I have prepared CrAlN coatings. During deposition, every careful steps were taken to avoid any oxygen leakage or contamination inside the chamber. but still after XPS investigation the oxygen content is almost 10 at%. This was cross-checked with TEM-EDS data too. Can anyone suggest any other reason that can explain the presence of oxygen content in the coatings ?
What is your base vacuum? and other operating condition like operating pressure?
Which substrate you are using?
The reason may be due to hydrocarbon out gassing emitted from your chrome plate base. Some contribution can be due to atm air contamination during sample packing, unpacking, and measurements.
To solve the problem, the electroplating process (if you are using), cleaning process, and PVD coating parameters (if you are using) required modification.
These info may be useful! Good luck.
Basically answer for yourself the ffollowing questions on the main 3 important factors
1. Materials; are my materials of the right composition and purity?
Check the suppliers data sheet and when in doubt do chemical analysis.
2. Tool: Is my tool in proper condition: is it leak free, does it have good low base pressure, does it have low partial oxygen pressure, are the gaselines leak-free? Are there any substrate holders used which could degas?
Best way to check all this is to hook-on an RGA and do a thorough vacuum analysis fo your system.
3. Process: Is my process oxygen free; do I use the proper conditions (gases, pressure, power, etc) to create CrAlN. Are the gases I use of high purity? Is there a chance you properly deposit the material but it get's oxidized once it comes into atmospheric pressure again?
I could help you further if you give more information on materials, tool and process settings.
First ensure high purity argon for your sputtering process.
You can use an Argon inert gas purifier
Your tubing from the gas cylinder, connectors in-between the cylinder and chamber should be minimized, and the length of gas line tubing should be as short as possible.
Achieve a good level of vacuum before you insert your gases. Liquid nitrogen traps are useful to achieve a good base vacuum.
Peter Knapen has rightly suggesteded to hook up a RGA, although a little expensive,but extremely useful for reactive sputtering. You can also have a plasma diagnostic tool to monitor you plasma.
K. Sreenivas
Check your gas flow rate when sputtering. Increase argon gas rate by modifying turbo pump shutter. If argon gas rate is flow chamber walls will vomit oxygen
There is a simple rule for phys-adsorption: there is one monolayer adsorbed molecules per second under 1e-6 Torr pressure in vacuum chamber. If you use turbo pump and have no a cryo panel the main residual gases are: N2, H2O, H2, CO2. In your case the aluminum is a very strong getter, which adsorb oxygen and form oxide easy.
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