Interplay of negative electronic compressibility and capacitance enhancement in lightly-doped metal oxide Bi0.95La0.05FeO3 by quantum capacitance model

S Nathabumroong,B Yotburut,R Yimnirun,S.-K Mo,S Siriroj,T Eknapakul,T Saisopa,R Supruangnet,H Nakajima,W Meevasana,P Jaiban,S Maensiri

doi:10.1038/s41598-020-61859-6

Abstract

Light-sensitive capacitance variation of Bi0.95La0.05FeO3 (BLFO) ceramics has been studied under violet to UV irradiation. The reversible capacitance enhancement up to 21% under 405 nm violet laser irradiation has been observed, suggesting a possible degree of freedom to dynamically control this in high dielectric materials for light-sensitive capacitance applications. By using ultraviolet photoemission spectroscopy (UPS), we show here that exposure of BLFO surfaces to UV light induces a counterintuitive shift of the O2p valence state to lower binding energy of up to 243 meV which is a direct signature of negative electronic compressibility (NEC). A decrease of BLFO electrical resistance agrees strongly with the UPS data suggesting the creation of a thin conductive layer on its insulating bulk under light irradiation. By exploiting the quantum capacitance model, we find that the negative quantum capacitance due to this NEC effect plays an important role in this capacitance enhancement

Highlights

Light-sensitive capacitance variation of Bi0.95La0.05FeO3 (BLFO) ceramics has been studied under violet to UV irradiation
The experimentally-observed changes indicate that the quantum capacitance model plays a major role, which supports claims for a strong interplay between negative electronic compressibility (NEC) and capacitance enhancement
We chose BLFO because of its high initial capacitance, for example, its dielectric constant was more than three times that of pure BiFeO3 ceramics prepared by the same method[9,14,28]

Summary

Introduction

Light-sensitive capacitance variation of Bi0.95La0.05FeO3 (BLFO) ceramics has been studied under violet to UV irradiation. Efforts to improve the dielectric behavior of BiFeO3 have been reported, such as varying preparation methods[12] and dopants[13] Such extrinsic dielectric constant enhancement can be controlled by lattice distortions, particle sizes, domains, or impurities[12,14]. The capacitance enhancement induced by surface charge accumulation has been reported on CaCu3Ti4O1226 This is similar to the case of applying electric field The experimentally-observed changes indicate that the quantum capacitance model plays a major role, which supports claims for a strong interplay between NEC and capacitance enhancement. These findings are critical in understanding the fundamental nature of such system as well as establishing a new synthetic route to light-sensitive capacitive devices

Methods

Results

Conclusion