Surface dominant photoresponse of multiferroic BiFeO₃nanowires under sub-bandgap illumination

Abstract

A surface dominant sub-bandgap photo-carrier generation has been observed in multiferroic BiFeO3 (BFO) nanowires, which is mainly attributed to the depopulation of surface states that exist within the bandgap. Mapping of surface potential using Kelvin probe force microscopy (KPFM) further supports the depopulation of surface states in BFO nanowires under sub-bandgap illumination. The mechanism of photovoltage generation in BFO nanowires is investigated by measuring the photoresponse with local illumination of visible laser pulses at different positions of the BFO nanowires. Interestingly, large photovoltage signals were observed when the laser spot was focused close to contact electrodes, showing a position dependent effect of photoresponse in the BFO nanowires. The sub-bandgap excitation of surface states in multiferroic nanowires offers potential new strategies for application in photovoltaic devices.

Surface State‐Induced Anomalous Negative Thermal Quenching of Multiferroic BiFeO3 Nanowires

“…Multiferroic wide‐bandgap semiconductors, such as BiFeO 3 (BFO) have attracted intense research interests due to their broad range of potential applications in optoelectronic devices such as ferroelectric diodes, photovoltaic cells, photodetectors and photothermal sensing . In one dimensional (1‐D) BFO nanostructures, because of their high surface‐to‐volume ratio, surface states play a crucial role in their optical and electrical properties . The surface states may serve as traps for carriers and hence affect the recombination and transport of charge carriers .…”

“…[7] In one dimensional (1-D) BFO nanostructures, because of their high surface-to-volume ratio, surface states play a crucial role in their optical and electrical properties. [7][8][9][10] The surface states may serve as traps for carriers and hence affect the recombination and transport of charge carriers. [11][12][13] At the nanoscale, surface defect states are more dominant and are very sensitive to external stimuli such as photons, electric fields and temperature.…”

Advanced Characterization Methods for Electrical and Sensoric Components and Devices at the Micro and Nano Scales

“…The mechanism of photovoltage generation in BFO‐NWs was detected by local illumination of visible laser pulses at different positions of the BFO‐NWs and mapping of the photoresponse . Already a decade ago, Sadewasser et al proposed KPFM as a technique to probe the optoelectronic effect of Zn doping in polycrystalline CuInS 2 thin films implementing a local surface photovoltage spectroscopy (SPS).…”

Low-dimensional nanostructured photocatalysts

“…BFO nanowires with 50 nm in diameter and 5 μm in length were obtained when removing the template, revealing good photo induced oxidation ability. Many polycrystalline nanofiber metal oxide PCs were fabricated by electro spinning method, e.g., Bi 2 WO 6 [50], BFO [51], TiO 2 [52], and Bi 4 Ti 3 O 12 [53]. In the process of electro spinning, metal salts are dissolved in appropriate solvent stoichiometrically to form precursor sol, and polymers (e.g., PVP, PAN, PVB) are added to adjust the viscosity to a practicable value.…”