Inside Front Cover: Electronic Transport through Electron‐Doped Metal Phthalocyanine Materials (Adv. Mater. 3/2006)

Transport measurements for different electron‐doped metal–phthalocyanine (MPc) materials are reported by Morpurgo and co‐workers on p. 320. It is experimentally demonstrated that for these doped MPc materials, increasing the doping level results first in a metallic state and, subsequently, in the re‐entrance of an insulating state. The artist's impression on the inside cover shows an MPc film situated between two electrodes and exposed to a flux of alkali atoms in vacuum. The alkali atoms intercalate and donate electrons to the molecular material.     

Structural and electrical properties of amorphous GaAs sputtered at high substrate temperature (220 and 400 °C)

The influence of deposition conditions on structural and electrical properties of amorphous gallium arsenide (a-GaAs) thin films, deposited by RF sputtering at two substrate temperatures (glass substrates) and (Mo and ITO/glass substrates), is studied by both X-ray diffraction and electrical dark conductivity σ measurements, in the range (−150 °C to +150 °C) of temperature.The increase of sputtering argon pressure, P_Ar, leads to the growth of an amorphous structure and reduces the room-temperature dark conductivity, σ_RT, which suggests a reduction in the density of defects. Similar results are obtained with a decrease of the dc self-bias voltage, V_p, of RF electrodes. These results suggest that the density of defects is reduced with the energy decrease of the bombarding species while increasing P_Ar or decreasing V_p. The product of the target-to-substrate distance by the argon pressure, (d×P_Ar), representing the number of particles free path, confirms some results of the literature which indicate that the density of defects can be reduced significantly by reducing the energy of the bombarding species while increasing P_Ar or decreasing V_p. Materials of great resistivity (≈10⁸ Ω cm) are obtained either for low V_p or for great d×P_Ar. In addition, the thermal annealing reduces considerably the room-temperature dark conductivity.     

EFFECTIVE CONDUCTIVITY OF A DILUTE SUSPENSION AT MODERATE PARTICLE PECLET NUMBERS

The contribution of a shear field to the effective conductivity of a dilute suspension of small particles freely suspended in a viscous fluid is examined. The case of long cylindrical inclusion aligned parallel to the vorticity of a simple shear flow is calculated for particle Peclet numbers of O(1). The solution involves a combination of a domain perturbation and a numerical calculation for the far and the near fields, respectively. The resulting convective contribution to the bulk heat flux is compared with previous asymptotic analysis for Pe → ∞.     

POSITRON ANNIHILATION AND CONDUCTIVITY MEASUREMENTS ON POLYANILINE

The positron lifetime spectra and electrical conductivities have been measured for polyaniline as a function of protonation level ([H^ ] from 10^-7-10^0.8 mol/L)。We observed that (1) the short lifetime τ1,which was related to electron density in bulk,decreased with the protonation level;(2) the intermediate lifetime τ2≈360ps,almost remaining constant,whereas its intensity I2 increased with increasing protonation level which was related to the conductivity of meaterial.These results are discussed in terms of conducting island model.     

EXPERIMENTAL STUDIES OF CORRELATIONS BETWEEN GAS SENSOR RESPONSE AND SURFACE CHEMISTRY FOR SnO_2 (110)

In experimental study of the tin dioxide gas sensor, in situ sheet conductivity wasmeasured with ultrahigh vacuum four point resistivity probe. Surface composition and stoi-chiometry were detected using XPS. Four separate structure phases were obtained by LEED atdifferent annealing temperature, and emission was observed throughout the band gap up to theFermi level with UPS. Furthermore, effects of annealing temperature and dosed oxygen pressureon the surface reconstruction, O/Sn ratio, sheet conductivity, variation of the work function andband bending have been also investigated. The results help us to reveal the relationships betweenthe electronic and electrical properties of the material and its native defects structure. It is es-pecially useful to provide a more complete understanding of the basic operation mechanisms forsuch sensing materials.     

大地导电率的测定方法

详细介绍了四极法、“线—框”法、场强比测试法等大地导电率的测定方法,最后给出了计算实例。     

锂锰电池的现状和改进意见

综述了锂/二氧化锰电池的现状和改进意见,主要是提高锂/二氧化锰电池的高放性能。