I have sputtered the SrFe12O19 using ceramic target in Ar atmosphere (Ar = 100%) and then in Ar+O2 atmosphere (Ar = 99% and O2 = 1%). The orientation of the SrM planes observed in the XRD patterns for the condition when O2 is introduced is stronger as compared to pure Ar atmospheric condition.
Oxygen forms negatively charged ions in a plasma, in contrast to argon that only forms positively charged ions. Negatively charged ions are accelerated towards your substrate and bombard it. This can change the film stoichiometry and generally lead to resputtering effects, like for example film texture. You may try PLD or high-pressure oxygen sputtering if you want to grow films under oxidizing conditions.
Sputtering is a technique that does not trivially give stoichiometric nature. In order to make stoichiometric oxide films, especially such as perovskites by sputtering, you will have to use an oxygen background. This stoichiometry could be playing the important role in generating the crystal structure that you want. In the case of oxygen deficiency, there can be local changes in the oxidation states of the transition metal atoms and lead to distortion of the crystal structure. Since such distortions could be avoided by maitaining good stoichiometry, you might be getting good xrd patterns.
Oxygen forms negatively charged ions in a plasma, in contrast to argon that only forms positively charged ions. Negatively charged ions are accelerated towards your substrate and bombard it. This can change the film stoichiometry and generally lead to resputtering effects, like for example film texture. You may try PLD or high-pressure oxygen sputtering if you want to grow films under oxidizing conditions.
The oxygen has an important role during the deposition, mianly in PLD method. The oxygen pressure can govern not only the preferential orientation, but also the crystallization and microstructure of the thin films.
In relation to the microstructure you can read about Thornton Structure Zone Model that attribute the change of the morphology of thin films to the properties of the species appearing on the surface substrate.
During the deposition, these ablated species lose their kinetic energy when they are ejected from the target and this is specially due to scattering by the oxygen molecules. If you have high oxygen pressure, the species reach the substrate with a lower kinetic energy and their surface mobility decreases leading the formation of smalls size with one main orientation. So, increase the oxygen pressure in Ar+O2 atmosphere to have well crystallized and oriented thin film.
To help you see these two two papers of John A. Thornton.
Thank you all for your kind support, suggestion and perticularly your exptertise views.
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