**5. Conclusions**

Oriented NTO films were successfully deposited at 250 ◦C by ALD on various single crystalline substrates. All films had preferred orientations as deposited. Crystallinity improved after annealing at 650 ◦C for 15 min, but did not change the preferred orientations. On Al2O3(001), annealing led to cation ordering, and a change of symmetry from *R*−3*<sup>c</sup>* to *R*−3, visible by the appearance of the (003) and (009) reflections. However, the intensity was much lower, and the FWHM much larger, than for the other (00*l*) reflections, indicating that only parts of the film underwent cation ordering. AFM revealed very low rms roughnesses of about 0.2 nm, both for the as deposited and annealed film. The film||substrate epitaxial relationship was determined to be NTO(001)[100]||Al2O3(001)[100]. Depositions on LAO(100) resulted in films with two preferred orientations: NTO(*h*0*h*) and NTO(00*l*). There were no signs of ordering reflections for either orientation, indicating a *R*−3*<sup>c</sup>* symmetry. Annealing improved the crystallinity slightly, but did not alter the orientation of the film, the cation ordering nor change the rms roughness significantly, remaining at approximately 1 nm. Films deposited on STO(100) had a NTO(101)[220]||STO(100)010 epitaxial relationship with the substrate, with no signs or ordering reflections Annealing resulted in a slight improvement of crystallinity and increase in roughness, from 1.5 to 1.7 nm. Films deposited on MgO(100) had *R*−3*<sup>c</sup>* symmetry and the film||substrate epitaxial relationship was NTO(101)[220]||MgO(100)011. Reciprocal space mapping of the symmetrical NTO (202) reflection revealed a very small FWHM along *q*, indicating large crystallites in the film, and/or a very low tilt of the crystallites. No annealing was performed, but AFM investigations displayed larger crystallites protruding from a flatter surface, and the rms roughness was significantly larger than for films on other substrates, at 1.9 nm.

**Supplementary Materials:** Supplementary material is available online at http://www.mdpi.com/1996-1944/13/1/ 112/s1.

**Author Contributions:** Conceptualization, J.E.B., H.F. and O.N.; Data curation, J.E.B.; Formal analysis, J.E.B. and O.N.; Funding acquisition, H.F. and O.N.; Investigation, J.E.B.; Methodology, J.E.B. and O.N.; Project administration, H.F. and O.N.; Supervision, H.F. and O.N.; Validation, O.N.; Visualization, J.E.B.; Writing—original

draft, J.E.B. and O.N.; Writing—review and editing, J.E.B. and O.N. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by University of Oslo.

**Acknowledgments:** The authors would like to acknowledge Henrik Hovde Sønsteby and Øystein Slagtern Fjellvåg (University of Oslo) for help with obtaining RSMs and discussions in the related analysis, and the department of Geology (University of Oslo) for use of the XRF equipment.

**Conflicts of Interest:** The authors declare no conflict of interest.
