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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 insufficient data on a structure of the boron-doped diamond (BDD) has frustrated efforts to fully understand the fascinating electronic properties of this material and how they evolve with doping. We have employed X-ray diffraction and Raman scattering for detailed study of the large-sized BDD single crystals. We demonstrate a formation of boron-carbon (B-C) nanosheets and bilayers in BDD with increasing boron concentration. An incorporation of two boron atoms in the diamond unit cell plays a key role for the B-C nanosheets and bilayer formation. Evidence for these B-C bilayers which are parallel to {111} planes is provided by the observation of high-order, super-lattice reflections in X-ray diffraction and Laue patterns. B-C nanosheets and bilayers minimize the strain energy and affect the electronic structure of BDD. A new shallow acceptor level associated with B-C nanosheets at ~37 meV and the spin-orbit splitting of the valence band of ~6 meV are observed in electronic Raman scattering. We identified that the superconducting transitions occur in the (111) BDD surfaces only. We believe that the origin of Mott and superconducting transitions is associated with the two-dimensional (2D) misfit layer structure of BDD. A model for the BDD crystal structure, based on X-ray and Raman data, is proposed and confirmed by density functional theoretical calculation.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-1215-6) contains supplementary material, which is available to authorized users.

All-diamond optical assemblies holding state-of-the-art type IIa diamond crystals enable the construction of a beam-multiplexing X-ray double-crystal monochromator for hard X-ray free-electron lasers. Details on the design, fabrication and X-ray diffraction characterization of the assemblies are reported.

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