Gate voltage dependent characteristics of p-n diodes and bipolar transistors based on multiwall CN(x)/carbon nanotube intramolecular junctions

Recent Developments in Single-Walled Carbon Nanotube Thin Films Fabricated by Dry Floating Catalyst Chemical Vapor Deposition

Transparent conducting films (TCFs) are critical components of many optoelectronic devices that pervade modern technology. Due to their excellent optoelectronic properties and flexibility, single-walled carbon nanotube (SWNT) films are regarded as an important alternative to doped metal oxides or brittle and expensive ceramic materials. Compared with liquid-phase processing, the dry floating catalyst chemical vapor deposition (FCCVD) method without dispersion of carbon nanotubes (CNTs) in solution is more direct and simpler. By overcoming the tradeoff between CNT length and solubility during film fabrication, the dry FCCVD method enables production of films that contain longer CNTs and offer excellent optoelectronic properties. This review focuses on fabrication of SWNT films using the dry FCCVD method, covering SWNT synthesis, thin-film fabrication and performance regulation, the morphology of SWNTs and bundles, transparency and conductivity characteristics, random bundle films, patterned films, individual CNT networks, and various applications, especially as TCFs in touch displays. Films based on SWNTs produced by the dry FCCVD method are already commercially available for application in touch display devices. Further research on the dry FCCVD method could advance development of not only industrial applications of CNTs but also the fundamental science of related nanostructured materials and nanodevices.

O2 Plasma Etching and Antistatic Gun Surface Modifications for CNT Yarn Microelectrode Improve Sensitivity and Antifouling Properties

Carbon nanotube (CNT) based microelectrodes exhibit rapid and selective detection of neurotransmitters. While different fabrication strategies and geometries of CNT microelectrodes have been characterized, relatively little research has investigated ways to selectively enhance their electrochemical properties. In this work, we introduce two simple, reproducible, low-cost, and efficient surface modification methods for carbon nanotube yarn microelectrodes (CNTYMEs): O2 plasma etching and antistatic gun treatment. O2 plasma etching was performed by a microwave plasma system with oxygen gas flow and the optimized time for treatment was 1 min. The antistatic gun treatment flows ions by the electrode surface; two triggers of the antistatic gun was the optimized number on the CNTYME surface. Current for dopamine at CNTYMEs increased 3-fold after O2 plasma etching and 4-fold after antistatic gun treatment. When the two treatments were combined, the current increased 12-fold, showing the two effects are due to independent mechanisms that tune the surface properties. O2 plasma etching increased the sensitivity due to increased surface oxygen content but did not affect surface roughness while the antistatic gun treatment increased surface roughness but not oxygen content. The effect of tissue fouling on CNT yarns was studied for the first time, and the relatively hydrophilic surface after O2 plasma etching provided better resistance to fouling than unmodified or antistatic gun treated CNTYMEs. Overall, O2 plasma etching and antistatic gun treatment improve the sensitivity of CNTYMEs by different mechanisms, providing the possibility to tune the CNTYME surface and enhance sensitivity.

The effects of contacts and ambipolar electrical transport in nitrogen doped multiwall carbon nanotubes

The electrical transport properties of pristine single wall carbon nanotubes (SWCNTs) and lower nitrogen content doped multiwall carbon nanotubes (MWCNTs) (lower than in the experiments of Xiao et al (2005 J. Am. Chem. Soc. 127 8614)) in contact with Au and Pt were studied. Compared with pristine SWCNTs, the Fermi level of the lower nitrogen content doped MWCNTs also moved to the valence band edge with the contact metal's work function increasing. In contrast to Derycke et al' s results (2002 Appl. Phys. Lett. 80 2773), the lower nitrogen content doped MWCNTs exhibited ambipolar behavior, and increasing the doping level led to a reduction of the Schottky barrier height of electrons. Consistent with theoretical calculations, the results support the opinion that the degree of Fermi level pinning is minor for doped carbon nanotubes.