We report the synthesis, structure, spectroscopic properties, charge and thermal transport, and electronic structure of a new member of the Zintl family, Yb(5)Al(2)Sb(6). The compound crystallizes in the Ba(5)Al(2)Bi(6) structure type and requires the addition of Ge or Si in the synthesis, which appears to act as a catalyst. Yb(5)Al(2)Sb(6) has an anisotropic structure with infinite anionic double chains cross-linked by Yb(2+) ions. Polycrystalline ingots of Yb(5)Al(2)Sb(6) prepared in the presence of 0.5 mol equiv of Ge showed room-temperature conductivity, thermopower, and thermal conductivity of approximately 1100 S/cm, approximately 20 microV/K, and approximately 3.8 W/m.K, respectively. Investigations of other solid solutions of Yb(5)Al(2)Sb(6), doping effects, and chemical modifications are discussed. Sr only partially replaces Yb in the structure leading to Sr(0.85)Yb(4.15)Al(2)Sb(6). Electronic structure calculations performed using a highly precise full-potential linearized augmented plane wave method within the density functional theory scheme show the presence of a negative band gap and suggest incomplete electron transfer and a metallic character to the compound.

A light-emitting diode is fabricated and characterized on a semiconducting serpentine CNT which has many parallel segments with identical chirality. Compared with the individual CNT and CNT-film devices, the device with parallel segments shows improvement of an order of magnitude in current, significantly larger electroluminescent intensity, and narrower emission bands. Serpentine nanotubes are an ideal choice for practical applications of CNT-based light sources.

Ytterbium I 4100Synthesis, Structure and Charge Transport Properties of Yb5Al2Sb6: A Zintl Phase with Incomplete Electron Transfer. -The title compound is obtained in high yields directly from the elements in the presence of a catalytic amount of Ge (950°C, 2 d) or by arc melting under an Ar atmosphere. The samples are characterized by single crystal XRD, charge transport measurements, and FLAPW electronic band structure calculations. Yb5Al2Sb6 and Sr0.85Yb4.15Al2Sb6 (obtained by partial replacement of Yb by Sr) crystallize in the orthorhombic space group Pbam with Z = 2. Yb 5 Al 2 Sb 6 has an anisotropic structure with infinite anionic double chains cross-linked by Yb 2+ ions. It shows a room temperature conductivity of about 1100 S/cm, a thermopower of 20 µV/K, and a thermal conductivity of 3.8 W/m·K. -(TODOROV, I.; CHUNG, D. Y.; YE, L.; FREEMAN, A. J.; KANATZIDIS*, M. G.; Inorg.

We fabricate carbon nanotube (CNT)-field effect transistors (FETs) with a changeable channel length and investigate the electron transport properties of single-walled, double-walled and triple-walled CNTs under uniaxial strain. In particular, we characterize the atomic structure of the same CNTs in the devices by transmission electron microscopy and correlate the strain-induced electronic property change to the chirality of the CNTs. Both the off-state resistance and on-state resistance are observed to change with the axial strain following an exponential function. The strain-induced band gap change obtained from the maximum resistance change in the transfer curve of the ambipolar FETs is quantitatively compared with the previous theoretical prediction and our DFTB calculation from the chirality of the CNTs. Although following the same trend, the experimentally obtained strain-induced band gap change is obviously larger (57%-170% larger) than the theoretical results for all the six CNTs, indicating that more work is needed to fully understand the strain-induced electronic property change of CNTs.