Semiconductors, single walled carbon nanotubes

The process begins with the synthesis of different semiconductor nanomaterials (e.g., single-walled carbon nanotubes and single-crystalline nanowires/... 

Single-walled carbon nanotubes (SWNTs) can behave as semiconductors or metals, depending on their chirality. Therefore, vibrational spectroscopy is indispensable for characterizing chemical stmctures. Especially, resonance Raman spectroscopy is ccai-sidered to be one of most powerful tools, which provides us rich information about nanotube diameters or defect densities [10, 27, 39]. However, much more detailed characterization is required for further development of carbon-based nanotechnology. 

Inorganic semiconductor nanoparticles have also been implemented as electron acceptors. For example, CdSe, CnInSc2 and PbS have been of interest becanse they absorb in the visible and can extend the blend absorption ont to the near infrared (Huynh et al, 2002 Sun et al, 2003), as discussed in Section 7.4.4. In one study, CdSe nanoparticles were combined with single-walled carbon nanotubes for improved light harvesting and as material variations for BHJ devices (Robel et al, 2005). 

Single-walled carbon nanotubes (SWNT) may be either conductors or semiconductors depending upon the tube diameter and the chiral angle of the fused benzene rings with respect to the lube axis. Van der Waals forces cause SWNT to slick together in clumps, which are normally mixtures of conductors and semiconductors. SWNT stick to many surfaces and they bend, or drape, around nano-sized features that are upon a surface. 

N. Izard, S. Kazaoui, K. Hata, T. Okazaki, T. Saito, S. lijima, andN. Minami, Semiconductor-enriched single wall carbon nanotube networks applied to field effect transistors, Appl. Phys. Lett, 92, 243112 (2008). 

Milestone Five is as follows. When a single-walled carbon nanotube (SWCWT) was deposited by Louis Pasteur s method onto a Si substrate with a 70-nm-wide Au source and drain electrodes, and was studied by STM (Fig. 7), with the STM tip acting as a gate electrode, the nanotube acted as a semiconductor. 

Single-walled carbon nanotubes (SWNT) were proposed as nanoscale electromechanical pressure sensors [6]. It was demonstrated by computation that a pressure induced a reversible shape transition in armchair SWNTs, which in turn induced a reversible electrical transition from metal to semiconductor. The potential long lifetime nature of this pressure sensor due to the excellent mechanical durability of the carbon nanotubes was pointed out as a superior aspect. SWNTs can also be used, besides as pressure sensors, as mass, strain, and temperature sensors by sensing the resonant frequency shift of a carbon nanotube resonator when it is subjected to changes in attached mass, external loading, or temperature [7, 8]. The feasibility of such a sensor was illustrated by means of computer... 

Under ambient conditions, SWNTs are p-type semiconductors. This means that the charge carriers are holes, or the absence of electrons. This class of semiconductors shows an increase in conductivity when electron density is withdrawn and a decrease in conductivity when electron density is donated. This behavior has been observed experimentally for individual SWNTs connected to a set of electrodes. This allows for chemical detection with a simple chemiresistor. This is a device composed of two electrodes which are connected by some material, in this case a single-walled carbon nanotube, which changes resistance upon exposure to a particular analyte. 

Recall the single-walled carbon nanotubes (SWNT) discussed in Section 13.1.8. Because of their highly extended ir systems, they are conductive materials. In fact, depending on the precise structure, SWNT behave as semiconductors or true metallic conductors even without doping . 

Beside their well-known extra-high mechanical properties, single-walled carbon nanotubes (SWNTs) offer either metallic or semiconductor characteristics based on the chiral structure of fullerene. They possess superior thermal and electrical properties so SWNTs are regarded as the most promising reinforcement material for the next generation of high performance structural and multifunctional composites, and evoke great interest in polymer based composites research. The SWNTs/polymer composites are theoretically predicted to have both exceptional mechanical and functional properties, which carbon fibers cannot offer [105]. 

Kongkan A, Kamat PV (2007) Electron storage in single wall carbon nanotubes. Fermi level equilibration in semiconductor—SWCNT suspensions. ACS Nano 1 13-21... 

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