We successfully observed electron emission from hydrogenated diamond (111) p+-i-n+ junction diodes. Here, p+- and n+-layers mean that the boron and phosphorous impurity concentrations in these layers are around 1020 cm-3. Then the p+-layer on top of the diode suppresses electron emission from the top-surface area. The heavily doped layers also play an important role to obtain high diode and emission currents. The emission started when the applying bias voltage was equal to the built-in potential, and the emission current reached to over 1 μA at room temperature operation. With taking into account our previous photoemission yield spectroscopy results and with the very high binding energy of free excitons of 80 meV in diamond, we suggested that the electron emission was derived from free excitons generated in the i-layer of the diodes.

The efficiency and speed with which first responders, paramedics, and emergency physicians respond to an event caused by the release of a chemical is an important concern in all modern cities worldwide. A system for the initial triage and decontamination of victims of a chemical release was developed using colored clothes pegs of the following seven colors: red, yellow, green, black, white, and blue. Red indicates the need for emergency care, yellow for semi-emergency care, green for non-emergency care, black for expectant, white for dry decontamination, and blue for wet decontamination. The system can be employed as one of the techniques directed at improving the efficiency of decontamination in countries where there is a risk of chemical releases. It is recommended that this system should be adopted internationally and used for both drills and actual events.

Phosphorus doping on (001)-oriented diamond is introduced and compared with results achieved on (111) diamond. Detailed procedures, conditions, doping characteristics, and recent electrical properties of (001) phosphorus-doped diamond films are described. Now the highest mobility is reached to be ∼780 cm2/Vs at room temperature. The carrier compensation ratio, which is still high around 50-80 %, is the most important issues for (001) phosphorus-doped diamond to improve its electrical property. The origin of compensators in phosphorus-doped diamond is investigated, while yet to be identified.

Ultraviolet light emitting diode with p-i-n junction structure is also introduced using (001) n-type diamond. A strong UV light emission at around ∼240 nm is observed even at room temperature. High performance of diamond UV-LED is demonstrated.

We have observed visible photoluminescence (PL) spectra (peak energy: 3.1 eV) of size-controlled silicon (Si) nanoparticles annealed in oxygen gas. The PL peak energy did not depend on the temperature, and the PL lifetime was relatively fast (on the order of nanoseconds). It was inferred that the visible PL was attributed to localized states in the oxidized surfaces of size-controlled Si nanoparticles. We also observed the PL excitation spectra and studied the excitation process. In order to elucidate mechanisms of the visible PL, excitation and recombination processes are discussed.

We have developed silicon (Si) nanocrystallite light-emitting devices synthesized by a novel integrated process in which a size-controlling unit of differential mobility analyzer (DMA) is combined to a nanocrystallite formation unit of pulsed laser ablation (PLA). The size-controlled Si nanocrystallites as active layers have been deposited on Si substrates, and have been covered with stoichiometric indium oxide (In2O3) thin films synthesized also by the PLA process. The electroluminescence (EL) spectra had a narrow bandwidth of 0.15 eV peaked at slightly higher energy region (1.17 eV) than the bulk Si energy gap (1.10 eV), at room temperature.