I agree with Xuhua - the thickness of Cr should be minimum 5 nm and the thickness of Au 50-60 nm. Also, before deposition of contacts you have to be sure that the surface of your glass substrates is clean. I would recommend such a procedure: cleaning of the substrates using a detergent (e.g. Decon), high purity deionized water, acetone, and finally, methanol. Then, blow dry with nitrogen gas. If you want to be sure that your substrates are (super) clean, I would additionally do either oxygen plasma or UV/ozone treatment.

I hope it helps!

Dear Emily,

Firstly the thickness of your chromium and gold layers are crucial for such application. The typical thickness what we did is 5nm Cr and 50 to 60nm gold, respectively.

Secondly the surface cleanin of the glass substrates also affect the adhension. Some surface treatment for sure will help the coating on the substrate.

Hope it helps.

Xuhua

Adhesion of thin films with an interface layer is tough, a lot has to do with the surface preparation, as Dr. Wang illustrates. Also a quick read shows that chromium may oxidize alcohols under acidic conditions, and that the chromium species is a participant in the reaction. With thin films, I wonder if this may be your de-lamination mechanism (dissolution of the chromium layer). Check "ethanol reaction with chromium" in Google Scholar and see if there is anything there. Would also explain the polymer passivating the reaction by sealing the chromium. Best of luck with experiments!

I agree with Xuhua - the thickness of Cr should be minimum 5 nm and the thickness of Au 50-60 nm. Also, before deposition of contacts you have to be sure that the surface of your glass substrates is clean. I would recommend such a procedure: cleaning of the substrates using a detergent (e.g. Decon), high purity deionized water, acetone, and finally, methanol. Then, blow dry with nitrogen gas. If you want to be sure that your substrates are (super) clean, I would additionally do either oxygen plasma or UV/ozone treatment.

I hope it helps!

Alternatively, you can also use Ti to improve gold adhesion instead of Cr.

To make sure that the electrodes are not detached, I like to use 10 nm of Ti or Cr for 50 nm of Au.

All the best ;)

totally agree with the answers here. Chromium adheres perfectly to both glass and Au, the reasons for Au flakes in solutions would be:

1- unclean glass - and use the solvent cleaning steps mentioned by Leszek A. Majewski , and preferably also followed by oxygen plasma in an Asher (no need for high power or long treatment). One important thing is to move the samples straight to the deposition chamber straight away after plasma

2- too thin adhesion layer - If you are using thermal evaporator, I would recommend to use at least 7nm of Cr, but don't make it too thick though, and 50-60nm Au should be good.

Thank you for all your useful responses.

We've been using a Cr layer that is 10 nm thick so I would have thought that would be thick enough, but equally this may be the issue itself as the layer is too thick maybe? The evaporator itself is also having problems which hasn't helped!

I will be sure to try out your suggestions with the cleanliness of the substrates beforehand. We already clean using various solvents but haven't tried using ozone treatments which is something we shall try.