Authors: X. Yang, D.W. Austin, M.A. Guillorn, V.I. Merkulov, A.V. Melechko, D.H. Lowndes and M.L. Simpson
Affilation: Oak Ridge National Laboratory, United States
Pages: 342 - 345
Keywords: nanotechnology, device, nanofiber, transport
We are fabricating active nanoscale electronic devices based on Vertically Aligned Carbon Nanofibers (VACNF). VACNFs are synthesized in a high-density Plasma-Enhanced Chemical Vapor Deposition (PECVD) process that provides a high degree of control of the growth conditions and, consequently, the resultant electronic properties of the nanofibers. We have described this process in detail elsewhere(1-3). Figure 1 illustrates the device fabrication process. For these devices, the VACNF was grown to a height of ~ 1 mm, the base diameter was ~ 200-300 nm, and the tip diameter was ~ 40-70nm. In previous work we demonstrated that VACNFs may be subjected to Chemical Mechanical Polishing (CMP) and Reactive Ion Etching (RIE) without observable damage [4,5]. Figure 2 shows AFM and SEM images demonstrating that the fiber tip is encased in the upper electrode metal in the completed device. The silicon substrate served as the bottom contact and the patterned Ti/Au electrode for top contact. We reproducibly find a rectifying schottky behavior in these devices as shown in Fig 3. We speculate that this junction is located at the bottom of the nanofiber at the interface with the silicon substrate. The nanofibers are quite robust and can sustain 100uA current without damage. From the temperature sweep measurements, we calculate a barrier height of about 300mV. We have preliminary data that suggest we may be able to modulate this barrier height by changing VACNF chemical composition through the control of the PECVD growth process. We will describe our wafer-scale process for fabricating these vertical nanoscale electronic devices, present I-V characteristics, and demonstrate how the VACNF growth process can be manipulated to produce devices with different characteristics.
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