Fabrication and physical properties of bismuth layer-structured ferroelectric thin films with c-axis orientation epitaxially grown by high-temperature sputtering

Abstract

Highly c-axis oriented (Bi3.25Nd0.65Eu0.10)Ti3O12 (BNEuT) thin films were deposited on the Pt(100)/MgO(100) substrates by high-temperature sputtering. The substrate temperature was varied from 550 °C to 650 °C to examine its effect on the structural, dielectric, ferroelectric, and piezoelectric characteristics of the films, and consequently find the optimal substrate temperature for heteroepitaxial growth of BNEuT thin films. All the films deposited at 580 °C–650 °C exhibited a high degree of c-axis orientation [α(00l)] of ≥97%. All the films grown heteroepitaxially on Pt(100)/MgO(100) substrates was rotated by ±45° with respect to the underlying substrates and had a mainly upward polarization, based on data observed by piezoresponse force microscopy. Judging from the structural, dielectric, ferroelectric, and piezoelectric characteristics, it is shown that the optimal substrate temperature for heteroepitaxial growth of BNEuT films with a high α(00l) of >97% and a comparatively large remanent polarization of 2.0 μC cm−2 is 580 °C.

Effects of substrate temperature on physical properties of microrod-type multiferroic composite thin films fabricated by metal organic chemical vapor deposition

“…Secondly, the lattice constant is reduced due to volatilization of Bi, which has been confirmed in previous study. 28) Figure 3 shows the lattice spacing d calculated from the diffraction peak for BNEuT(001̲ 4̲ ) planes in composite films deposited at 450 °C−600 °C, and the Bi/Ti ratio in the MR structure. The d BNEuT(001̲ 4̲ ) decreased as the substrate temperature increased, but the Bi/Ti ratio remained almost constant.…”

“…21) In order to solve this problem and realize magnetic field−electric polarization control, we investigated the fabrication of c-axis oriented heteroepitaxial BNEuT films. 28) We also succeeded in a fabricating microrod (MR) structure in the fabricated thin film by reactive ion etching (RIE). 29) This structure makes it possible to achieve a large polarization along the a-axis, which is the in-plane polarization axis for c-axis oriented heteroepitaxial BNEuT films, so that a large ME effect can be expected.…”