It was demonstrated that a focused CO2 laser beam (10.6µm) could be used for the local synthesis of light-emitting defects and Si nanoparticles in Si-rich oxynitride thin films. Films with a stoichiometry of SiO1.08N0.32 were prepared by plasma-enhanced chemical vapor deposition with N2O and SiH4. Strongly absorbing CO2 laser light was then used to induce local heating in the films in air ambient using power densities of 0 to 580W/cm2 and times of 5s to 1h. High-resolution cross-sectional transmission electron microscopic images of the irradiated region revealed the presence of crystalline Si nanoparticles. Photoluminescence spectra taken from irradiated areas revealed 2 distinct peaks around 570 and 800nm. Using a combined transmission electron microscopy, Rutherford back-scattering, forming-gas annealing, photoluminescence and photoluminescence lifetime study, it was concluded that the 570nm peak - with a short photoluminescence lifetime (<10ns) - was related to defects that were characteristic of Si sub-oxides and that the 800nm peak was due to exciton recombination within the Si nanoparticles. The appearance of an isosbestic point in the photoluminescence spectra suggested that, upon CO2 laser heating, Si nanoparticles were formed at the expense of the luminescent defect structures; which annealed out.

Controlling Defect and Si Nanoparticle Luminescence from Silicon Oxynitride Films with CO2 Laser Annealing. A.Tewary, R.D.Kekatpure, M.L.Brongersma: Applied Physics Letters , 2006, 88[9], 093114 (3pp)