Precipitation of silicon nanoclusters by laser direct-write

Abstract

The ability to use a laser to direct-write tracks of localized emission enhancement in PECVD-deposited Silicon rich oxide (SRO) films is demonstrated. For this purpose, 400 nm thick SRO films with varying excess Si content were irradiated with loosely focused 355 nm, 12 ps pulses at 80 MHz while being translated at 2mm/s. Mapping of areas irradiated with energies between 4.7 nJ and 5.5 nJ/pulse exhibits regions with the largest emission enhancement. Raman and photoluminescence (PL) measurements suggest precipitation of amorphous and crystalline Si nanoclusters. In the most emissive regions, the PL efficiency of the laser-annealed films was ~70% of that obtained by standard oven-annealing processes. Stress in Si crystals in some areas is identified as leading to quenching of the PL and is hypothesized to be caused by the densification of SRO matrix.