Vacuum Evaporation Coatting
High melting point
Low saturated vapor pressure.
Stable chemical properties
Good heat resistance.
Rich in raw materials, economic and durable.
Vacuum evaporation coating
In the vacuum chamber, the raw material of the film to be formed in the vessel is heated and its atoms or molecules are vaporized from the surface to form a vapor stream which is incident on the surface of a solid (called a substrate or substrate) to form a solid film method.
The main physical process due to vacuum evaporation or vacuum deposition is produced by heating and evaporating the material, so it is also known as thermal evaporation.
Evaporation source-Boat, Crucible, Heater in W and Mo materials
Evaporation source is a key component of the evaporation device, most of the metal materials are required in the 1000 ~ 2000 ℃ high temperature evaporation. Therefore, the evaporation material must be heated to a very high evaporation temperature.
Materials: Molybdenum, tungsten, tantalum and other high melting point metal,
Advantages: evaporation source structure is simple, cheap and easy to make
Disadvantages: need to consider the material and shape of the evaporation source
(1) High melting point
(2) Low saturated vapor pressure.
(3) Stable chemical properties
(4) Good heat resistance.
(5) Rich in raw materials, economic and durable.
In the film process, the commonly used evaporation source materials are W, Mo, Ta, etc., Table 1 lists the main physical parameters for W, Mo, and Ta.
The wettability of the vaporized material and the evaporation source material is related to the surface energy of the vaporized material, which may be considered to be readily wettable when there is a tendency to expand on the evaporation source;
If it is agglomerated on the evaporation source and close to the formation of spherical tendencies, it can be considered difficult to wet.
In the case of wetting, the evaporation of the material takes place from the large surface and is relatively stable, and it can be considered as the evaporation of the surface evaporation source; in the case of little wetting, it is generally considered to be the evaporation of the point evaporation source. If it is prone to wet, the evaporation material is very compatible with the evaporation source, the evaporation state is stable; if it is difficult to wet, when using the filamentous evaporation source, the evaporation material is easy to fall from the evaporation source.
Depending on material characteristic and combined with the wetting properties of the evaporation source material, the evaporation source may make into vary shape and select different evaporation source materials .