Narrow-gap semiconductive

Tube (3a, 0) will have the bond pattern of Alt 2 and be narrow-gap semiconductive. 

The result indicates the presence of metallic, narrow-gap semiconducting and/or semimetallic CNTs and is in agreement with theoretical predictions [2-7]. The... 

Kertesz, M., and Y.-S. Lee. 1987. Energy gap and bond length alternation in heterosubstituted narrow gap semiconducting polymers. J Phys Chem 91 2690-2692. 

The structure of CaB contains bonding bands typical of the boron sublattice and capable of accommodating 20 electrons per CaB formula, and separated from antibonding bands by a relatively narrow gap (from 1.5 to 4.4 eV) . The B atoms of the B(, octahedron yield only 18 electrons thus a transfer of two electrons from the metal to the boron sublattice is necessary to stabilize the crystalline framework. The semiconducting properties of M B phases (M = Ca, Sr ", Ba, Eu, Yb ) and the metallic ones of M B or M B5 phases (Y, La, Ce, Pr, Nd ", Gd , Tb , Dy and Th ) are directly explained by this model . The validity of these models may be questionable because of the existence and stability of Na,Ba, Bft solid solutions and of KB, since they prove that the CaB -type structure is still stable when the electron contribution of the inserted atom is less than two . A detailed description of physical properties of hexaborides involves not only the bonding and antibonding B bands, but also bonds originating in the atomic orbitals of the inserted metal . ... 

A. M. Myasnikov and N. N. Gerasimenko, Ion Implantation and Thermal Annealing of III-V Compound Semiconducting Systems Some Problems of III-V Narrow Gap Semiconductors... 

The aqueous corrosion of ceramics may involve a charge-transfer or electrochemical dissolution process. However, in many cases, dissolution or corrosion may take place with no charge transfer yet may be determined by one or more electrochemical factors such as absorbed surface charge or electronic band bending at the surface of narrow-band-gap semiconducting ceramics. The aqueous corrosion of ceramics is important in a number of areas. One of the most important is the stability of passive oxide films on metals. The stability of ceramics is a critical aspect in some aqueous photoelectrochemical applications (12), an example being the photoelectrolytic decomposition of water. Structural, nonoxide ceramics such as SiC or Si3N4 are unstable in both aqueous acid and alkaline environments the latter is virtually unstudied, however. 

Jenekbe, S.A. 1986. A class of narrow-band-gap semiconducting polymers. Nature 322 345-347. 

Havinga, E.E., W. ten Hoeve, and H. Wynberg. 1993. Alternate donor-acceptor small band-gap semiconducting polymers Polysquaraines and polycroconaines. Synth Met 55-57 299-306. Lambert, T.M., and J.P. Ferraris. 1991. Narrow band gap polymers Polycyclopenta[2,l-b 3,4-b ]dithiophene-4-one. / Chem Soc Chem Commun 752-753. 

A typical semiconducting material is silicon. It crystallises in the diamond lattice (Fig. 1-26) but unlike diamond its band gap is narrow enough (1.12 eV) to make it semiconducting. 

These factors, in turn, are dependent on the diameter and helicity. It has been found that metallicity occurs whenever (2n + m) or (2 + 2m) is an integer multiple of three. Hence, the armchair nanotube is metallic. Metallicity can only be exactly reached in the armchair nanotube. The zigzag nanombes can be semimetallic or semiconducting with a narrow band gap that is approximately inversely proportional to the tube radius, typically between 0.5 -1.0 eV. As the diameter of the nanombe increases, the band gap tends to zero, as in graphene. It should be pointed out that, theoretically, if sufficiently short nanotubes electrons are predicted to be confined to a discrete set of energy levels along all three orthogonal directions. Such nanotubes could be classified as zero-dimensional quantum dots. 

At present the IV-VI series of semiconducting materials comprises a number of the most promising materials for IR applications [1-4]. An interest in these materials is primarily because they are narrow band gap semiconductors and therefore have the potential to be employed in devices as optically active components in the near-infrared (NIR) and infrared (IR) spectral region and are hence beneficial to applications for solar cells, detectors, telecommunications relays, etc. The interest in the IV-VI materials has also grown in recent years because of the observation that they are thought to demonstrate efficient multiple exciton generation (MEG) [3,5-7]. This has implications for the efficiencies of solar cells and other applications based on these materials, especially as it provides a means by which the Shockley/Queisser efficiency limit may be overcome. 

Lead sulfide (PbS) is a narrow band gap semiconductor used for many optical applications, like IR detectors [1], It is well known that semiconducting properties of PbS can be tailored by reducing the size of particles down to the nanometer scale. Semiconducting properties are greatly affected by the atomic structure. However, the atomic structure of nanoparticles may not be the same as the structure of the same substance in bulk. This paper focuses on study of the atomic structure of PbS nanoparticles. 

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