Hi All,
I have prepared the CH3NH3PbI3 perovskite powder and CH3NH3PbI3 film. The powder and Thin films shows two different pattern which are consistent with reported literature. However, i need the reason behind this change. Please someone provide me the information with reference.
Thank You
Dear Khursheed Ahmad,
you may share your diffractograms.
But nevertheless I think the difference is clear; compared to your powder pattern the film does not show all of the XRD peaks at same (relative) heights and some peaks may have been vanished at all.
This effect is attributed to the (partial) preferred orientation of the crystallites in the thin film compared to the random orientation of crystallites in the powder case.
Peak boadening due to different crystallite sizes in the film compared to the powder case may also give rise to peak height differences as well as peaks broadening and thus peak height reduction due to residual stresses in the film.
In the case thin film you may also 'see' the substrate. So here additional peaks (from the substrate) or even a (more or less structured) continous background may show up.
You see, there are a lot of possibilities for upcoming differences of XRD pattern of the nominal same material.
Please 'google' for 'preferred orientation', 'Scherrer-equation' and 'Williamsen-Hall Plot' or search for these buzz words via the RG search button at the top of each RG-page.
Good luck.
Dear Khursheed Ahmad,
you may share your diffractograms.
But nevertheless I think the difference is clear; compared to your powder pattern the film does not show all of the XRD peaks at same (relative) heights and some peaks may have been vanished at all.
This effect is attributed to the (partial) preferred orientation of the crystallites in the thin film compared to the random orientation of crystallites in the powder case.
Peak boadening due to different crystallite sizes in the film compared to the powder case may also give rise to peak height differences as well as peaks broadening and thus peak height reduction due to residual stresses in the film.
In the case thin film you may also 'see' the substrate. So here additional peaks (from the substrate) or even a (more or less structured) continous background may show up.
You see, there are a lot of possibilities for upcoming differences of XRD pattern of the nominal same material.
Please 'google' for 'preferred orientation', 'Scherrer-equation' and 'Williamsen-Hall Plot' or search for these buzz words via the RG search button at the top of each RG-page.
Good luck.
Dear Khursheed,
In powder form, all the particles are randomly oriented in different directions. Hence, when X-ray beam is allowed to fall on it, peak broadening effect may obtained. However, when the film of the same material is formed, all the particles get one defined orientation (ordered). Hence, when X-ray beam is allowed to fall on the film, somewhere the vibrations get restrictions. Therefore the difference in powder and film form may be possible though the material is same.
It will be more helpful if you are sharing the results for discussion.
Dear Colleagues,
XRD pattern of even fully randomly oriented material in thin film differs from that of powder, because the scattering volume in a film is much stronger Theta dependent than in the powder.
As the path in the film of thickness t is 2*t/sin(Theta), the intensity ratio I1/I2 of two reflections at Theta_1 and at Theta_2 are different in powder and thin film. For very small t (
Thank you very much for valuable answers prof. Mark O. Rikel and Gerhard Martens. These answers helped me a lot.
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