PLASMA STREAM PROCESS TOOL
A plasma jet is a plasma source where a pair of metal electrodes with a sharp point, contained in a cylinder made of dielectric material, and is connected to a high voltage generator. A stream of Helium or Argon is blown in the insulated cylinder so that the electrode finds itself in contact with the gas. Due to the high electric field near the electrode’s sharp point, Helium or Argon ionizes and a mixture of electrons, ions and metastable atoms and molecules is blown by the flow stream towards the exit nozzle. This mixture of plasma species survives for a few centimetres outside the nozzle, until ambient species (oxygen, water vapour, carbon dioxide, nitrogen, etc.) contained in the air quenches the plasma. In our machine the plasma jet is mixed with an aerosol of liquid precursor chemicals so that, positioning the jet above a material, it is possible to have a deposition of a coating with particular chemical and physical properties. The aerosol is obtained using a nebuliser which is propelled by the process gas. As soon as the liquid precursor is nebulized it finds itself immersed in a zone filled with plasma. The high energetic electrons, ions and metastable species trigger plasma chemistry reactions on the droplets’ surface and, if a substrate material is placed in contact with the plasma jet, the highly reactive droplets deposit on the material surface and further react with the plasma species which impinge on the surface. The result is a deposition of a coating on the substrate which retains the particular physical-chemical characteristics of the original precursor liquid.