Hierarchical dielectric orders in layered ferroelectrics Bi2SiO5.

Younghun Kim,Jungeun Kim,Sungwng Kim,Akihiko Fujiwara,Hideo Hosono,Kunihisa Sugimoto,Kenichi Kato,Hiroki Taniguchi,Hiroshi Tanaka,Mitsuru Itoh,Masaki Takata

doi:10.1107/s2052252514008008

Abstract

Electric dipole engineering is now an emerging technology for high electron-mobility transistors, ferroelectric random access memory and multiferroic devices etc. Although various studies to provide insight into dipole moment behaviour, such as phase transition, order and disorder states, have been reported, macroscopic spontaneous polarization has been mainly discussed so far. Here, visualization of the electric dipole arrangement in layered ferroelectrics Bi2SiO5 by means of combined analysis of maximum entropy charge density and electrostatic potential distribution analysis based on synchrotron radiation X-ray powder diffraction data is reported. It was found that the hierarchical dipole orders, the weak-ferroelectric and ferroelectric configurations, were observed in the Bi2O2 and the SiO3 layers, respectively, and the ferrielectric configuration was realised by the interlayer interaction. This discovery provides a new method to visualize the local polarization in ferroelectric materials.

Highlights

Designing and controlling the intense local electric field and/ or polarization in solids is vital for emerging electronics, such as high-performance field-effect transistors, ferroelectric random access memory and multiferroic devices in the nanoscale
Electrostatic potential (EP) analysis based on electron charge density (ECD) using the maximum entropy method (MEM) has been developed for the characterization of specific features originating from the electrostatic field/force on the microscopic scale (Sakata & Sato, 1990; Takata & Sakata, 1996; Takata, 2008; Tanaka et al, 2006; Kim et al, 2011)
We report the visualization of the electric dipole arrangement in layered ferroelectrics Bi2SiO5 by means of combined analysis of the ECD using MEM and EP distribution analysis based on high-precision synchrotron radiation X-ray powder diffraction data

Summary

Introduction

Designing and controlling the intense local electric field and/ or polarization in solids is vital for emerging electronics, such as high-performance field-effect transistors, ferroelectric random access memory and multiferroic devices in the nanoscale (de Araujo et al, 1995; Auciello et al, 1998; Haertling, 1999; Scott, 2000; Dawber et al, 2005; Schilling et al, 2007; Chung et al, 2011; Yamada et al, 2012; Keeney et al, 2012a,b, 2013; Maity et al, 2012; Zhang et al, 2012). Electrostatic potential (EP) analysis based on electron charge density (ECD) using the maximum entropy method (MEM) has been developed for the characterization of specific features originating from the electrostatic field/force on the microscopic scale (Sakata & Sato, 1990; Takata & Sakata, 1996; Takata, 2008; Tanaka et al, 2006; Kim et al, 2011). The polarization of BSO is suggested to originate from the SiO3 layer and not from the Bi2O2 layer by the firstprinciples calculations (Taniguchi et al, 2013). We report the visualization of the electric dipole arrangement in layered ferroelectrics Bi2SiO5 by means of combined analysis of the ECD using MEM and EP distribution analysis based on high-precision synchrotron radiation X-ray powder diffraction data

Experimental

Results

Summary