We fabricated the cross-junction arrays of p-type single walled carbon nanotube (SWCNT) and n-type V2O5 nanowire (NW) network percolation channels with a width of a few µm, and then measured the electrical properties for their application to nano-devices. In the fabrication, SWCNTs and V2O5 NWs could be positioned on the desired sites of the substrates with preferred orientation via two independent soft lithography procedures.
First, poly-methylmethacrylate (PMMA) patterns were transferred onto 3-aminopropyltriethoxy (APS)-treated SiO2 substrate by stamping poly(dimethylsilioxane) (PDMS) stamp inked with Langmuir-Schaeffer films of PMMA. Second, preferential adsorption of SWCNTs on the APS-treated area was performed during tilted-drop casting,1 where the PMMA patterns worked as successful passivation layers. Third, the PMMA patterns were removed by lift-off method using acetone. SWCNTs were commonly aligned along the direction parallel with the line pattern and more distinctly showed such behavior where the width of the APS region was as small as ~1 µm.
For the patterning of V2O5 NWs, direct stamping of V2O5 NW inked PDMS stamp,2 which had been modified to be hydrophilic by ultraviolet-ozone (UVO)-treatment, onto the SiO2 substrate was done. Interestingly, V2O5 NWs were aligned perpendicular to the long axis of line pattern, when the average length of the V2O5 NW was longer than the width of the PDMS stamp.
Integration of the above-mentioned two soft lithography processes produced the cross-junction arrays of SWCNTs and V2O5 NWs, where the printing of V2O5 NW patterns perpendicular to the previously patterned SWCNTs was performed.
On this p-n junction arrays, Au-source and Ti/Au-drain electrodes were deposited onto SWCNTs and V2O5 NW patterns, respectively by e-beam lithography and the electrical junction properties were measured between SWCNTs and V2O5 NWs network percolation channels. Such formed contact junction showed the rectifying behavior similar to that observed in the conventional Si p-n diodes.
(1) H. Ko, V. V. Tsukruk, V. V. Nano Lett. 6 1443 (2006).
(2) Y.-K. Kim, S. J. Park, J. P. Koo, D.-J. Oh, G. T. Kim, S. Hong, J. S. Ha Nanotechnology 17 1375 (2006).
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