Terutaro Nakamura

Synthesis of n-type semiconducting diamond film using diphosphorus pentaoxide as the doping source

An n-type semiconducting diamond film has been synthesized by the hot filament CVD method using diphosphorus pentaoxide as the doping source. The obtained film was identified as polycrystalline diamond containing few sp2 components by means of several methods including Raman spectroscopy. From measurements of the Hall effect and the Seebeck effect, the film was found to be an n-type semiconductor.

Tourmaline group crystals reaction with water

Abstract The pyroelectricity in tourmaline crystals has proved to be the secondary pyroelectric effect due to the thermal expansion and the piezoelectricity. On the c-face of a tourmaline powder of radius a [μm], there exists the electric field of 107 [V/m] which decreases following (a/r)3 at distance r and is faint at teen [μm] value of r. Several attributes of water that has contacted tourmalines undergo definite changes. Quite a few novel applications of tourmalines are possible.

Synthesis of B-doped diamond film

Abstract Boron-doped diamond films have been synthesized by the thermal filament CVD method. As the doping source, boron trioxide powder was used instead of diborane. The films obtained were identified as diamond by several methods including Raman spectroscopy. The resistivity of the films was inversely proportional to the doping concentration over four order. p-Type electrical conduction was also confirmed by measuring the Seebeck effect.

p‐n junction diode made of semiconducting diamond films

A diamond p‐n junction diode fabricated by the chemical vapor deposition technique, shows distinct rectification characteristics. From the electron beam induced current measurement, the existence of a depletion region or a space‐charge region around the interface between the n‐ and p‐type semiconducting diamond layers was identified.

Fabrication of a diamond p-n junction diode using the chemical vapour deposition technique☆

Abstract A diamond p − n junction diode has been fabricated by the chemical vapour deposition technique. Diphosphorus pentaoxide and boron trioxide were used for the doping sources for the n - and p -type layers, respectively. The diode shows distinct rectification characteristics at 300 K room temperature. This diode shows rectification even at 370 K and this result implies the possible use of diamond as a semiconductor in high temperature conditions.

Soft phonon in BaTiO3

Abstract It is of course my greatest honor and pleasure that the international journal “Ferroelectrics” has published the “Nakamura Special Issue” on “Structural Phase Transitions in Ferroelectronics and their Related Materials.” celebrating my sixty ninth birthday. Taking advantage of this opportunity, I will summarize my research on the soft phonon in BaTiO3, because every part of the report of this subject has been published separately in quite a few different journals, each time a new finding has been achieved. The author greatly appreciates Dr. George Taylor, the Editor, Prof. W. Kinase and other international guest editors for providing me with this opportunity.

Dielectric Dispersion of Rb1-x(NH4)xH2PO4

The frequency dispersion of the dielectric constants of mixed crystals of Rb1-x(NH4)xH2PO4 was investigated over the full range of the concentration. For 0.25≤x≤0.8, a remarkable frequency-dispersion was found, which supports the existence of a glasslike phase. For 0≤x≤0.2, two kinds of dispersions, which are distinct from those observed for 0.25≤x≤0.8, were found.

Damping constants of optical phonons in tetragonal BaTiO3

Abstract We investigate the Raman scattering of a tetragonal BaTiO3 single crystal and report a study of wavevector dependence of the damping constant in the E(x)TO modes, which are obtained by varying the geometric configuration of the sample. We also discuss the damping constant of oblique phonons on the basis of Mertens formula.

Birefringence anomaly induced by thermal gradient along the c-axis in LiNbO3

LiNbO3 crystal becomes biaxial when a thermal gradient exists along the c-axis of the crystal. This new effect-was observed by the conoscopic change of a c-plane sample and was confirmed by the measurement of birefringence An along the c-axis. The optical anomaly was more remarkable at higher temperature above 70°C. The magnitude of An induced by the thermal gradient ΔT was 10-4 at ΔT = 20°C/mm.

Diffuse phase transition and low temperature dielectric constant in PbTiO3

Abstract The dielectric constant minimum in the sub-Kelvin temperature region has been found both for amorphous and crystalline PbTiO3. The glass-like behavior gradually vanishes as the transition changes from the diffuse to the sharp transition.