Yusuke Kume

Fabrication of ZnTe Light-Emitting Diodes Using Bridgman-Grown Substrates.

We have succeeded in fabricating ZnTe light-emitting diodes (LEDs) using p-ZnTe substrate grown by the vertical Bridgman method. The substrate showed a full width at half maximum of the X-ray rocking curve of about 90 arcsec, and strong near-band-edge emission in the photoluminescence spectrum at low temperatures. pn-junction LED was fabricated by an Al diffusion technique. From the I-V curve, the turn-on voltage was found to be approximately 2 V. Pure-green electroluminescence was observed clearly at a wavelength of 550 nm at room temperature.

Structural Properties of ZnTe Epilayers Grown on (0001) α-Al2O3 Substrates by Metalorganic Vapor Phase Epitaxy

ZnTe layers have been grown on (0001) sapphire (α-Al2O3) substrates by metalorganic vapor phase epitaxy using dimethylzinc and diethyltelluride as the source materials. The structural properties of the ZnTe layers are investigated by X-ray diffraction and reflection high-energy electron diffraction analyses. It is revealed that (111) ZnTe single-crystalline layers can be obtained on (0001) α-Al2O3 substrates at a substrate temperature above 410 °C. The X-ray rocking curve measurements confirm that the crystalline quality of the ZnTe layers depends strongly on the substrate temperature, and the best crystalline quality ZnTe layer is obtained at a substrate temperature of 430 °C.

Strong Room-Temperature UV Luminescence from ZnO Grown by Metal Organic Decomposition

ZnO films were fabricated on glass substrates by metal organic decomposition (MOD). X-ray diffraction, reflection high-energy electron diffraction, and energy-dispersive X-ray spectroscopy revealed that the obtained ZnO films are stoichiometric polycrystalline with a wurtzite structure. Strong near-band-edge emission in the UV region without any deep-level emissions was observed from the ZnO films at room temperature. The results show that MOD is a promising growth method for obtaining high-quality ZnO films, which paves the way for the fabrication of electronic and optoelectronic devices using ZnO at low cost.

Synchrotron Radiation‐Excited Etching of ZnTe

Synchrotron radiation‐excited etching of compound semiconductor, ZnTe, was investigated using the SF6 and Ar gases. In the case of SF6 gas, the ZnTe was not etched but thin film of a fluorine containing material, e.g. ZnF2, was deposited on the surface of ZnTe. On the other hand, ZnTe was etched by using Ar gas under the negative sample bias to the sample. The etched pattern obtained by placing a Ni mesh showed that only the irradiated area was etched. The etching rate was estimated to be around 4.5×10−2 A/mA⋅min.

Growth Properties of Poly(tetrafluoroethylene) Films by Synchrotron Radiation Ablation

High-quality poly(tetrafluoroethylene) (PTFE) films have been grown on Si substrates by synchrotron radiation ablation of a PTFE target. Only doublet absorption structures assigned to C–F asymmetric and symmetric stretching vibrations in CF2 groups are observed, suggesting that the CF2 groups in the grown PTFE film are organized in an ordered manner through linear attachment. The growth rate of the PTFE films increases with increasing target temperature, while it decreases with increasing substrate temperature. It has been shown that the thickness of the PTFE film with a high-spatial-resolution structure can be easily controlled at nanometer order by changing the synchrotron radiation irradiation dose.