Photoluminescence properties of Nd-doped silicon oxide thin films containing silicon nanoparticles

Neodymium-doped silicon-rich silicon oxide thin films SiOx:Nd (1≤x≤2) were deposited by thermal co-evaporation of SiO and SiO2 and annealed at temperatures up to 1200 °C. Due to the phase separation process induced by annealing treatments, amorphous silicon nanoparticles (aSi-np) are obtained. For annealing temperatures equal to or above 1000 °C, silicon nanocrystals (Si-nc) embedded in a SiO2 matrix are obtained. Photoluminescence (PL) properties of the SiOx:Nd thin films were studied as a function of the silicon excess, the annealing temperature and the Nd content. For annealed samples, Nd-related PL peaks at 920 nm, 1100 nm and 1400 nm are observed. It is shown that, despite the efficient energy transfer between Si-nc and Nd3+ ions, the highest luminescence intensity is obtained for samples containing aSi-np. Moreover, the concentration quenching effect occurs for higher concentration values in samples containing aSi-np, compared to that containing Si-nc. These results show that Si-nc are not necessary to indirectly excite Nd3+ ions and that samples annealed at temperatures lower than 800 °C are of potential interest for applications because of a lower thermal budget compared to that required for samples containing Si-nc.