How it your magnetron configuration, is it confocal sputtering, or two in-line magnetron with rotating substrate holder?

The curvature of the film indicate stresses

@Emile Haye it has a confocal configuration with a rotating substrate

Ok, and when you used single target, did you also use the rotating substrate holder?

Yes I did.

I would say that the use of a second target generate stresses, due to different direction of the species flux, but this is generally not observed.

Another explanation is the lower power that you used: at 2x150 W, you provide much less energy to atoms, and they have less energy to diffuse and arrange themselves at the film surface, that generate more stresses.

Try to sputter at 2x300W, and decrease the deposition time.

Regards,

Emile

Thanks for the suggestion, I have tried 2x300W as well, I was not even able to get a free standing film. The adhesion was too high that the film did not even release from the substrate. But I will try with less deposition time.

I have one more question to ask as well. The deposition parameters which I mentioned in the question did not work when I tried to deposit 15microns even with a single target. I was thinking of epitaxial strain, but the film I am depositing is amorphous. I could not reason why it is not working. Do you have any idea why?

Thanks and regards,

Balasubramanian S

If you increase the thickness too much, the level of stresses increase, that is the reason that you have breaking of the film. You have to find the optimum thickness to get you free standing film.

Regards,

Emile