Luminescence from Si nanocrystals in silica deposited by helicon activated reactive evaporation

An alternative method is investigated for the preparation of Si-rich SiO₂ films used for the fabrication of light-emitting Si nanocrystal structures. The technique, helicon-activated reactive evaporation (HARE), combines e-beam evaporation of silicon with plasma activation of a reactive argon-oxygen atmosphere, and has the advantage of being able to produce thick, H-free films suitable for planar photonic device applications. The nanocrystal-rich films were formed by annealing as-deposited films at 1100°C for 1 h. Room temperature photoluminescence was then measured and compared with that from ion-implanted samples annealed under similar conditions. The HARE-deposited films exhibited strong visible luminescence for a range of excess Si concentrations, demonstrating their potential for the manufacture of such materials. The films also exhibited a concentration dependence comparable to that of ion-implanted samples: the luminescence intensity initially increased with excess Si concentration up to a maximum before decreasing with increasing concentration thereafter. The cause of the decrease at higher concentrations is briefly discussed.