Ken Okano

Fabrication of a diamond field emitter array

A diamond field emitter array has been fabricated. by Chemical vapor deposition. Diamond was grown on an inverted pyramidal‐shape Si substrate followed by removal of the substrate. The fabricated array was placed in a high vacuum pumping system with the pressure of ∼10−7 Torr and the emission current as a function of the anode voltage was measured. The distance between the tungsten anode and the diamond surface was held constant at 100 μm throughout the measurement. As a result, a current larger than 10−4 A was obtained for an anode voltage of 6 kV. A linear relationship in the Fowler–Nordheim plot indicated the existence of electron field emission from the fabricated diamond field emitter array.

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.

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.

Doping of diamond

Abstract Semiconducting diamond films were deposited by the conventional hot filament chemical vapour deposition technique. Boron trioxide and diphosphorus pentaoxide have been used as the dopants for p- and n-type films respectively. The films obtained were identified as diamond by means of scanning electron microscopy, electron diffraction and Raman spectroscopy. The impurity concentrations in the films were evaluated using secondary ion mass spectroscopy. The semiconducting properties of the films were confirmed by measuring the resistivity, the Hall effect and the activation energy of the conductivity.

Fabrication of a miniature-size pyramidal-shape diamond field emitter array

A miniature-size pyramidal-shape diamond field emitter array has been fabricated using the mold technique. The tip radius of each pyramid was found to be less than 2000 /spl Aring/ from SEM observation and the fabricated array was identified as diamond from the results of AES and Raman spectroscopy. The array was placed in a high vacuum pumping system with the basic pressure of 10/sup -7/ Torr, and the emission property was measured using a Au ball anode with 100 /spl mu/m in diameter. The distance between the anode and the array was set up to 100 /spl mu/m throughout the measurements. As a result, the emission current of 1/spl times/10/sup -6/ A was observed at the applied voltage of 2400 V.

Characterization of semiconducting diamond film and its application to electronic devices

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 diamond films respectively. The films were identified as diamond from the results of the electron diffraction and Raman spectroscopy. The diode exhibited distinct rectification characteristics. The formation of the depletion layer was confirmed from the result of the electron-beam-induced current measurement.

Mold growth of polycrystalline pyramidal-shape diamond for field emitters

Abstract CVD diamonds were grown on inverted pyramidal-shape Si substrates, which were fabricated with standard photolithography and anisotropic etching techniques. After removing the substrates, pyramidal-shape polycrystalline diamonds with diamond seeds and without diamond seeds were obtained. The tip radius of each pyramid was estimated to be about 5000 A from scanning electron microscopy observations, and the pyramids were identified as polycrystalline diamond from the results of Auger electron spectroscopy, electron diffraction and Raman spectroscopy. When these pyramids were placed in a high vacuum system, relatively low-threshold electron emission was confirmed, suggesting that the pyramidal-shape polycrystalline diamonds fabricated with the mold technique would be appropriate for field emitters.

Isothermal capacitance transient spectroscopy measurements on polycrystalline diamond/hydrogenated amorphous silicon heterojunctions

A deep level in boron‐doped polycrystalline diamond films located approximately 0.6 eV above the valence‐band edge has been found using isothermal capacitance transient spectroscopy (ICTS) measurements. p‐n heterojunctions between polycrystalline diamond and hydrogenated amorphous silicon were used in the study. The density and the hole‐capture cross section of the deep level traps were determined from the temperature dependence of ICTS spectra and found to be 2×1016 cm−3 and 1×10−17 cm2, respectively.