We have demonstrated pressure-induced transition in a c-axis oriented V2O3 thin film from strongly correlated metal to Mott insulator in a submicrometric region by inducing a local stress using contact atomic force microscopy. To have an access to a pressure range of sub-gigapascal, a tip with a large radius of 335 nm was prepared by chemical vapour deposition of platinum onto a commercial tip with a focused ion beam (FIB). The FIB-modified tip gives a good electrical contact at low working pressures (0.25-0.4 GPa) allowing unambiguously to evidence reversible metalinsulator transition in a pulsed laser-deposited V2O3 thin film by means of local investigations of current-voltage characteristics. A finite element method has confirmed that the diminution of c/a ratio under this tip pressure explains the observed phase transition of the electron density of states in the film.

We prepared a stacked structure consisting of a quasi-free-standing functional oxide thin film and a ceramic piezoelectric disk and observed the effect of the piezoelectric disk deformation on the resistance of the thin film. Epitaxial V 2 O 3 films were grown by a pulsed laser deposition method on muscovite mica substrates, peeled off using Scotch tapes, and transferred onto piezoelectric elements. In this V 2 O 3 /insulator/top electrode/piezoelectronic disk/bottom electrode structure, the resistance of the V 2 O 3 film displayed a variation of 60% by sweeping the piezoelectronic disk bias. With support from x-ray diffraction measurements under an electric field, a huge gauge factor of 3 × 10 3 in the V 2 O 3 film was inferred. The sizeable resistance change in the V 2 O 3 layer is ascribed to the piezo-actuated evolution of c/a ratios, which drives the material towards an insulating phase. A memory effect on the resistance, related to the hysteretic displacement of the piezoelectric material, is also presented.

The piezoelectric properties of compositional spread (1 À x)BiFeO 3 -xGaFeO 3 epitaxial thin films are investigated where Ga 3þ substitution for Bi 3þ is attempted in Bi 1Àx Ga x FeO 3 compounds. Ga content x was varied from 0 to 12% (atomic). Ferroelectric characterizations are reported at various length scales. Around 6.5% of Ga content, an enhancement of the effective piezoelectric coefficient d eff 33 is observed together with a change of symmetry of the film. Measured d eff 33 values in 135 nm thick films increased from 25 pm/V for undoped BiFeO 3 to 55 pm/V for 6.5% Ga with no extrinsic contribution from ferroelastic domain rearrangement. V

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