Atomic layer epitaxy of Ruddlesden-Popper SrO(SrTiO3)n films by means of metalorganic aerosol deposition

Abstract

We report an atomic layer epitaxial growth of Ruddlesden-Popper (RP) thin films of SrO(SrTiO3)n (n = ∞, 2, 3, 4) by means of metalorganic aerosol deposition (MAD). The films are grown on SrTiO3(001) substrates by means of a sequential deposition of Sr-O/Ti-O2 atomic monolayers, monitored in-situ by optical ellipsometry. X-ray diffraction and transmission electron microscopy (TEM) reveal the RP structure with n = 2–4 in accordance with the growth recipe. RP defects, observed by TEM in a good correlation with the in-situ ellipsometry, mainly result from the excess of SrO. Being maximal at the film/substrate interface, the SrO excess rapidly decreases and saturates after 5–6 repetitions of the SrO(SrTiO3)4 block at the level of 2.4%. This identifies the SrTiO3 substrate surface as a source of RP defects under oxidizing conditions within MAD. Advantages and limitations of MAD as a solution-based and vacuum-free chemical deposition route were discussed in comparison with molecular beam epitaxy.

Fine Structure in Multi-Phase Zr8Ni21-Zr7Ni10-Zr2Ni7 Alloy Revealed by Transmission Electron Microscope

“…A SAED pattern forms a region with a lower density of defects in Figure 6b and shows that it can be indexed as Zr 2 Ni 7 in the [110] zone axis, which is confirmed by comparing it with the simulated [110] patterns, Figure 6e, using a structural model of Eshelman et al . [24]. However, SAED from regions with a higher density of defects, Figure 6b, shows a dense distribution of reflection and intensity streaks along the 0 kl rows.…”

“…These variations can be understood as the following: according to the structural model of Eshelman [24], the structural blocks shown in Figure 7a are very similar but not identical, thus the periodicity c = 1.2193 nm. In the analysis by Parthe and Lemair [33], by allowing small changes in the point positions of less than 0.5 nm, a unit-cell transformation can be made which leads to a smaller monoclinic unit cell with c = 0.6307 nm.…”

“…Projection of the Zr 2 Ni 7 structure in the [100] direction for a structural model of Eshelman [24] and Parthe [27] ( a ), a projection of the layers from ( a ) with an outlined pseudo-hexagonal unit cell ( b ) and simulated SAED patterns with the electron beam’s direction normal to the layers’ planes (ZA = [0.24 0 0.9]) for very thin (1 nm) ( c ) and thicker (10 nm) ( d ) Zr 2 Ni 7 crystals.…”

“…Transmission Electron Microscopy (TEM) applied together with other chemical-sensitive techniques (EDS, electron energy-loss spectroscopy, etc .) is capable of providing both structural and chemical information at the sub-atomic level [24,25,26]. Crystal structure, chemical composition, or atomic bonding can be easily characterized [27,28,29].…”

Magneto-dielectric effect in relaxor superparaelectric Tb2CoMnO6 film

“…Here we report the epitaxial growth of monoclinic Tb2CoMnO6/Nb:SrTiO3(100) thin film by using a metalorganic aerosol deposition (MAD) technique 21 . The established partial B-site disorder in the film is accompanied by a short range ordering of spins as manifested by the deviation from a standard Curie-Weiss law at T*~190 K, i.e.…”