Superconductivity and physical properties of Ba24Si100 determined from electric transport, specific-heat capacity, and magnetic susceptibility measurements

Both Ba24Si100 and Ba24Ge100 with crystallographically identical structure are found to be superconducting at 1.4 and 0.27 K, respectively. Physical properties of this superconductor Ba24Si100 are studied by electric transport, specific heat capacity, and magnetic susceptibility measurements. The density of states at the Fermi level NEF=0.148 states eV-1(Siatom)-1 and a distinct jump of Cp at the superconducting transition temperature ΔCp=0.272JK-1mol-1 are obtained. An exponential fit of Cp below the superconducting states gives an energy gap 2Δ=0.423meV and shows that this is a superconductor having s-wave character or isotropic energy gap. On the basis of our experimental data other important physical parameters are also derived

Calorimetric and Spectroscopic Studies of Water Adsorption onto Alkaline Earth Fluorides

Interactions between the surfaces of alkaline earth fluorides (CaF 2 , SrF 2 and BaF 2 ) and water molecules were investigated by calorimetric and spectroscopic methods. The exposed surfaces of the alkaline earth fluoride samples, with which the (100) crystalline plane is mainly associated, were found to be fully covered with strongly adsorbed water molecules, resulting in characteristic IR bands at 3684, 2561, 1947 and 1000 cm −1 , respectively. This surface was homogeneous towards further water adsorption. The strongly adsorbed water molecules were almost completely desorbed from the surface on evacuating the sample up to 473 K. The heat of immersion in water also increased with increasing pretreatment temperature; this may be attributed to surface rehydration of the alkaline earth fluorides. The state of the surface changed drastically as the pretreatment temperature was increased and stabilized towards incoming water molecules. Thus, the surface formed after evacuation at temperatures greater than 473 K was resistant to hydration even after immersion in water at room temperature. This surface was relatively heterogeneous towards water adsorption, although it behaved homogeneously towards argon adsorption. These facts indicate that strongly adsorbed water molecules appear to be somewhat specific towards the adsorption of further incoming water molecules. The adsorption properties of the (100) plane of alkaline earth fluorides towards water and argon molecules depend strongly on both the electrostatic field strength and the extent of rehydration of the alkaline earth fluoride surface

Equivalent ambipolar carrier injection of electrons and holes with Au electrodes in air-stable field effect transistors

Carrier injection from Au electrodes to organic thin-film active layers can be greatly improved for both electrons and holes by nano-structural surface control of organic semiconducting thin films using long-chain aliphatic molecules on a SiO2 gate insulator. In this paper, we demonstrate a stark contrast for a 2,5-bis(4-biphenylyl)bithiophene (BP2T) active emiconducting layer grown on a modified SiO2 dielectric gate insulator between two different modifications of tetratetracontane and poly(methyl methacrylate) thin films. Important evidence that the field effect transistor (FET)characteristics are ndependent of electrode metals with different work functions is given by the observation of a conversion of the metal-semiconductor contact from the Schottky limit to the Bardeen limit. An air-stable light emitting FET with an Au electrode is demonstrated