Measurement and comparison of individual external doses of high-school students living in Japan, France, Poland and Belarus-the 'D-shuttle' project.

Twelve high schools in Japan (of which six are in Fukushima Prefecture), four in France, eight in Poland and two in Belarus cooperated in the measurement and comparison of individual external doses in 2014. In total 216 high-school students and teachers participated in the study. Each participant wore an electronic personal dosimeter 'D-shuttle' for two weeks, and kept a journal of his/her whereabouts and activities. The distributions of annual external doses estimated for each region overlap with each other, demonstrating that the personal external individual doses in locations where residence is currently allowed in Fukushima Prefecture and in Belarus are well within the range of estimated annual doses due to the terrestrial background radiation level of other regions/countries.

Deep level transient spectroscopy of hole traps related to CdTe self-assembled quantum dots embedded in ZnTe matrix.

The capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements have been made on a Schottky Ti-ZnTe (p-type) diode containing CdTe self-assembled quantum dots (QD) and control diode without dots. The C-V curve of the QD diode exhibits a characteristic step associated with the QD states whereas the reference diode shows ordinary bulk behavior. A quasistatic model based on the self-consistent solution of the Poisson's equation is used to simulate the capacitance. By comparison of the calculated C-V curve with the experimental one, hole binding energy at the QD states is found to be equal about 0.12 eV. The results of DLTS measurements for the sample containing QDs reveal the presence of a low-temperature peak which is not observed for the control diode. Analysis of its behavior at different bias conditions leads to the conclusion that this peak may be related to the hole emission from the QD states to the ZnTe valence band. Its thermal activation energy obtained from related Arrhenius plot equals to 0.12 eV in accordance with the energy obtained from the Poisson's equation. Thus based on the C-V and DLTS studies it may be concluded that the thermal activation energy of holes from the QD states to the ZnTe valence band in the CdTe/ZnTe QD system is equal about 0.12 eV.

E center in silicon has a donor level in the band gap.

It has been an accepted fact for more than 40 years that the E center in Si (the group-V impurity--vacancy pair)--one of the most studied defects in semiconductors--has only one energy level in the band gap: namely, the acceptor level at about 0.45 eV below the conduction band. We now demonstrate that it has a second level, situated in the lower half of the band gap at 0.27 eV above the valence band. The existence of this level, having a donor character, is disclosed by a combination of different transient-capacitance techniques and electronic-structure calculations. The finding seriously questions some diffusion-modeling approaches performed in the past.