I want to develop an AP-PECVD process. People have used nebuliser/atomiser for feeding monomer, in atmospheric pressure PECVD process .
For example, when we are depositing SiOx coating by PECVD at low pressure, the monomer HMDSO is heated and entered in reaction chamber in vapor phase.If we want to develop similar PECVD process at atmospheric pressure , do we require atomiser? If yes, then why it is required . Also, in this case , shall we first get droplets of particular size by atomiser and shall het it later to convert in vapor or we will inject droplets in liquid phase in the plasma regime.
There are a few possibilities to transfer the precursor into the atmospheric pressure plasma discharge. The each of them depends on the type of the equipment. For example atmospheric pressure plasma jet or dielectric barrier discharge. Moreover each of these method can also have intrinsic differences in the precursor feed approach. I will specify only two frequently used ways.
The first one is based on the transferring of the precursor by means of flow of the carrier gas (Ar, N2,O2) through the bubbler-flask with monomer. By controlling the flow rate of the carrier gas you will be able to regulate the amount of the monomer in the discharge. But you have to take into account that the choice of the carrier gas is of high importance as it strongly influences the plasma parameters and, consequently, the properties of the film. Such method good in case the monomer has relative high saturated vapor pressure.
The second one is based on the using of nebuliser. In this case the monomer should have a low viscosity, because in case the precursor has high viscosity, the aerosolized droplets will be relative big, which will influence the homogeneity of the result film.
Thank you Artem.
We are planning to use Dielectric Barrier Discharge with parallel plate configuration to deposit SiOx coating using HMDSO precurssor. For this experimental configuration, which precursor feed approach is more recommended ( bubbler flask or atomiser ) in terms of film uniformity and adhesion.
The HMDSO has a relatively high saturated vapor pressure and low viscosity. In terms of cost I recommend to use a bubbler-flask feed. The bubbler flask more cheaper than nebuliser. But anyway you can try both methods and compare the quality of the films.
For the APP diffuse DBD system the polymerisable precursor (HMDSO) and initiators may be introduced into plasma as a vapour, or as an atomised liquid. Usually, monomers are supplied to the relevant plasma-region after having been atomised. The atomiser can produce a coating-forming material with size from 10 to 100μm or more preferably from 10 - 50μm. However, getting atomiser (like ultrasonic nozzles, or vibratory atomisers) with optimize size will not be easier. So, bubbler flask that is readily available can be a better choice.
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