Taking
advantage of strain engineering, Nd2WO6 (NdWO)
thin films have been successfully grown on (001)-oriented
SrTiO3 single-crystal substrates by pulsed-laser deposition.
High-resolution X-ray diffraction characterizations highlight the
stabilization of a new orthorhombic (Pm21
n) NdWO polymorphic form, isostructural to α-La2WO6. Reciprocal space mappings have been used in
the determination of the NdWO thin-film structure. Coupled with the
2θ-ω X-ray patterns, the cell parameters were calculated: a = 16.34(5) Å, b = 5.46(5) Å,
and c = 8.68(1) Å. X-ray-diffraction pole-figure
measurements show the crystallographic relationships between the film
and substrate: [100]NdWO∥[110]STO, [010]NdWO∥[11̅0]STO, and [001]NdWO∥[001]STO. Both X-ray diffraction and transmission
electron microscopy studies reveal the existence of (510)-oriented
crystallites with respect to the plane of the substrate mainly at
the interface film/substrate and dispersed in the (001)-NdWO matrix.
In addition, robust piezoelectricity and ferroelectricity are revealed
at room temperature through both local hysteresis loops and domain
manipulation experiments using the piezoresponse force microscopy
technique. Typical polarization retention behaviors associated with
specific nanoscale conduction are in good agreement with the classical
ferroelectric phenomenon in oxide materials. The successful observation
of piezo-/ferroelectricity at room temperature in innovative strain-stabilized
α-NdWO thin films paves the way for new lead-free functional
materials devoted to numerous applications, including actuators, sensors,
or nonvolatile memory devices.