier) is formed at the junction. 1? 2 Carbon nanotubes (CNTs) offer a unique structure which can be modeled as a one-dimensional quantum wire. Because of their excellent electrical, mechanical, and chemical properties, carbon nanotubes have been of great interest to the researchers in basic sciences and technology. 3 They have shown a great potential for next- generation electronic applications. Many devices such as ∗ Author to whom correspondence should be addressed. carbon nanotube field-effect transistors, CNT diodes, sin- gle electron transistors, nanoelectrodes, and several others have been built from carbon nanotubes. 4–6 Furthermore, nanotubes’ properties such as high carrier mobility, long mean free path, and the potential of carrying high current density (equal to or better than the currently used materials), have attracted researchers to develop alter- native devices to improve performance or to explore the limitation of traditional structure. 6–9 A cylindrical single-wall CNT (SWCNT) consists of one atom in thickness of graphite (called graphene) which is rolled up into a cylinder as shown in Figure 1. The diameter of the tube is typically 1.4 nm. 9? 10 When the dia- meter of cylinder is less than the De-Broglie wave length, it can be estimated as a one dimensional. The band struc- ture of one dimensional shows the parabolic behavior near the minimum band energy with wave vector. Multi-walled nanotubes (MWNT) consist of multiple rolled layers of graphite. 11? 12 Based on the diameter and the helicity of the arrange- ment of the graphitic rings in Carbon nanotubes walls, it can be found as either metallic or semiconducting. The diameter and the helicity of a defect-free SWNT are defined by Chiral vector or C h = na 1 + ma 2 , where a 1 and a 2 are the graphene lattice unit cell base vectors and n and m are the different integer values for each type of tube (Fig. 2). According to chirality, the graphene sheet can be rolled to form armchair tubes that are metallic J. Comput. Theor. Nanosci. 2012, Vol. 9, No. 10 1546-1955/2012/9/001/004 doi:10.1166/jctn.2012.2243 1