Dynamic Control of Piezoelectricity Enhancement via Modulation of the Bulk Photovoltaic Effect in a BiFeO3 Thin Film

Piezoelectricity, which is an electromechanical effect induced by conversion between mechanical and electrical energy, is one of the key functionalities in ferroelectric oxides. Traditionally, structural engineering in synthesis via a variety of processing control parameters has been a well-established route to host so-called morphotropic phase boundaries for enhancing piezoelectricity. However, this involves dealing with synthetical complexity and difficulties of strictly controlling structures and defects. Instead, for simple and in situ control, here, a critical pathway for light-induced piezoelectricity enhancement and its dynamic control is unveiled in a BiFeO3/DyScO3 thin film by implementing an in-plane geometry operation, allowing for modulation of the bulk photovoltaic effect. A series of in-plane length-dependent piezoresponse force microscopy and conductive atomic force microscopy-based measurements under illumination reveals its strong influence on the photocurrent and photovoltage, consequently revealing a maximum of eightfold increase of the effective piezoelectric coefficient, d(zz). Light polarization dependent measurements show sinusoidal behavior of piezoelectricity closely linked to photocurrent variations, leading to a further threefold increase of d(zz). Temporal decay measurements reveal persistent behavior of enhanced piezoelectricity after removal of illumination, associated with reemission of photocarriers trapped in sub-levels. These results pave the way for light-induced piezoelectricity enhancement compatible with the photovoltaic effect in ferroelectric thin films for multifunctional nano-optoelectronics.