I have deposited Cr2AlC MAX phases on a Nickel substrate and found a decrease in average crystal size with the increase in sputtering power. The sputtering powers are really high between (1-5 KW). A DC mode is used for the sputtering purpose and Schrrer Equation has been used for the calculation of crystal size. Literature indicates that an increase in sputtering powers leads to increase in crystal size . The sputtering powers are generally low in such papers: 100W-500W. Please let me know if I am doing any mistakes during the calculation or this can really be an effect at very high sputtering powers.
Please let me know about possible citations through which I can supoort my arguments.
Thanks
I am not a specialist in this task, but I would believe that if I increase the sputter power I will increase the number of particles bombarding the surface. Possibly These high flow of particles may have an etching effect on the growing crystals, so they will not increase but decrease in size. Probably that will also depend on the energy of particles, i.e. target voltage used during sputtering.
I am also not an expert of this field, however in my opinion the Scherrer equation is not really suitable for this case, as you definitely have plenty of crystal defects and macrostrain in the deposited system for which the this equation cannot account. These also give considerable peak broadening (though usually in the higher order reflections), which leads to smaller apparent crystallite size by using the Scherrer eq.
I would suggest to use something more advanced method. As a first guess Williamson--Hall would be a better choice (there at least you would be able to separate size and strain effects), but of course some full profile analysis method would be even better.
Thank you very much Dr. Schiffmann and Dr. Hegedus for the information. I would keep the above mentioned factors for further investigations.
In order to fully understand the effect of the sputtering process on the microstructure of your thin film, it would be helpful to measure the current and energies of bombarding particles during growth. For large ratios of bombarding particles (from the sputtering gas) over deposited particles you end up with a large density of crystal defects, and even fully amorphous films can be produced by this. Next to the references given below, valuable information can be found in E.S. Machlin: The Relationship Between Thin Film Processing and Structure, Giro, Croton-on-Hudson, 1995.
Article X ray diffraction study on residual stress and preferred ori...
Book Thin Film Analysis by X-ray Scattering
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