Superconductivity in the RexMo6S8

The rare earth molybdenum sulfides RE_xMo₆S₈ (RE = rare earth) have been synthesized and are found to be superconducting with a few exceptions. This result, which is surprising in view of the high concentration of magnetic ions, is correlated with the particular structure of these compounds based on on units of Mo₆S₈.     

One-dimensional condensation of Mo6 octahedral clusters: A new cluster,Mo12, and a new building block,Mo12S14, in M2Mo9S11

Two new Mo compounds, Tl₂Mo₉S₁₁ and K₂Mo₉S₁₁, have been found. The structure of these compounds is characterized by the presence of a completely new building block, Mo₁₂S₁₄, in addition to the well-known Mo₆S₈ unit as in the PbMo₆S₈-type compounds. The new cluster, Mo₁₂, contained in the Mo₁₂S₁₄ unit can be considered as a one-dimensional condensation of three Mo₆ octahedral clusters. These new materials, the structure of which resembles that of PbMo₆S₈, are metallic but are not superconducting above 2.1°K.     

互联网与图书馆的发展

本文从互联网的特点入手,分析了互联网对图书馆的影响,并对图书馆的未来发展方向进行了探讨.     

Amorphouslike density of gap states in single-crystal pentacene

We show that optical and electrical measurements on pentacene single crystals can be used to extract the density of states in the highest occupied molecular orbital-lowest unoccupied molecular orbital band gap. It is found that these highly purified crystals possess band tails broader than those typically observed in inorganic amorphous solids. Results on field-effect transistors fabricated from similar crystals imply that the gap state density is much larger within 5-10 nm of the gate dielectric. Thus, organic thin-film transistors for such applications as flexible displays might be significantly improved by reducing these defects.     

Bias-dependent generation and quenching of defects in pentacene

We describe a defect generation phenomenon that is new to organic semiconductors. A defect in pentacene single crystals can be created by bias-stress and persists at room temperature for an hour in the dark but only seconds with 420 nm illumination. The defect gives rise to a hole trap at Ev+0.38 eV and causes metastable transport effects at room temperature. Creation and decay rates of the hole trap have a 0.67 eV activation energy with a small (10(8) s(-1)) prefactor, suggesting that atomic motion plays a key role in the generation and quenching process.