Microstructural analysis of the modifications in substrate-bound silicon-rich silicon oxide induced by continuous wave laser irradiation

Laser-irradiation of silicon-rich silicon oxides (SRSO) is a promising technique for spatially well-defined production of silicon nanocrystals (nc-Si) showing room temperature photoluminescence. In this work, we use continuous-wave (CW) laser processing to generate nc-Si in SRSO films on fused silica substrates. One main problem is damage introduced by laser processing which results in a porous layer beneath the original film surface as is consistently shown by electron tomography and energy-dispersive X-ray spectrometry. Processing conditions for damage-free nc-Si formation are identified by systematic variation of laser intensity and measuring the depth of the damaged region by transmission electron microscopy (TEM). By combining TEM imaging and analysis it is shown that the damaged region has a composition close to SiO2 which is due to a predominant loss of silicon rather than an a result of surface oxidation during laser processing.