Deposition of silver on glass by e-beam evaporation

The case

I am attempting to use silver evaporation pellets to deposit one-micrometer thick silver layer on the glass substrate. I found that only electron beam evaporation is accessible within the facility. I tried Ag/Ti/glass but silver peels off the Titanium layer. Up to now, only Ag/Au/Ti/glass can partially work, and only 1/2 of my samples were fully coated with silver; the other half turned into blackish-rainbow color. I wonder what is wrong in the process? Should I should some intermediate layers?

deposit silver on glass substrate
deposit silver on the glass substrate

Possible Cause and Solution

The thickness of the Titanium (Ti) layer may be too large. Generally speaking, 5 to 10 nm is enough in this case.

The process is not operated in a good vacuum condition, thus the titanium layer is oxidized. In electron beam evaporation, as well as other vacuum evaporation, the vacuum degree of the evaporator is extremely important, which will greatly influence the quality of the film obtained. Thus, please make sure the vacuum chamber is well sealed before evaporating.

It is hard to avoid that the evaporated silver (as well as gold) only loosely connected to the glass substrate. Cleaning the glass with acetone and then methanol could help. Or you can just replace the glass substrate by using another transparent substrate, such as Al2O3, SiO2, AlN and Diamond. The silver layer can better deposit on those substrates mentioned above.

Other Suggestions

Titanium is an excellent adhesion layer, but it is also true that it may lose some of its adhesiveness if the vacuum is not good enough. As for its alternatives, Chromium (Cr) and Aluminum (Al) are recommended to act as the adhesion promoter.

Rising the temperature up to 100℃ in the vacuum for a few minutes may also improve the adhesion of metals.

Silver (Ag) Evaporation Materials
Silver (Ag) Evaporation Materials

For the explanation of the terminologies of vacuum coating mentioned in this passage, please refer to Terminologies of Vacuum Evaporation.

For high purity silver evaporation materials, please visit Stanford Advanced Materials.

For more news and knowledge about vacuum coating, please see SAM News.

PVD vs. CVD: What’s the difference?

PVD vs. CVD: What’s the difference?

In recent years, physical vapor deposition (PVD) and chemical vapor deposition (PVD) have wide applications in various industries to increase the hardness of tools and molds or apply beautiful colors to the products. Thus these two methods are considered as the most attractive surface coating technologies. Then, using the example of cutting tools, let’s make a detailed comparison between these two methods.

Definition

Physical vapor deposition (PVD) uses low-voltage, high-current arc discharge technology under vacuum conditions to evaporate the target and ionize the vaporized material and the gas, and finally make the evaporated material and its reaction deposited on the workpiece.

Continue reading “PVD vs. CVD: What’s the difference?”

Differences between vacuum evaporation and sputter coating

It is well known that vacuum coating has two common methods: vacuum evaporation and sputter coating. However, many people have doubts about the difference between evaporation and sputter coating. Let SAM Sputter Targets answer it for you.

sputter coating3First, let’s take a look at the definition of these two words. The vacuum evaporation is carried out by means of resistance heating, electron beam or laser bombardment in an environment with a vacuum of not less than 10-2 Pa, and the evaporation material is heated to a certain temperature to evaporate or sublimate a large number of molecules or atoms, and then directly deposited on a substrate to form a film. Continue reading “Differences between vacuum evaporation and sputter coating”

Five evaporation sources for heating

The evaporation source is a heating element used to vaporize and vaporize the molding material. The evaporation sources currently used mainly include the following types:

Resistance evaporation heating source

The resistance heating method is simple and easy to operate, and is a common application method: a filament-like or sheet-like high melting point metal (such as Tungsten, Molybdenum, Titanium, etc.) is made into an evaporation source of a suitable shape. It is equipped with an evaporation material to turn on the power supply, and the evaporation material is directly heated and evaporated. The resistance heating method should mainly consider two problems, the melting point and vapor pressure of the evaporation material; the reaction of the evaporation material with the coating material and the wettability caused by the coating material.

Electron beam evaporation source

The evaporation material is placed in a water-cooled copper dry pot and directly heated by an electron beam, which is called electron beam heating. It can vaporize the evaporation material and form a film on the surface of the substrate. It is an important heating method and development direction in the vacuum evaporation coating technology. In the resistance heating method, the coating material and the evaporation material are in direct contact, and the temperature of the evaporation material is higher than that of the coating material, and is easily mixed into the coating material, especially in the semiconductor device coating. Electron beam evaporation can overcome many shortcomings of general resistance heating evaporation, and is particularly suitable for preparing high melting point film materials and high purity film materials.

High frequency induction heating evaporation source

The high-frequency induction heating evaporation source places the graphite or quartz crucible containing the evaporation material in the center of the water-cooled high-frequency spiral coil, so that the evaporation material generates strong eddy current loss and hysteresis loss under the induction of the magnetic field in the high frequency band (to Ferromagnetic), causing the evaporating material to heat up until evaporation. The smaller the volume of the evaporated material is, the higher the frequency of induction is. In the large-scale vacuum aluminum plating equipment on the steel strip, the high-frequency induction heating evaporation process has achieved great success.

Radiant heating evaporation source

For materials with high absorption of infrared radiation, it can be evaporated by radiant heating, and many substances are evaporated by this method. In addition, the reflectivity of the metal for infrared radiation is high, and the absorption rate of quartz for infrared radiation is low, so they are difficult to be evaporated by radiation heating. The main advantage of the radiant heating method is that the evaporation is only heated on the surface, and the adsorbed gas is released on the surface without splashing the material.

Laser beam evaporation source

The evaporation technique using a laser beam evaporation source is an ideal film preparation method because the laser can be installed outside the vacuum chamber. This not only simplifies the space arrangement inside the vacuum chamber and reduces the abandonment of the heating source, but also completely avoids the contamination of the evaporation material by the evaporator, thus it is advantageous for obtaining a high-purity film.

 

Stanford Advanced Materials (SAM) Corporation is a global supplier of various sputtering targets such as metals, alloys, oxides, ceramic materials. If you are interested, please visit our website https://www.sputtertargets.net/ for more information.