Optical spectroscopy of emission from SiSiOx nanoclusters formed by laser ablation

This paper reports an experimental study of optical emission from SiSiOx nanoclusters in a laser-induced plasma plume produced by conventional laser ablation techniques. Emission spectroscopy and optical time-of-flight measurements (TOF) were carried out during reactive ablation of Si targets in He, Ar or O2 atmosphere. Several broad emission bands detected and identified as emission from Si nanoclusters formed at early stage of laser induced plasma expansion. The bands observed show a good spectral correlation with photoluminescence bands of SiSiOx nanoclusters thin films and Si nanoclusters absorption bands. Analysis of plume dynamics showed considerably slower translational velocities and broader energy distribution of nanoparticles than those of neutrals and ions. From TOF measurements large spectral band widths can be explained by superposition of radiation from the clusters of different size. Two fluxes of clusters, forward and reversed, found within the plasma plume. Their spatial behavior and pressure dependence can be explained by the character of their motion, which is determined by complex hydrodynamics of plume expansion.