I have prepared Nb doped TiO2 thin film by RF magnetron sputtering. I am getting gradual increase in FWHM and decrease in crystallite size calculated using Scherrer's equation . Can some one suggest me that what may be the possible reason for decrease in the crystallite size ?
You can check this article;
J. Am. Ceram. Soc., 1–5 (2013) DOI: 10.1111/jace.
Hi,
I can think of a couple of reasons for this. (1) what is your substrate, and how thick are your films? It might be that you are seeing the effects of the thin film approaching 'bulk' characteristics following on from initial nucleation and the formation of a continuous thin film. (2) the sputtering process can impact film properties due to high energy reflected neutrals, this can result in atomic peening or argon ion incorporation, both effects can impact the structure and stress of a thin film. It might be worth seeing if these effects have been observed with other thin films with your measurement method.
Good luck and best regards,
Martin
Martin Goodchild Thaks for your response. The substrate used is sodalime glass .
You can check this article;
J. Am. Ceram. Soc., 1–5 (2013) DOI: 10.1111/jace.
There can be many reasons. Remember you are measuring an object that is not a completely random powder in the XRD sense. Films can be very tricky due to the presence of texture and residual stress .I would first check if the broadening is isotropic and if there is a change by changing the orientation of the film with respect to the scattering vector (so if stresses are present). The stress can influence the grain growth. I would also check if only size effects are present. I am pretty sure that if it is a problem of defects due to the sputtering, you can see it as microstrain. We have observed both texture gradients and stress gradients in RF magnetron sputtered film Check also that the production and measurement is done in the same point. there is a lack of uniformity between the film grown under the center of the target and the rims.. Last I would try to consider the whole pattern and not just the breadth of the peaks. Scherrer equation is nowadays obsolete.
Try using the TEM to confirm that your observations are accurate and correspond to the findings using Scherrer formular..
There are lots of reasons for decreasing of grain size during sintering ... such as temperature, time, change of grain growth mechanism...
However, I guess the main reason is zener pining.
Please see my published papers in
Advanced powder Technology, Powder metallurgy, materials characterization and ceramic international for better understanding zener pinning and grain growths mechanisms.
Regards
Mohammad Bagher Rahaei
- Badges
- Science topic
- Similar topics
- Philosophy
- Philosophy Of Science
- Reasoning