Towards crossbar nanoarray structure via microcontact printing

The method for patterning arrays of multiwalled carbon nanotubes (MWCNT's) in symmetric patterns to form junctions has been demonstrated. This has been achieved by incorporating the technique of microcontact printing using poly-dimethylsiloxane (PDMS) molds. Relief structures in the order of a few micrometers were fabricated that enabled the transfer of continuous horizontal arrays of MWCNT's in aqueous suspension in a controlled manner. The MWCNT's were patterned onto silicon microelectrode substrates with metallic gold electrodes. These were fabricated using standard photolithography techniques. The silicon substrates served as a base platform with suitable measurement microelectrodes for electrically characterizing the crossbar junction arrays. Using a dual alignment and stamping process, PDMS molds were inked alternatively with p-type and n-type suspensions of MWCNT's and transferred in a grid-like manner onto the base platform. Parallel alignment of the MWCNT's was achieved due to the geometry of the mold relief structures. This step-by-step assembly resulted in the formation of crossbar MWCNT array structures. Each of these crosspoints in the individual junction can function as an addressable crossbar nanodevice. The functionality of this circuit was demonstrated through the current-voltage (I-V) characteristics. Using these high-density crossarray circuit patterns, addressable nanostructures that form the building blocks of highly integrated device arrays can be built.