Dresden 2014 – scientific programme
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DF: Fachverband Dielektrische Festkörper
DF 18: Dielectric and ferroelectric thin films
DF 18.5: Talk
Wednesday, April 2, 2014, 17:20–17:40, GER 37
Photo-electronic processes in BiFeO3 — •Akash Bhatnagar1, Young Heon Kim2, Dietrich Hesse1, and Marin Alexe1,3 — 1Max Planck Institute of Microstructure Physics, D-06120 Halle, Germany — 2Korea Research Institute of Standards and Science, Daejeon 305-304, Rep. of Korea — 3University of Warwick, Department of Physics, Coventry CV8 2EN, United Kingdom
Recently, reports regarding the observation of above-band gap open-circuit voltages (Voc) in BiFeO3 (BFO) thin films under illumination, i.e. the photovoltaic effect (PV), has attracted much attention in the field of ferroelectric materials. Initial investigations primarily attributed this effect to charge separation at ferroelastic domain walls . Subsequent studies, via localized measurements, revealed the presence of shallow trap levels which might be contributing towards the effect . Thus till now, the origin of this effect has been under some clouds of speculations.
In the present work we have elaborated upon conclusive evidence to determine the actual role of domain walls in the PV effect. Moreover, an analytical model will be presented via which the generation of PV current in different directions can be calculated. By performing temperature dependent and angle resolved measurements we prove that the bulk photo effect, which has been at the origin of the PV effect in other ferroelectric materials, is also responsible in case of BFO. However, the presence of ferroelastic domains and domain walls largely influences its manifestation. Similar measurements performed on strained BFO provide an insight into different conduction mechanisms.