We designed, fabricated, and tested for the first time a prototype of nuclear micropower battery with an overall active area about 15 cm 2 consisted in 130 single cells based on Schottky barrier diamond diodes. Diodes selection for the battery assembly was performed on the basis of I-V curves measurements at electron beam irradiation in SEM. A typical energy conversion efficiency of each cell was about 4-6%. To characterize a battery prototype performance, we carried out photovoltaic measurements using different radioisotopes. Under irradiation by 63 Ni source with activity of 5 mCi cm À2 , the output power density of 3 nW cm À2 was obtained. Due to large energy loss of the emitted b particles in source itself, the total battery efficiency was only 0.6%. However, with the longlived 63 Ni isotope, this already gives the battery specific energy of about 120 W Á hr/kg, comparable with the commercial chemical cells. During experiments with high activity 90 Sr-90 Y source, no degradation was observed after 1,400 h of the radiation exposure. The maximum output power density of 2.4 mW cm À2 was achieved using 238 Pu a source. The results display that synthetic diamond is a highly promising material for nuclear microbattery fabrication. A strategy to further cell optimization is also discussed.

The yields of photonucleon reactions on the isotope 181 Ta that are induced by bremsstrahlung photons whose endpoint energy is 67.7 MeV are measured by the residual-activity method. The cross sections for photonucleon reactions on the isotope 181 Ta are calculated on the basis of the TALYS code and a combined model. The measured reaction yields are compared with their counterparts rescaled from cross sections obtained in experiments that employed beams of quasimonochromatic and bremsstrahlung photons. The spectra of neutrons emitted from 181 Ta nuclei after the absorption of photons having various energies are calculated within the TALYS code and the combined model in question.

No abstract

No abstract

The potential of ultrawide-bandgap (UWBG) semiconductors has not been fully explored because of the difficulty of forming a p-n homojunction. In this study, a mixed-dimensional UWBG p-n heterojunction composed of a p-type diamond substrate and an n-type exfoliated β-Ga2O3 nanolayer has been demonstrated via a van der Waals interaction; this type of structure does not suffer from lattice mismatch. Rectifying current-voltage characteristics with a rectification ratio exceeding 107 were obtained with a high reverse hard breakdown voltage of 135 V. This UWBG p-n heterojunction diode exhibited good thermal stability at elevated temperatures, retaining its high rectification ratio and low reverse leakage current. Excellent photoresponse characteristics, including responsivity (12 A W−1), rejection ratio (8.5 × 103), photo-to-dark-current ratio (3900), and fast response/decay characteristics, were observed from the diamond/β-Ga2O3 p-n heterojunction photodiode, showing no persistent photoconductivity. The mixed-dimensional p-n heterojunction diode based on two UWBG semiconductors (p-type diamond and n-type β-Ga2O3) can be used as a robust building block in next-generation power electronics and solar-blind optoelectronics.