This is very interesting. I would expect that the bond from NiCr to KBr would be weaker than its bond to silica, which could explain the different result. Perhaps the gold layer forms an alloy with the NiCr that makes its (already weak) bond to KBr weaker? Does it matter how thick the NiCr layer is? Another possibility is that the CTE mismatch becomes worse with the presence of gold... although since the gold layer is very thin, this does not really make sense. Honestly I am not sure why this should happen.

In our test NiCr layers are 50-60 nm. First we tried regular 70 nm of Au on top and it's lifts off as a single film. We reduced gold layer to 20 nm, same lift off. When we deposited only NiCr layer on KBr it stays on 70-100% of the surface. When NiCr layer on we can feel tape actually sticking to it and we have to be careful not to damage crystals. With NiCr/Au layers it peels off from KBr easily. Like there is no bond between NiCr and KBr

Vsevolod,

Are you putting down a NiCr alloy, or a layer of Ni followed by a layer of Cr? I know in many power electronic circuits Ni is used as a diffusion layer barrier for Au. If you must put down a NiCr alloy first, I would suggest then applying a decent (~50+ nm) diffusion barrier layer of pure Ni, followed by your Au top layer (I assume to block oxide formation).

Good Luck!

George Peterson

We are putting 80/20 NiCr alloy. We don't have tools to do 3 layers without exposing work to air. Wouldn't Ni oxidize as soon as air introduced?

Vsevolod,

Yes, Ni will oxidize almost immediately when exposed to atmosphere. Is there something special about the KBr/NiCr interface? The other option would be to calculate the diffusion length of Au in NiCr (80/20) at the working temperature and deposit a layer sufficiently thick that Au cannot possibly reach the contact. But at an elevated temperature that may be microns of NiCr...

Sincerely,

George

Our film specifications only up to 100C, so should not be an issue. What thickness of NiCr you would recommend?

Vsevolod,

As I said, you will have to do some searching to see how diffusive Au is in 80/20 NiCr. But if you just wanted to give something a shot to see if you can block it, I found that Au would diffuse through ~200 um of Alumina at room temperature as part of my previous research (shorted out the insulating layer of my device). I would start with something larger than that.

Sincerely,

George Peterson

Au will diffuse in the prepared thin films by aneaking the NiCr at least 980 C.or uou can added Au to NiCr in the demand ratio and prepare ternary alloy

Thank you very much for answers. We tried higher amounts on NiCr during depositions and it didn't work. The problem was in our deposition speed. Initially we were going about 5-10 A/s and NiCr layer wasn't adhering and actually was peeling off on its own from surrounding surfaces. When we reduced speed of deposition to .7-1 A/s, it gave us stable adhesion results and better uniformity layer. Unfortunately due to technical reasons we haven't performed NiCr+Au thin film depositions.

Polymer mostly orepared by casting method by choising the lrper solvant to the polymer then by using msgnetic stirrer one can get solution then left to dried at room temperature

The preparation of polymer on any bulk salt as substrate have many problems like hard adhesion so I ususlly used casting method