Si and SiO detection in a HMDSO/propane/air flame using spatially resolved optical emission spectroscopy (OES)

Optical emission spectra of rich HMDSO/propane/air and propane/air flames (equivalence ratio Phi=1.33) were recorded using an imaging spectrometer in combination with an intensified CCD camera. The probe area was about 1 x 0.2 mm(2). This is small for the OES signal and allows scans of high spectral and spatial resolution across the flame. Emission lines of Si* (similar to 252 nm) and SiO* (220-265 nm) were registered at different heights above the slit burner. Si* and SiO* were found up to 10 and 40 mm above the burner, respectively. Up to a HMDSO concentration of 0.015% in the total gas flow a linear dependence between Si* and HMDSO concentration could be proved. Gas temperatures were determined using Raman scattering by N-2 molecules and compared with temperatures derived from simulations of CH* (A-X) and OH* (A-X) spectra. N-2 and CH* temperatures are within (1950 +/- 50) K and (2400 +/- 500) K in a good agreement, respectively. At a height of 12 mm above the burner the OH* (A-X) molecules have a temperature of (6700 +/- 500) K. We suggest to position substrates for coating applications in a distance of 8 to 10 mm from the burner to use the high OH* concentration for SiO2 layer deposition. (C) 2012 Elsevier Ltd. All rights reserved.