Low Temperature Non-equilibrium Methane Plasma Atomic Emission Spectrometry Diagnostics

In recent decades, great achievements have been acquired in the preparation of new function materials including various films with the development of low pressure plasma chemical vapor deposition. However, the growth mechanism of some films in the process of plasma chemical vapor deposition (PCVD) remains unclear. At present, the development of the plasma diagnosis in situ in the process of the deposition is of great importance. There are many methods used for the plasma process diagnosis, wherein optical emission spectroscopy (OES) is a powerful diagnostic tool—a simple method without disturbing the reactions. In this thesis, we studied the distributions of different radicals in the CH₄/He, CH₄/H₂ plasmas and the variations of the relative intensities of these radicals with different experimental conditions such as the input rf power and the gas pressure.It was showed that the emission lines of H, H₂ and CH radicals had been identified in the methane plasma in the two systems. In the CH₄/He system, the intensities of these active species are initially increased and then decreased as increasing the input rf power, and as the gas pressure increases, the intensity of the CH radical is always decreased, the intensities of H_α, H_βand H_γspecies are initially increased and then decreased; In the CH₄/H₂ system, the relative intensities of H_α, H_β, H_γand CH radicals are increased as increasing input rf power, and the relative intensities of all these radicals are initially increased and then decreased as increasing of the discharge pressure. These experimental results offer the basic data for understanding the process of hydrocarbon thin film deposition.