A Scalable, CMOS‐Compatible Assembly of Ambipolar Semiconducting Single‐Walled Carbon Nanotube Devices

Abstract

Recent success in the high-purity separation of semiconducting single-walled carbon nanotubes (sSWNTs) allows for the development of large-scale nanotube electronics. Here, it is demonstrated that alternating-current dielectrophoresis can assemble high-density, multidirectional arrays of sSWNTs. A 99% pure solution of arc-discharge sSWNTs (mean diameter of 1.4 nm), fractionated by density-gradient ultracentrifugation, is used in the process because it has been shown to have the most desirable performance for nanotube electronics. Annealing is used to degrade the surfactant after assembly, resulting in reduced nanotube-metal contact resistance and higher on-off ratio. Devices fabricated on a hydrophobic parylene surface show ambipolar transport and reduced hysteresis in the transfer characteristics. Together, these steps lead to scalable, CMOScompatible integration of ambipolar sSWNT devices.SWNTs form a family of versatile quasi 1D systems, [ 1 ] exhibiting electronic structure ranging from zero bandgap metal to semiconducting with bandgaps up to 1.5 eV. [ 2 ] Carbon nanotubes (CNTs) have been shown to outperform conventional copper interconnects and silicon fi eld-effect transistors (FETs) as individual devices. [ 3 , 4 ] As a result, high-performance all-nanotube electronic circuits could be fabricated from metallic SWNT interconnects and semiconducting SWNT transistors. The practical realization of such circuits, however, is hindered by limited available routes for large-scale integration [ 5 , 6 ] and the polydispersity of as-grown SWNTs. SWNTs are typically synthesized as a mixture of multiple chiralities, with varied electronic properties due to strong structure-property correlation, [ 7 ] i.e., their bandgap is related directly to chirality. The ( n , m ) notation of chirality is used here to identify SWNTs. Individual SWNTs have been directly grown with desired location and orientation by an in situ electric-fi eld, [ 8 , 9 ] gasfl ow, [ 10 ] or substrate-mediated alignment. [ 11 ] While some control over growth conditions has been achieved in limiting the diameter distribution of the SWNTs and consequently the possible chiralities, [ 12 , 13 ] the polydispersity still remains. This, coupled with the high growth temperatures required, which are incompatible with CMOS technology, rules out directly growing chirality-specifi c SWNTs at predetermined locations in an integrated circuit.The alternate approach is bottom-up assembly of a controlled number of SWNTs with desired electronic properties at specifi c locations and orientation. The challenge was defi ned by McEuen in 2000 [ 6 ] and has to be achieved to realize SWNT-based integrated microelectronic circuits. Signifi cant recent advances have been made in individually dispersed SWNT suspensions [ 14 ] and solution-phase sorting of SWNTs [15][16][17][18][19][20][21][22] by length, diameter, whether they are metallic or semiconducting, and even chirality; therefore, a combination of solution-phase sorting with advanced bottom-up assembly presents a pr...

A theoretical study on the interaction of amphetamine and single-walled carbon nanotubes

“…In outset, we obtained optimized geometries of amphetamine and pure armchair (4,4), (5,5), (6,6), (7,7) SWCNTs in the gas phase that are shown in the figure 1. A closer look at the figure 1 indicates that for the amphetamine molecule in the most stable form; the amino group is perpendicular to phenyl group.…”

“…We constructed four armchair nanotubes: (4,4) consisting of 96 atoms of carbon and 16 atoms of hydrogen, (5,5) consisting of 120 C atoms and 20 H atoms, (6.6) consisting of 144 C and 24 H atoms and (7,7) consisting of 168 C and 28 H with diameters about 5.42 Å, 6.78 Å, 8.14 Å and 9.40 Å, respectively that in which the ends of nanotubes were saturated by hydrogen atoms and a subscription in 6 unit cells.…”

“…According to these values, if we disregard the adsorption related to (4,4) SWCNT, we can see a specific trends between increase in diameter of CNTs and enhancement of adsorption energy. By investigating in values of HOMO-LUMO for this configuration, further adsorption of (4,4) compared to (5,5) and (6,6) nanotubes probably depends on the amount of the created band gap by LUMO of the amphetamine and HOMO of (4,4) CNT (See Table 2). In figure 4 you can see the change in energy of the complex versus change in distance of the amphetamine on the surface of nanotube in parallel mode.…”

“…Because of their unique properties such as large surface area, field emission, and electrochemical properties, and other physical and chemical features, they have a lot of potential applications in different fields [2][3][4][5][6]. Many works is done to survey the properties and the usage of these extraordinary new materials [7,8].…”

Dielectrophoresis‐Assisted Integration of 1024 Carbon Nanotube Sensors into a CMOS Microsystem

“…[30] The floating electrodes, which are connected to the common electrode through CNTs accumulate less charge during SEM imaging and appear darker than electrodes without CNT connection. VC-SEM has been previously used to study single connections or a few devices, [31,32] here we propose to use it for large CNT arrays.…”