I deposit Ag on Si substrates using thermal evaporation technique and the thickness results are not consistent. Scotch tape test has shown that the adhesion of Ag to the substrate is quite poor. I have used Al as the interlayer, also changed the substrate to SiO2, but did not help. I wonder if this poor adhesion could impact the final thickness of the thin film that I measure using AFM? Any suggestions on improving the adhesion of Ag to the substrate is also very appreciated? Thanks in advance.
I am not sure if Al is the right candidate for adhesion improvement. People generally use Cr. Check the lattice parameters. the thumb rule is to choose the materials without lattice severe mismatch.
Also, you may check the vacuum of your system. if you are using the conventional evaporator (one with Molybdenum or tungsten Boat), the adhesion is directly proportional to the vacuum.
Additionally, surface treatment could be one option. Proper cleaning of your sample plays a crucial role in adhesion.
Dear Roksana Bavand ;
The adhesion energy of coatings increases with the coating thickness. you can increase the coating thickness to get a more stable coating. When silver deposited at very small thicknesses (
Hi,
I also used Cr as a seed layer. Another means of improving substrate adhesion is to heat the substrate. I recall a rule-of-thumb that states, 'a monolayer of impurities per second form on a surface at 10E-6 mbar'. So improving your vacuum, as mentioned above, would help. As would reducing impurity sticking probabilities by heating your substrate.
It may also be the case that variations in initial vacuum and deposition rate may also be factors that contribute to your variable results.
Dear Roksana Bavand ,
Cr or Ti are tipically used as intermediate layer to improve adhesion. However, if you are using AFM to measure thickness, it is more important how do you create the step height to be measure . Can you describe how do you create it?. Also, can you show a couple of AFM images to get a better idea of how do you perform the thickness measurement and the discrepancies to mention?.
Even though there are many factors that affect the adhesion such as the cleanness of the substrate, the quality of the vacuum, the temperature of the substrate at which the deposition is made, the rate of deposition, the deposition of an intermediate layer, etc., in regard to the strict relation between adhesion and thickness of the deposited film, higher its thickness higher the inner structural stress and so lower the adhesion (higher the tendency to peel out), but slower the rate of deposition and an optimized temperature of the substrate are also beneficial.
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