Optical, electrical and photoelectric properties of layered-perovskite ferroelectric Bi2WO6 crystals

Abstract

Ferroelectric perovskites have attracted extensive attention recently, because of their fascinating physical properties and novel characteristics owing to the coupling of electric polarization with other functional properties. Herein, single crystals of a bismuth layered-perovskite ferroelectric oxide Bi₂WO₆ (BWO) were grown by a flux growth method. The grown crystals exhibit platelet morphology with a dominant (001) orientation face. The linear and nonlinear optical properties of BWO crystals were studied in detail. The optical transmittance spectrum shows that BWO is a direct transition semiconductor with a band gap of 2.75 eV and a wide transmission window up to 5 μm. Second harmonic generation (SHG) measurements indicate that the crystal is also a phase matchable nonlinear optical material with a large SHG response of approximately 2.1 times that of KH₂PO₄. The dielectric and ferroelectric properties measured perpendicular to the ab plane exhibit an oxygen vacancy associated dielectric loss peak and a non-ferroelectric P–E loop. Moreover, we found that the BWO crystal possesses a significant photoresponse in the broadband wavelength of visible light, showing fast response (<0.1 s), high ON/OFF current ratio (>10³), excellent flexibility and robustness. The origin of physical properties was interpreted on the basis of the crystal structure combined with density functional theory (DFT) calculations. The BWO single crystals with large SHG response, rich electrical behavior and broad spectral photoresponse are promising materials for nonlinear optical, electrical and optoelectronic applications.