In the vacuum system of high PVD vacuum coating equipment
In the vacuum system of high PVD vacuum coating equipment, after heating the metal filament, the partial pressures of water vapor, carbon monoxide and methane increase. The increase in these gases is related to the presence of hydrogen. After reducing the partial pressure of hydrogen, the partial pressure of these gases also decreases. Since hydrogen is decomposed into an atomic state and diffuses into the metal, it is chemically active and easily reacts in the metal and on the surface. In the vacuum system, a variety of chemical reactions can be carried out simultaneously on the metal wall and the glass wall. The history and use conditions of various materials are different, and the gases generated by chemical reactions are also different. Under extremely high vacuum conditions, gases other than hydrogen are related to the presence of hydrogen. Therefore, reducing the partial pressure of hydrogen is still the main thing.
Film uniformity concept of vacuum coating machine
1. Uniformity in thickness:
It can also be understood as roughness. On the scale of optical film (that is, 1/10 wavelength as a unit, about 100A), the uniformity of vacuum coating is quite good, and the roughness can be easily controlled at 1/of the wavelength of visible light. Within the range of 10, that is to say for the optical properties of the film, there is no obstacle to vacuum coating. But if it refers to the uniformity on the atomic layer scale, that is to say, to achieve a 10A or even 1A surface smoothness, the specific control factors will be explained in detail below according to different coatings.
2. The uniformity of chemical composition:
That is to say, in the film, the atomic composition of the compound will easily produce uneven characteristics due to the small size. For the SiTiO3 film, if the coating process is not scientific, then the actual surface composition is not SiTiO3, but may be other proportions. The coated film is not the chemical composition of the desired film, which is also the technical content of vacuum coating. The specific factors are also given below.
3. Uniformity of lattice order:
This determines whether the film is single crystal, polycrystalline, or amorphous, which is a hot issue in vacuum coating technology.
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