Fabrication of single-walled carbon nanotube Schottky diode with gold contacts modified by asymmetric thiolate molecules

Abstract

We have fabricated single-walled carbon nanotube (SWCNT) Schottky diodes by asymmetrically modifying the two Au/SWCNT contacts using different thiolate molecules, methanethiol (CH3SH) and trifluoroethanethiol (CF3CH2SH). Characterization has revealed that highly asymmetrical contacts with Schottky barrier heights of ∼190 and ∼40 meV (increased by over 70% and decreased by over 60%, respectively with respect to that of pristine Au/SWCNT contact of ∼110 meV) were achieved for the Au/SWCNT contacts modified by CH3SH and CF3CH2SH, respectively. The performance of our SWCNT Schottky diodes is as follows: the forward and reverse current ratio (Iforward/Ireverse) higher than 104, a forward current as high as ∼5 μA, a reverse leakage current as low as ∼100 pA, and a current ideality factor as low as ∼1.42. This is at least comparable to, if not better than SWCNT Schottky diodes fabricated with asymmetrical metals, where one contact is a metal with a work function lower than that of SWCNTs to yield a Schottky contact, while the other has a work function higher than that of SWCNTs to achieve an ohmic (more near ohmic) contact. © 2009 Elsevier Ltd. All rights reserved.