Pt thin films grown on MgO substrate from 100C to 600C , we observe the change in lattice parameter of Pt. like on 100C it was 3.94A' and 200C 3.95A' at 500C its was again at 3.94A' and at 600C it was 3.93A'.
the bulk value of lattice parameter for Pt is 3.92A'.
Hi Ali,
the lattice of MgO substrate or the atomic distances of MgO do not fit to those of the Pt.
Thus when depositing Pt at the MgO substrate the Pt atoms of the very first layers (e.g. the 1st and 2nd layer) primarily bind to MgO, but only a very few of them will set up a Pt-Pt bonding. In addition the very first Pt atomic layers will in general not set up a closed film. In consequence the succeeding Pt atomic layers will set up a distorted Pt lattice, having a lot of lattice defects. With increasing film thickness the successive Pt layers will have lattice spacings which approach the bulk one.
The temperature is just shaking the Pt atoms, giving rise to heal the lattice defects. So at more elevated temperature the healing of the Pt lattice defects more and more takes place just at touch down of the Pt atoms at the growing layer surface.
Thus your mean Pt lattice spacing of 3.94A gradually approaches the bulk value for increasing deposition temperature. In addition you observed increasing peak height, as you stated in a question some days ago, which is hint that you go for increased perfection of Pt crystall lattice with increasing temperature.
Remark 1: I would not overrate your lattice spacing value of 3,95A for the 200C case. The film thickness might be some what lower compared to the one you want to have.
Remark 2: I wonder that your starting lattice distance is 3,94A. You might have a significant Pt thickness, setting up an almost pefect Pt lattice. Do you have values for the film thicknesses in all your cases?
How did you measure the lattice parameter? Can you exclude sample misalignment or any other error? I am no expert for MgO but it would surprize me that it would show any animaly. The same for Pt. Therefore I would first look for possible sources of errors.
Thank you soo much Martens For your detailed answer, Unfortunately I was not able to find the thickness for all cases. But i should . Because its really important when we provide this kind of justification without thickness details. I was thinking that Lattice Parameter when i calculated it was in more then two digits, so some figures are rounded. @Nolze there is possibility of Error due to instrumental broadening or calculation precision. If i put the error bars in the graphs then It will not give us errors so big. But the good thing is that its Pt lattice parameter. :)
@ G. Martens: your explanation is certainly right, but I still do not know how the lattice parameters have been determined. If XRD, the range of a adapting lattice should be so thin that you should not detect this for materials like Pt. For less ductile it might be but even then only for very thin coatings (ie.e no relaxed material at all) and gracing incident geometry. If investigatet by TEM a big "question" is of course the relaxation of the removed lamellae (and preparation). Therefore again: How did you determined the lattice parameters?
Hi Gert,
according to a question of Ali some days ago (please see the link) he had performed XRD measurements.
But in general I must agree with you, the changes in lattice parameter are very, very small.
Perhaps Ali should for example repeat these experiments on much thinner films, e.g. 1/2 to 1/3 or 1/4 of the current film thickness (mass coverage) and look what happens then with respect to the lattice spacing of Pt (and XRD peak heights).
Just for a cross-check one (or two) measurements would be sufficient in order to see what's happening.
https://www.researchgate.net/post/Why_peak_Intensity_Increases_for_thin_films
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