Thin film and bulk fabrication of room-temperature-stable electride C12A7:e− utilizing reduced amorphous 12CaO · 7Al2O3(C12A7)

Heavily electron-doped 12CaO · 7Al2O3(C12A7) exhibits unique electronic properties such as high electronic conductivity of 1500 S cm−1 (to superconductor via metal–insulator transition) and a very small work function (2.4 eV) arising from electrons entrapped in sub-nanometer-sized cages inherent to the crystal structure. We report the efficient synthetic processes of bulk and thin film C12A7:e− using the reduced C12A7 melt or a-C12A7. Solidification of the melt produced in carbon crucibles and crystallization of the reduced C12A7 glass (insulating) in vacuum yielded bulk C12A7:e−. It was suggested that C 2 2 - ions work as a template to form the nano-cages in the crystallization processes. The films of C12A7:e− were fabricated by the reduction treatment of crystalline C12A7 thin films with reduced a-C12A7. By applying this process, heavily electron-doped thin films of 12SrO · 7Al2O3 with the same crystal structure as C12A7 but a non-equilibrium phase was first realized.