Precise positioning of single-walled carbon nanotubes by ac dielectrophoresis

Abstract

The precise placement of single-walled carbon nanotubes ͑SWCNTs͒ in device architectures by ac dielectrophoresis involves the optimization of the electrode geometry, applied voltage and frequency, load resistance, and type of nanotube sample used. The authors have developed a toolkit to controllably integrate SWCNTs in device structures by the use of floating potential metal posts and appropriate electrode geometries, as designed using electric field simulations, and used it to fabricate structures such as crossed nanotube junctions.

Local-gated single-walled carbon nanotube field effect transistors assembled by AC dielectrophoresis

“…The two terminal resistance of our samples is usually in the range of 1-10 Mohm. Our value of contact resistance is consistent with other DEP assembled devices [14][15][16][17][18][19][20][21][22][23][24][25], however, higher than that of top contact CVD grown devices (~ 100 kOhm), where the nanotube is first grown by CVD on a substrate, made contact to, and then annealed. The contact resistance depends on several factors such as work function of the metal being used, diameter of the nanotubes, surface properties, contact area and device geometry.…”

“…After the trapping process is complete, the chip is rinsed with IPA and blow dried with nitrogen gas to remove any unwanted nanotubes or impurities in the suspension. Other groups have dispersed CNT in an aqueous sodium dodecyl sulfate (SDS) [14][15][16][17][18][19][20]23], isopropyl alcohol (IPA) [21], dimethylformamide (DMF) [24], and DCE [25] for DEP assembly. Although an aqueous SDS solution has been used most frequently and has been shown to disperse CNT well, it is not compatible with our device fabrication process.…”

“…In DEP, CNTs are assembled from solution using a non-uniform AC electric field. However, all DEP assembled CNT-FETs reported in the literature used only a global back gate [14][15][16][17][18][19][21][22]24]. Global back gated devices give poor device performance due to inefficient gate coupling and contact-controlled operation.…”

Controlling SWCNT assembling density by electrokinetics

“…However due to their nanoscale characteristics and the diversity in electrical properties in SWCNTs, it is more challenging to fabricate SWCNT-based nanodevices [5][6][7]. To date several methods have been developed to integrate SWCNTs into nanodevices such as nanomanipulation using an atomic force microscopy (AFM), contact printing and dielectrophoresis (DEP) [8][9][10]. * Corresponding author at: Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong.…”

Magnetophoretic assembly and printing of nanowires

“…With this in mind, two methods have been described using either oriented electric or magnetic fields. For materials with a sufficiently strong dielectric response, the phenomena of dielectrophoresis has been used to create silicon interconnects as described by WissnerGross 5 and carbon nanotube structures by Bannerjee et al 6 . Similarly, nanowires which are ferromagnetic in nature, or have ferromagnetic ends, can be attracted to and oriented by, magnetized tracks patterned onto a flat substrate as shown by Hangarter and Myung 7 in the case of segmented nanowires viz.…”