Product Code: ICAL06_M1106

Aligned Synthesis of Carbon Nanotubes by Laser-assisted Chemical Vapor Deposition
Authors:
J Shi, University of Nebraska; Lincoln NE USA
K.J. Yi, University of Nebraska; Lincoln NE USA
Y.F. Lu, University of Nebraska; Lincoln NE USA
Presented at ICALEO 2006

With the recent advances of the aligned and position-controlled growth of carbon nanotubes (CNTs), there have been intensive studies in the optimizing of growth process for fabrication of various CNT-based electronic devices. Using conventional thermal chemical vapor deposition (CVD) method, substrates as well as the chamber need to be globally heated to sufficient high reaction temperature. In this study, we developed a new method to directly synthesize CNTs across pre-defined electrodes on silicon wafers using laser-assisted chemical vapor deposition (LCVD), which can induce local and instant heating at the desired positions. A CW CO2 laser (Synrad Inc, 10.6 µm) as well as a CW Nd:YAG laser (Quantronix Inc, 1064 nm) were used. The carbon feedstock was NH3/C2H2 gas mixtures (volume ratio 10/1), with a process pressure of 80 Torr. Mo electrodes were patterned on silicon substrates by photolithography and focused ion beam. The catalyst islands, which consisted of Fe/Mo nanoporous structures (Fe(NO3)3.9H2O, MoO2(acac)2 and alumina nanoparticle mixtures) were then transferred to on the electrodes. The substrate temperature was around 700 oC, monitored by a pyrometer. Laser irradiation lasted for 3 to 6 min. Single-walled carbon nanotubes (SWNTs) bridging the electrodes were synthesized. Raman spectra indicated that the diameters of the synthesized SWNTs were from 1.2 - 1.4 nm. Electrical properties were characterized by measuring source-drain current against the gate and the source-drain voltage, i.e., Ids-Vg and Ids-Vds respectively. I-V characterization showed that the SWNTs synthesized were mainly semiconducting.