STAFF

Hiroki MATSUO

Dr. Hiroki MATSUO

Research Fields
Ferroelectrics, Lattice defects, Domain engineering,  Pulsed-laser
deposition

Research interest

Ferroelectric materials have spontaneous electric polarization arising from a non-centrosymmetric crystal structure that can reversed by application of external electric field. Because of their characteristic polar structure, ferroelectric materials exhibit various functions such as piezoelectricity, pyroelectricity, electro-optic effect and anomalous photovoltaic effect, etc. Current research interest is the exploration of novel functions of the ferroelectric materials based on the following materials design strategies.

1.Ferroelectric artificial superlattice

A superlattice thin film has a periodic structure composed of thin layers of two or more materials. Because of an interfacial effect and a strong interaction between the layers, the superlattice sometimes exhibits unexpected property that is not predictable from the bulk properties of the constituting materials. The study aims to develop a ferroelectric thin-film capacitor that exhibits quite high energy density by exploiting the characteristic feature of the superlattice structure. For the fabrication of the ferroelectric superlattice, pulsed-laser deposition method with a reflection high energy electron diffraction system is used.

 

2.Ferroelectric photovoltaic effect

Ferroelectric materials exhibit characteristic photovoltaic responses owing to their polar crystal structure. While photovoltage generated by the conventional p-n junction of semiconductors is limited by bandgap energy of the materials, ferroelectric materials exhibit a high photovoltage exceeding the bandgap energy of them. We aim to enhance the photovoltaic response of the ferroelectric materials especially under visible light irradiation by chemical doping and by controlling ferroelectric domain structures.

 

3.Interaction between ferroelectric polarization and lattice defects

Charged lattice defects in the ferroelectric crystals strongly interact with the ferroelectric polarization through electrostatic and mechanical effects. The interaction enables control of the ferroelectric property by designing species, concentration, and distribution of the defects in the crystals. The goal of this study is to establish an effective approach to obtain desired ferroelectric properties by defect engineering.

Awards

The 18th JACG Best Presentation Awards
“Gap-State Engineering for Ferroelectric Photovoltaic Effect in BiFeO3 Epitaxial Thin Film”
Japanese Association for Crystal Growth (JACG). Dec. 13 2021.

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