Synthesis and photoluminescence of heavily La-doped α-Si3N4 nanowires via nitriding cyromilled nanocrystalline La-doped silicon powder

In this paper, the synthesis of heavily La-doped α-Si3N4 nanowires is firstly reported via nitriding the cryomilled La-doped nanocrystalline Si powder. The crystal structure, electronic structure and band structure of La-doped α-Si3N4 are calculated by using the CASTEP program code based on the first principles plane-wave pseudo-potential method. The microstructure and photoluminescence of heavily La-doped α-Si3N4 nanowires are investigated. The results suggest that La has been already incorporated into Si lattice after the cryomilling process and then successfully entered the lattice of α-Si3N4 with the nitridation process. The as-synthesized heavily La-doped α-Si3N4 nanowires show high purity and good crystallinity with 30-40 nm in diameter and several tens of micrometers in length. The optical property shows that there is an intense violet-blue visible emission from 350 nm to 450 nm with one peak at 388 nm due to the recombination between the valence band and the N4+ level at room temperature, which is in agreement with the calculated band structure of La-doped α-Si3N4.