Satoshi Masuya

Synchrotron X-ray topography of dislocations in high-pressure high-temperature-grown single-crystal diamond with low dislocation density

Individual dislocations in high-pressure high-temperature-grown single-crystal diamond with a dislocation density of less than 47 cm−2 in the (001) growth sector were observed using synchrotron X-ray topography in the Laue geometry. By analyzing image contrasts for various g vectors using photoluminescence images, we found that dislocations in the (001) growth sector run in the [001] direction; some are pure edge dislocations having Burgers vectors (b) of a/2[110] or while others are mixed dislocations. Dislocations in the (111) growth sector have and run in the direction from [111] to [331]; they are classified as edge dislocations.

Determination of the type of stacking faults in single-crystal high-purity diamond with a low dislocation density of <50 cm−2 by synchrotron X-ray topography

The properties of stacking faults in a single-crystal high-purity diamond with a very low dislocation density of <50 cm?2 and a very low impurity concentration of <0.1 ppm were investigated by synchrotron X-ray topography. We found stacking faults on the {111} plane and determined the fault vector f of the stacking faults to be on the basis of the f g extinction criteria. Furthermore, we have found that the partial dislocations are of the Shockley type on the basis of the b g extinction criteria. Consequently, we concluded that the stacking faults are of the Shockley type and formed because of the decomposition of dislocations with into dislocations with and .

Observation of nanometer-sized crystalline grooves in as-grown β-Ga2O3 single crystals

On the surface of as-grown β-Ga2O3 single crystals that are cut and polished, we found nanometer-sized grooves elongated in the [001] direction. We confirmed that these grooves terminate within the crystals in the [010] direction. This proves that the grooves are different from micropipes penetrating crystals. Their typical length and width are 50–1200 nm in the [001] direction and ~40 nm in the [100] direction, respectively. The grooves tend to form an array in the [001] direction. The type of nanometer-sized grooves should be essentially different from etch pits.

Realization of direct bonding of single crystal diamond and Si substrates

Diamond/Si junctions have been achieved by surface activated bonding method without any chemical and heating treatments. Bonded interfaces were obtained that were free from voids and mechanical cracks. Observations by using transmission electron microscopy indicated that an amorphous layer with a thickness of ∼20 nm across the bonded interface was formed, and no structural defects were observed at the interface. The amorphous layer of the diamond side was confirmed to be the mixture of sp2 and sp3 carbons by electron energy loss spectroscopy analyzation. The sp3/(sp2 + sp3) ratio estimated from the X-ray photoemission spectra decreased from 53.8% to 27.5%, while the relative intensity of sp2 increased from 26.8% to 72.5% after the irradiation with Ar fast beam which should be predominantly attributable to the diamond-graphite conversion.

Diamond Schottky Barrier Diodes With NO 2 Exposed Surface and RF-DC Conversion Toward High Power Rectenna

A novel diamond Schottky barrier diode (SBD) with H-terminated surface exposed to NO2 gas is fabricated toward high power rectifying antenna (rectenna). The double NO2 exposures are introduced to provide high concentration of 2-D hole gas at the diamond surface. Experimentally, our SBDs have shown to give good rectifier properties with the high current density of 24 A/cm2 at a forward voltage of -2 V. A dual diode rectifier circuit using two diamond SBDs was designed with diode model constructed from experimental I-V curves. Values of circuit components such as dc block capacitance and load resistance were selected to achieve larger output voltage. Experimentally RF to dc conversion is demonstrated, where RF input voltage with 10 MHz and the amplitude of 9 V was converted into a dc output voltage as large as 4.2 V.