High power density nuclear battery prototype based on diamond Schottky diodes

We report here for the first time a fabrication of betavoltaic battery prototype consisting of 200 single conversion cells based on Schottky barrier diamond diodes which have been vertically stacked with similar to 24% Ni-63 radioactive isotope. The maximum electrical output power of about 0.93 mu W was obtained in total volume of 5 x 5 x 3.5 mm(3). We used the ion-beam assisted lift-off technique to obtain conversion cells of minimal thickness comparable with the characteristic penetration length of beta-particles emitted by Ni-63 isotope. The obtained value of 15 mu m was limited by the mechanical strength of produced structures and process reliability. To check the performance of thin diamond based conversion cells we carried out IV-curves measurements at electron beam irradiation in SEM. We found that the sacrificial layer for the splitting of such thin conversion cell from HPHT diamond substrate did not cause a considerable degradation of device charge collection efficiency. As a result, the fabricated prototype provided the output power density of about 10 mu W/cm(3), that is the best known value for nuclear batteries based on Ni-63 radioisotope. Moreover, the long half-life of Ni-63 isotope gives the battery specific energy of about 3300 mWh/g that is an order of magnitude higher than the typical value of commercial chemical cells.