Abstract
CO 2 laser annealing induced effects of dehydrogenation, Si nanocrystal precipitation, ablation, and optical refinement in PECVD grown SiO 1.25 film are investigated. Dehydrogenation shrinks SiO 1.25 thickness by 40 nm after annealing at laser intensity (P laser ) of 4 kW/cm 2 for 1.4 ms. As P laser increases to 6 kW/cm 2 , the photoluminescence (PL) red-shifts to 806 nm due to the size enlargement of Si nanocrystals, while a reduced optical bandgap energy from 3.3 to 2.43 eV and an enlarged refractive index from 1.57 to 1.87 are also observed. Transmission electron microscopy analysis reveals that the randomly oriented Si nanocrystals exhibit an average diameter of 5.3 nm and a volume density of 1.9 × 10 18 cm -3 . CO 2 Laser ablation initiates at intensity higher than 7 kW/cm 2 , which introduces numerous structural defects with a strong PL at 410 nm. Such an ablation inevitably leads to a blue-shifted optical bandgap energy from 2.43 to 2.76 eV as P laser enlarges from 6 to 12 kW/cm 2 are concluded. Copyright © 2006 American Scientific Publishers All rights reserved.