I sputtered a Ni-5.5Al (at%) target onto a glass substrate, suing DC magnetron. The thin film thickness is about 275nm.
The XRD on both sputtering target (bulk) and the thin film suggest that the grain orientation consists of AlNi (110) and Ni (200). However, I noticed that:
a) AlNi peak on the bulk is at 44.48°
b) AlNI peak on the thin film is at 43.38°
Attached is the XRD spectrum image.
Is the 1° different siginificant? Based on Bragg's law, this will show a difference in the lattice parameter. However, I am wondering if the result I am getting is negligible and if I only need to take note on bigger difference (e.g. more than 5°)?
The difference is due to film stress, which changes the film lattice parameters.
The difference is due to film stress, which changes the film lattice parameters.
1° in XRD can be significant especially at lower diffraction angles.
When you compare your XRD patterns on thin film and on bulk, you see that the diffraction angle is lower on your thin film indicationg that the interlayer distance is higher on your film compared to bulk.That is probably what Sabino said.
The second observation is the diffraction pattern is broader on your film. This can be originated from several things (crystallite size, stress,...)
For more details you could check for example these papers:
https://www.researchgate.net/publication/230153282_Thickness_dependence_of_electrical_and_structural_properties_of_Nb_thin_films
https://www.researchgate.net/publication/4306358_Superconducting_tunnel_junction_x-ray_detectors_with_ultra-low_subgap_current
Article Thickness dependence of electrical and structural properties...
Conference Paper Superconducting tunnel junction x-ray detectors with ultra-l...
In oder to be sure about stress, i would suggest you check with 2d XRD. in such a case is more sensitive than normal xrd...
Thank you all for the reply.
Dr. Sabino. thank you for the reference. Just so that I understand correctly - Based on the paper on Nb thin film, the stress on the thin film are from;
a) Internal strain (microstructure of film and impurities)
b) Thermal strain (thermal mismatch between substrate and thin film)
The stress effects the lattice parameter, hence the shift in peaks in XRD.
Since I am sputtering NiAl (crystalline thin film) on glass (amorphous), is it also possible that stress could have also come in the interlayer of glass-NiAl thin film during the initial growth, due to lattice mismatch?
Also, based on D.Zhong et. al, (2000), the initial particles that landed on the substrates might have grown as amorphous, then started to grow in crystalline from after it reached a certain thickness.
Should this is a possibility, would it be possible if I try to reduce the mismatch by increasing the substrate temperature, in order to provide more energy to the initial NiAl particles, so that it can grow as crystalline much earlier?
This shift could also be because of sample displacement error. Ensure it's not because of sample displacement error, then you can relate this shift to difference in the lattice parameter. Strain will cause a shift only if it's along one direction if it's random it will only broaden the peak.
Easy way to check if the shift is because of sample displacement error or lattice parameter change is to see how much the high angle peaks are shifted. Because sample displacement error is a function of Cos theta, and lattice parameter shift is a function of Sin theta.
By the way, One degree shift is significant.
@Muhammad: Sorry for answering late but last week I was on a trip and didn't have any free time. What you say is correct. For studying the effect of sputtering parameters on film stress I would suggest to use a very simple technique. I know I have published it some results with that technique several years ago but I cannot recall where.
Prepare several substrates by covering them with a photoresist film. Then sputter a NiAl film on one/two substrates in turn, changing the deposition conditions on each run, e.g., the substrate temperature (pay attention that photoresist cannot be heated too much!) or deposition rate, or whatever you might consider meaningful.
The films with larger stress will damage the photoresist film, causing breakups in the worst cases or at least corrugating it. It is then easy to relate the sputtering parameters to the amount of damage of the photoresist layer, i.e., to the film stress.
Dr. Sabino,
Thank you for the advice. This is the first time I came across such method , am truly grateful for it!
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