Investigation of silicon oxide emission spectra observed in a pulsed discharge and a laser-induced plasma

Abstract

Emission spectra of silicon oxide molecules in the spectral range from 228 to 246 nm have been observed in a pulsed discharge and a laser-produced plasma. The vibrational bands belonging to the υ = −1, 0, +1 sequences of the SiO A 1 -X 1 + system have been reproduced by computer simulations in order to determine the vibrational and rotational temperatures. In the pulsed discharge, the vibrational temperature has been found to exceed the rotational temperature several-fold, indicating the non-thermal character of this type of plasma. In contrast, similar values of the two temperatures have been deduced for the plasma produced by pulsed-laser ablation, proving a collisional equilibrium. Simple criteria based on intensity ratio measurements are proposed for the temperature evaluation from the SiO emission bands.

Vacuum-Ultraviolet Photoionization Measurement and ab Initio Calculation of the Ionization Energy of Gas-Phase SiO2

“…The sublimation temperature of Si is ∼3500 K. This would suggest that the temperature in our ablation source will be at least this temperature since we need Si atoms to prepare SiO 2 . A number of experiments , suggest high rotational and vibrational temperatures of SiO species generated in laser ablation of Si in a low-pressure oxygen environment using laser spectroscopy. Hermann et al state that the plasma is in a partial local thermal equilibrium and has a temperature of 3500 K. Collisions in the molecular beam under our conditions would lower the temperature, but it is plausible that incomplete cooling would give rise to the low-lying vibrational states and hence lower the appearance energy of SiO 2 .…”

Insight into the plasma oxidation process during pulsed laser deposition

“…[12] Several efforts based on optical OES, [13] absorbance or fluorescence spectroscopy, Langmuir probe (LP) [14][15][16][17] or even mass spectrometry techniques [18] have been made. Important data are available for SiO, [19] ZnO, [20] VO 2 , [21] TiO [22] or TiO 2 , [23] La x Ca 1−x M-nO 3 [9] and even for Pu x O y , [24] with special attention paid to silver oxides (Ag 2 O or AgO) [14,25,26] for their p-type conductivity properties and chemical instability. LP investigations of Ag in O 2 led to the postulation of three pressure regimes: (i) a vacuum-like regime, (ii) a transition regime with plume splitting and (iii) a shockwave formation and diffusion regime.…”

Strong emission of particulates towards the incident beam direction in pulsed-laser ablation experiments

“…The plume formed during deposition experiments was clearly visible by the naked eye and it was recorded by a digital camera (Panasonic NV-DS28EG). We assume that the neutral and ionized Si monomers are responsible for the radiation emission in the visible and UV regions [20,21]. The observed angle of the plume deflection as a function of the number of laser pulses per site was reported elsewhere and its relation with the target morphology has been extensively reported [13].…”