Author(s) Gardner, J.; Thakre, A.; Kumar, A.; Scott, J.F.
Journal Rep Prog Phys
Date Published 2019 Sep
Abstract

We review all the published literature and show that there is no experimental evidence for homogeneous tin titanate SnTiO in bulk or thin-film form. Instead a combination of unrelated artefacts are easily misinterpreted. The x-ray Bragg data are contaminated by double scattering from the Si substrate, giving a strong line at the 2θ angle exactly where perovskite SnTiO should appear. The strong dielectric divergence near 560 K is irreversible and arises from oxygen site detrapping, accompanied by Warburg/Randles interfacial anomalies. The small (4 µC cm) apparent ferroelectric hysteresis remains in samples shown to be pure (Sn,Ti)O rutile/cassiterite, in which ferroelectricity is forbidden. Only very recent work reveals real bulk SnTiO, but it possesses an ilmenite-like structure with an elaborate array of stacking faults, not suitable for ferroelectric devices. Unpublished TEM data reveal an inhomogeneous SnO layered structured thin films, related to shell-core structures. The harsh conclusion is that there is a combination of unrelated artefacts masquerading as ferroelectricity in powders and ALD films; and only a trace of a second phase in PLD film data suggests any perovskite content at all. The fact that x-ray, dielectric, and hysteresis data all lead to the wrong conclusion is instructive and reminds us of earlier work on copper calcium titanate (a well-known boundary-layer capacitor).

DOI 10.1088/1361-6633/ab37d4
ISSN 1361-6633
Citation Rep Prog Phys. 2019;82(9):092501.

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