Showing papers by "University of Electro-Communications published in 1974"

Effect of Oxygen on Electrical Properties of Lead Phthalocyanine

Abstract: Oxygen molecules were found to enter into lead phthalocyanine single crystals by thermal diffusion when they were annealed in an oxygen gas of atmospheric pressure above 230°C for more than ten hours. Diffusion constant is 7.2 ×10 -9 cm 2 sec -1 at 242°C with activation energy of 1.4 eV. Dark conductivity σ increased by three orders of magnitude at room temperature with the heat treatment. Correspondingly, activation energy of conductivity E defined by σ∝exp (- E / k T ) decreased from 0.85 to 0.54 eV. The measurement of thermoelectric power indicates that positively charge carriers are generated in the presence of oxygen. The experimental results are explained on the model that an oxygen molecule acts as a center of carrier generation by accepting an electron from a neighboring lead phthalocyanine molecule and releasing the hole-like carrier.

Measurement of the Elastic Compliance Constants of Antiferroelectric Copper Formate Single Crystals

Abstract: The temperature dependence of the components of the elastic compliance constants of copper formate tetrahydrate crystals, s 11 , s 22 , s 33 , s 15 , s 35 , ( s 44 +2 s 23 ), ( s 55 +2 s 13 ), and ( s 66 +2 s 12 ), have been measured at 100 kHz by the composite bar method. ( s 44 +2 s 23 ) and ( s 66 +2 s 12 ) have been found to show sharp and high peaks at the antiferroelectric phase transition temperature T 0 . All absolute values of s 's show stepwise decreases when the crystal enters the antiferroelectric phase.

Studies of a New ESR Center in X-Irradiated CaF 2 Crystals

Abstract: Electron spin resonance studies have been carried out on x-irradiated CaF 2 single crystals. A new ESR center is induced with x-irradiation at room temperature. This new ESR center exhibits well resolved super hyperfine structures. The ESR spectrum is analysed with a spin Hamiltonian \(\mathscr{H}{=}g\beta\textbf{H}\cdot\textbf{S}+\sum_{i{=}1}^{8}\textbf{S}\cdot\textbf{a}_{i}\cdot\textbf{I}_{i},\quad\text{with}\quad S{=}1/2\quad\text{and}\quad\textbf{I}_{i}{=}1/2\). The obtained spin Hamiltonian parameters are g =2.0007, | a s |=10.6 and | a p |=1.8 gauss. The ESR center grows larger with x-irradiation time and its growth is saturated after irradiation of about 4 to 5 hours. The thermal decays of the ESR center are well approximated with the first order kinetics, and its activation energy is determined as E =0.47±0.05 eV. The optical bleachings of the ESR center were also made in the range from 398 to 658 nm, and ESR signals were reduced most prominently at 580 nm.

Photocurrent and spectral characteristics of field-induced junctions

Abstract: The photocurrent of a p -channel gate-controlled MOS diode, which is induced within a field-induced junction ( FI junction) and flows into drain circuits through an inversion layer, was measured. The lateral potential drop in the channel gives rise to narrowing of the depletion layer, so that the photocurrent begins to saturate for a small gate voltage or strong illumination. The spectral dependence of the photocurrent shows that the photosensitivity of the FI junction is superior to that of a PN junction in the short wavelength region because incident light can be introduced directly into the depletion layer of the FI junction. Electron excitations related to interface states are also observed in the spectral photoresponses of the samples prepared by the wet oxidation and the level is found at 0·11 eV above the valence band.

Dual‐basis orthonormality‐constrained variation method

Abstract: The method of orthonormality-constrained variation is extended using a dual-basis set instead of a single orthonormal basis. The complete and the partial variation methods are discussed and applied to electronic systems. It is found that the present formulation leads to the most general equation in the coupling operator method.

ESR Study of SnO 2 Doped with Nickel Ions

Abstract: ESR investigations of nickel ions in SnO 2 crystals were carried out at liquid helium temperature, whose angular dependence could be analysed by a spin Hamiltonian \(\mathscr{H}{=}\beta\textbf{\itshape H}{\cdot}\textbf{\itshape g}{\cdot}\textbf{\itshape S}_{\text{e}}{+}\sum\limits_{i}\textbf{\itshape S}_{\text{e}}{\cdot}\textbf{\itshape a}_{i}{\cdot}\textbf{\itshape I}_{i}\), with S e =1/2 and I i =1/2. The spin Hamiltonian parameters were determined as g z =2.18±0.02, g x =4.78±0.3, g y =6.12±0.4; | a z |=7.9±0.4, | a x |=7±1 and | a y |=5.9±0.3 gauss, respectively, which were interpreted as Ni 3+ ions in the intermediate crystal field.

Correlation between Zero-Crossing Intervals of Gaussian Processes

Abstract: The slowly-decaying and alternating behavior of the correlation coefficient between lengths of the zero-crossing intervals of a Gaussian process, which was reported by one of the authors, is studied in detail by changing the magnitude of the low-frequency component of the Gaussian process having a relatively broad-band spectrum. Depending on the magnitude of the low-frequency component, the sign of the correlation coefficient becomes either negative or positive. Also, the value of the correlation coefficient for the narrow-band process can be altered by adding the low-frequency component to the narrow-band process. These results confirm the validity of the simple model proposed previously.