Microstructure and local electrical investigation of lead-free α-La2WO6 ferroelectric thin films by piezoresponse force microscopy

La2WO6 (LWO) thin films with the α high-temperature orthorhombic polymorph have been grown on (001)-LaAlO3 (LAO) substrates by pulsed laser deposition. The X-ray diffraction study evidences that the films are (00l)-oriented. This matching appears to be in good agreement with the compatibility between the α-LWO bulk/LAO substrate crystal lattices. Pole figure measurements lead to the following crystallographic relationships between the film and substrate: [100]α-LWO║ [110]LAO, [010]α-LWO ║ [11-0]LAO and [001]α-LWO ║ [001]LAO. Film cell parameters measured on a LaNiO3 buffer layer, setting as electrode for electric measurements, lead to a = 16.217(5) Å, b = 5.607(1) Å and c = 8.918(8) Å. A Williamson-Hall plot carried out on a LWO film reveals that the microstrain is 0.16% along the growth direction while the coherent domain dimension is 16 nm. Piezoresponse force microscopy imaging and piezoloops recording demonstrate that these films are piezoelectric/ferroelectric on nanoscale.