Quantum dots (QDs) are expected to be applied to emitting materials used in wide-color-gamut displays. However, the development of low-toxic alternatives is necessary because QDs that exhibit high color purity and highly efficient emission contain toxic materials such as Cd. In the present study, quantum dot light-emitting diodes (QD-LEDs) prepared using ZnInP/ZnSe/ZnS QDs as InP-based QDs were fabricated, and their electroluminescence (EL) properties were investigated. The synthesized QD dispersion showed a green photoluminescence (PL) spectrum with a peak wavelength of 509 nm, a full-width at half-maximum (FWHM) of 41 nm, and a PL quantum yield of 59.8%. Tris[2,4,6-trimethyl-3-(pyridin-3-yl)phenyl]borane (3TPYMB), which is an electron-transporting material (ETM), was added to the emitting layer (EML) of the QD-LEDs. The QDs and the ETM were nonuniformly deposited, the density of QDs in the EML was reduced, and the process of injecting electrons and holes into the QDs was changed. 3TPYMB assisted in recombination in the QDs because the electron injection barrier from 3TPYMB to the QDs was sufficiently small and because the deep highest occupied molecular orbital level effectively blocked holes. As a result, the external quantum efficiency was improved from 0.24% to 1.01%, and stable EL spectra with a peak wavelength of 522 nm and an FWHM of 46 nm, similar to the PL spectrum of the QD film, were obtained without being dependent on luminance. A bright and stable green EL emission was achieved with an InP-based QD-LED blended with 3TPYMB.

We propose a bit patterned media fabrication method based on low energy nitrogen ion implantation. Nitrogen ion implantation of fcc-Co/Pd multilayer or hcp-CoCrPt single layer suppresses their magnetizations at room temperature. Ion implantation reduces the Curie temperature from 600 to 400 K (or lower) as a result of lattice expansion and reduced exchange interaction between the magnetic atoms in the magnetic layer. We have made media with magnetic dots of 190 to 30 nm in diameter by nitrogen ion doping through resist patterns. Writing and reading of the signal from individual dots were performed with a commercial perpendicular magnetic recording head.

Group III-nitride nanocrystals are promising candidates for lighting applications. However, development of their colloidal quantum dots (QDs) has not progressed because of issues with the synthesis of indium nitride (InN) nanoparticles, such as the long reaction time and the generation of indium metal as a by-product. Here, we propose a new synthetic method that can solve almost all of the above problems and improve the quality of InN nanocrystals. In addition, we demonstrate that Ga-In-N QDs and Zn-In-N QDs synthesized using the proposed method exhibit photoluminescence.

The magnetism of a typical spinel ferromagnetic oxide, Fe3O4, was controlled via ion implantation. Nitrogen ions were accelerated at 6–10 kV and irradiated to the 13-nm-thick Fe3O4 thin films with dosages of 2 × 1016 to 6 × 1016 ions/cm2. The magnetization decreased with the increase in ion dosage, and there was almost no magnetization when 6 × 1016 ions/cm2 of nitrogen was irradiated, irrespective of the acceleration voltages. The results of the temperature dependence of the magnetization and the Mössbauer study suggest that the transition from ferromagnetic to nonmagnetic phases in the Fe3O4 thin film upon N2 ion irradiation proceeds abruptly without the formation of intermediate states.

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