Ichimin Shirotani

Growth of Large Single Crystals of Black Phosphorus at High Pressures and Temperatures, and its Electrical Properties

Abstract The crystal growth of black phosphorus(B.P.) and its electrical properties have been studied at high pressures and high temperatures. A wedge type cubic anvil high pressure apparatus was used in the present experiments. From the measurement of the electrical resistance the melting points of B.P. have determined at high pressures. When B.P. is melted in the carbon furnace and slowly cools at 2.3 GPa, the large single crystals have often been grown. The size of the largest one is 4 mm in diameter and 5 mm in length. The anisotropic resistivity within the layers(ac-plane) has been observed. The resistivities along the a-, c- and b(perpendicular to the layer)-axes were about 0.1, ∼1 and 102∼103 Ωcm, respectively at atmospheric pressure. The resistivity along the a-axis was insensitive to pressure; on the other hand, the resistivities along the c- and b- axes decreased rapidly with increasing pressure at room temperature. The resistivity along the b-axis was about two orders of magnitudes larger than ...

Effect of Pressure on the Absorption Spectra of Oriented and Amorphous Organic Films

Abstract The absorption spectra of oriented and amorphous naphthacene and pentacene film have been measured at high pressure. The Davydov splitting of 0–0 band in oriented films increase with increasing pressure at the rate of 37 cm−1/kbar for naphthacene and 70 cm−1/kbar for pentacene. The 0–2 vibronic bands of both oriented films show the large red shifts compared with the 0–1 vibronic band. For amorphous films the Davydov splitting is not observed at atmospheric pressure. The pressure induced spectral red shifts in the amorphous state are slightly larger than those in the crystalline-state.

Polarization energies of tetrathiafulvalene derivatives

Abstract Ultraviolet photoelectron spectroscopic studies were carried out on dimethyl-, tetramethyl- and dibenzo-derivatives of tetrathiafulvalene in the gaseous and solid state. As the difference between the threshold ionization potentials in both states, we obtained the polarization energies of those compounds in the solid state. Dibenzotetrathiafulvalene (DBTTF) showed the differential relaxation shifts due to the different electronic bands. Polarization energies of the two methyl-derivatives are very small, 0.9 and 1.1 eV. While that of DBTTF is the largest, 2.3 eV, among the donor-like compounds measured, due to the large molecular polarizability. Comparing these values with the polarization energies of related compounds, it is suggested that the DBTTF form very stable charge-transfer complexes with some appropriate acceptor molecules

Conductive tetraselenonaphthacene and iodanil under very high pressure

Abstract Tetraselenonaphthacene and iodanil become highly conductive at pressures above 400 kilobars. The lowest electrical resistivity is 1 × 10 −1 ohm cm in the former and 5 × 10 −2 ohm cm in the latter, respectively. In the curve showing the change in resistance with increasing pressure for tetraselenonaphthacene there appears a broad and shallow minimum at pressures between 300 and 500 kilobars.

Electrical conductivity, photoemission and absorption spectrum of tetraselenonaphthacene, C18H8Se4

Abstract The electrical conductivity, the photoemission and the absorption spectrum of tetraselenonaphthacene (TSN) evaporated film were studied. The conductivity of TSN film in a vacuum of 1.6 × 10−8 torr was 7.7 × 10−7 Ω−1 cm−1. When the film was exposed to air at atmospheric pressure, the value of the conductivity was found to be 1.1 × 10−4 Ω−1 cm−1. The ionization potential of the film estimated from its electron spectroscopy energy distribution curve was 4.45 eV. The absorption band at 15 400 cm−1 was insensitive to the pressure; on the contrary the band at 11 900 cm−1 showed a large red-shift at the rate of 120 cm−1/kbar. The remarkable difference in the pressure shift of the absorption bands in TSN film may arise from the Davydov splitting.

Electrical conductivity of hexaiodobenzene and tetrahalo-p-benzoquinone under very high pressures

Abstract The electrical resistances of hexaiodobenzene, iodanil, bromanil, and chloranil have been studied under very high pressures. The lowest resistivity at 500 kbar is about 5 Ω-cm for hexaiodobenzene and 5 × 10−2 Ω-cm for iodanil. This difference may be mainly explained by the charge transfer from iodine to oxygen atoms in the latter compound.

Anomalous Fluorescence of Pure Anthracene Crystal under High Pressure

Abstract The effect of pressure on the fluorescence spectra of a few aromatic hydrocarbons was reported recently.1 In this report, we present an anomalous fluorescence of anthracene crystals which may be ascribed to a formation of resonance dimers under high pressure.

Physicochemical properties of alkali metal cation-TCNQ anion radical salts

Abstract Simple alkali metal cation-TCNQ anion radical salts are classified in two groups from the differences in their physicochemical properties and crystal structures. Li-, Na-, K-, and Rb(I)-TCNQ are comprised in Group A. Li-TCNQ exhibits distinct behavior from other salts in Group A. Rb(II)- and Cs-TCNQ belong to Group B. Phase transitions, electrical conductivities, and absorption spectra in these simple salts are closely related to their crystal structures.

Photoemission from silver subfluoride, Ag2F

Abstract Ag 2 F was made by the electrolysis of aqueous silver fluoride solutions. The work function of this metallic compound was estimated from the threshold value of photoelectric emission, 5.5 4 eV, and also from the photoelectron spectroscopical method, 5.4 9 eV.

Absorption and fluorescence spectra of benzo-[g, h, i,]-perylene, C22H12

Abstract Benzo-[ g, h, i ]-perylene of a commercially available grade contained a small amount of perylene, about 10 −3 mole/mole, as impurity even after careful purification, caused by the similarity of their physical properties. The concentration of perylene,in benzo-[ g, h, i ]-perylene was decreased to less than 10 −6 mole/mole through a newly developed purification method. The absorption spectra of the pure sample in benzene solution had no weak band at 436 mμ (2.29 × 10 4 cm −1 ), which was assigned to perylene. The fluorescence spectrum of solid benzo-[ g, h, i ]-perylene, a broad weak band with a maximum at 470 mμ (2.13 × 10 4 cm −1 ), was very different from that of the impure hydrocarbon. The fluorescence spectra of solid film at low temperature were very intense and had vibrational structures.