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  • Author: S. Hosokawa x
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Abstract

Voltage-current (V-I) characteristics of nitrogen glow discharges at 10 torr gas pressure were obtained in a wide discharge current range from 10 mA to 250 A using parallel-plane electrodes. A low inductance capacitor of 1.89 μF and a discharge apparatus with co-axial configuration were used to produce a nitrogen glow discharge with high current. The time-dependent glow voltage was obtained accurately by solving the circuit equation using the measured values of the current and breakdown voltage. Damping resistor was employed to control the glow discharge current and was altered from 0.6 to 225 Ω in order to obtain the V-I characteristics in a wide current range. The glow discharge voltage was almost constant until the whole surface of the cathode was covered with glow, i.e., until the discharge current became 3.0 A under our experimental condition. The voltage, however, increased with the current when the glow covered over the cathode. Electron density and temperature in a positive column of the glow discharge at 250 A discharge current were obtained to 7.4×1011 cm-3 and 3.6 eV from calculation based on nitrogen swarm data. Number densities of ions, metastable molecules and atomic radical particles were predicted based on chemical analysis using measured voltage-current characteristics. The metastable molecule N2 (A 3Σ+ u) density at 250 A discharge current was calculated to 1.8×1013 cm-3, which was one-order higher value than that of electron.

Anomalous x-ray scattering experiments on glassy GexSe1−x have been carried out at energies close to the Ge and Se K edges at concentrations close to the onset- and at the mid-point of the rigidity percolation threshold (x = 0.195 and 0.23). The total structure factors S(Q) show rapid variations in both the position and intensity of the prepeak around 11 nm−1, while it stays almost unchanged in the remaining Q range. The differential structure factors Δi S(Q) comprise characteristic features. Comparing them suggests that the prepeak purely originates from the Ge-Ge correlation. The present structural results strongly support the chemically-ordered continuous-random-network model for the Ge-Se glasses. The origin of the prepeak was discussed from a comparison between the S GeGe(Q) of g-GeSe2 obtained by Petri et al. and S(Q) of a-Ge. The concentration dependence of the prepeak is consistent with the Raman data, which reveal the diminishing of short Se chain connections between the Ge(Se1/2)4 tetrahedra near the stiffness transition composition.