The crystal structure, electrical, and magnetic properties of the Ni-based ternary compounds Y2NiGe3 and La2NiGe3 have been investigated. Powder X-ray diffraction patterns reveal that both compounds crystallize in the AlB2-derived hexagonal structure with values of the lattice parameters a = 4.066(7) angstrom and c = 4.025(1) angstrom for Y2NiGe3 and a = 4.180(2) angstrom and c = 4.334(1) angstrom for La2NiGe3. A sudden drop to zero value in the rho(T) curves and the diamagnetic behavior observed in the chi ac(T) curves conform the occurrence of bulk superconductivity in Y2NiGe3 and La2NiGe3 with T-C of 0.553 K and 0.394 K, respectively. Band structure calculations reveal that superconductivity in these two compounds is most probably from Y 4d electrons and La 5d electrons, respectively. (C) 2012 Elsevier B.V. All rights reserved.

The crystal structure, electrical, and magnetic properties of the Ni based ternary compounds R2NiGe3 (R = rare earth ions) have been investigated using powder X-ray diffraction, electrical resistivity, and magnetic susceptibility measurements. X-ray diffraction patterns reveal that all the samples studied crystallize in the AlB2-derived hexagonal structure with space P6/ mmm and the obtained values of the lattice constants a and c are a = 0.4188(1) nm and c = 0.4339(3) nm for La2NiGe3 and the lattice constants are found to decrease monotonically with increasing atomic number of R. A sudden drop to zero value in the rho(T) curve reveals that La2NiGe3 becomes superconducting with a midpoint transition temperature T-C of similar to 0.45 K. The chi(T) curves for all samples studied follow the Curie-Weiss behavior for T > 100 K, with the obtained value of effective moment mu(eff) close to the moment of the corresponding R3+ ions. The occurrence of peak in the chi(T) curve and a drop off in the rho(T) curve at the corresponding temperatures indicate that antiferromagnetic transition occurs below 10 K in Gd2NiGe3 and Dy2NiGe3. In addition, Pr2NiGe3 and Ho2NiGe3 also become magnetically ordered at low temperatures as inferred from the drop off in the rho(T) curve and the anomaly in the chi(T) curves in these compounds. The existence of minimun at 18 K followed by a-lnT dependence below 18 K in the rho(T) curve and a T-1/2 dependence in the chi(T) curve observed for Ce2NiGe3 reveal characteristic of a Kondo lattice in this compound.

The dark currents of InSb metal-insulator-semiconductor (MIS) charge injection devices (CIDs) in the temperature range 30 to 120K are studied. It is found that a thermal-generating process dominates the dark current in the high temperature region. When the device is under small bias voltage, a bump in the trap emission current appears below 70K. This current is due to carrier capture and emission processes of a hole trap state located in the bulk material, and the measured activation energy is 50meV. For larger bias conditions, the band-to-band tunnelling current gradually overcomes the trap emission current. It smears out the bump in the trap emission current, and shows a slightly temperature-dependent behaviour in the plot. The effects of field electrodes are also studied. It is found from experimental results that the edge of the electric field around the device periphery plays an important role in the band-to-band tunnelling process, and a field electrode with suitable bias can improve the dark current response drastically.