In my study, I used annealing treatment to improve the crystallinity of thin films. After annealing, the XRD intensity (the (0002) peak in theta two-theta mode) enhanced dramatically but the FWHM remain the same.
I found that the grain size can be calculated from FWHM of XRD by scherrer equation and some papers said that the vertical grain size was limit by the film thickness. Does it mean that the FWHM of XRD peak was also limited by the film thickness so the annealing treatment only enhanced the XRD intensity?
Thanks
If the FWHM remains the same but intensity is increased you may have induced preferred orientation on the basal spacing by the annealing process.
As a general trend, when film thickness increases grain size also increases. However, with annealing, generally, smaller grains agglomerate with each other and make bigger grains which increases the crystalline quality and grain size. In ur case, i agree with Ian that you may have induced preferred orientation with the same grain sizes.
I agree with my colleagues here but want to add that of course the Scherrer equation only works if the FWHM is mainly due to the grain size. A certain amount of peak broadening can also arise from stress (see "Williamson-Hall plot"), and from the resolution of your setup.
First thing is : What you calculated using FWHM of XRD peak by Scherrer's equation is the Crystallite Size. Whereas a Grain consist of many Crystallites.
The reason for the increment in the intesity of the peak with no change in the FWFM is simply the increase in the crystallinity of the films after annealing. Number of Oxygen vacant positions are filled by O annealing, giving rise to perfecting the local crystallites.
By changing the film thickness, there will be a change in the strain only.
I'd like to know that can the Crystallite Size calculated by FWHM of XRD be greater than film thickness? If not, can we say that the FWHM was also limited by film thickness?
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