The mechanism of plasma cleaning is mainly the physical and chemical effects of active particles. Therefore, when cleaning different materials, selecting the correct medium gas can achieve twice the result with half the effort. According to the reaction mechanism, there are two types of gases, one is reactive gas ( chemical action ), mainly hydrogen, oxygen, etc. ; the other is non-reactive gas ( physical action ), mainly argon, helium, nitrogen. 

The common use of gas in plasma cleaning machine is as follows : 

Oxygen plasma : high-energy oxygen ions can burn off the surface of the organic matter, cleaning speed, the effect is obvious, but may oxidize the material. 

Hydrogen plasma : Removal of metal surface oxides by excited free radical hydrogen .

argon plasma : ion mass is large, in the state of electric field acceleration by impact power sputtering to remove pollutants, or cracking the chemical bonds of organic matter to form gas volatilization, can also remove the metal oxide film, but the cleaning effect is weak. 

Ammonia plasma : Ammonia treatment can significantly improve surface roughness, improve wettability, and increase the number of nitrogen-containing groups on the surface of the material. It is one of the most significant gases for plasma cleaning. However, ammonia is not friendly to the atmospheric environment, and sewage treatment brings great pressure to large-scale industrialization. 

Fluorine-containing gas : After plasma treatment, fluorine-containing gas is bonded to fluorine-containing functional groups on free radicals, thereby greatly improving the surface hydrophobicity of the material. 

In addition, if you want to introduce functional groups on the surface of the material, the surface of the material can be treated with N2, NH3, O2 and other gases, and the corresponding functional groups such as-NH2, -0H, and-COOH can be introduced, especially for polymer substrates. These functional groups can significantly improve the wettability, adhesion, and reactivity of the substrate.

In the plasma cleaning process, two or more mixed gases can also be filled to obtain a better cleaning effect. For example, the combination of argon and oxygen, argon ions use physical bombardment to clean the surface dirt, and oxygen reacts with the surface dirt. When argon and oxygen molecules collide, the charge can be converted and combined to form a new active principle, so that the ionization and ion energy can be greatly reduced, and more active particles will be generated. At this time, the cleaning effect has reached 1 + 1 > 2. However, when a variety of gases are filled, there are more factors to be considered. For example, the higher the purity of the selected hydrogen is, the more hydrogen ions will be generated, and the corresponding cleaning oxide will be faster. Although the reaction efficiency is improved, hydrogen can not be ignored as a flammable and explosive gas, which has a high risk. Therefore, when considering the filling of mixed gases, hydrogen and argon and other gases are usually filled together. The proportion of hydrogen should be in a relatively safe position to maximize efficiency. Cleaning different substances also needs to explore better methods and processes to continuously improve the cleaning effect.