Bulk photovoltaic effects in Mn-doped BiFeO 3 thin films and the optical strains

Pt/1-µm-thick Bi 1.0 Fe 0.99 Mn 0.01 O 3 (BFMO)/Pt coplanar capacitors with an interelectrode distance of 260 µm have been fabricated on vicinal SrTiO 3 (STO) (001) substrates by radio frequency magnetron sputtering. The bulk photovoltaic effect of a BFMO thin film has been investigated by measuring the current–voltage ( I – V ) characteristics of the Pt/BFMO/Pt coplanar capacitors under blue-violet laser illumination (λ = 405 nm). The I – V characteristics show the light-polarization-dependent open-circuit voltage ( V OC ) with a maximum of −209 V. In addition, the optical strain of a BFMO/STO cantilever with a size of 15 mm × 1.3 mm × 70 µm has been investigated by measuring the displacement of the edge of the cantilever under blue-violet laser illumination. The edge displacement depended on light polarization, indicating that the optical strain is due to the coupling between the bulk photovoltaic effect and the inverse piezoelectric effect.