Molecular beam epitaxy of KTaO3

Abstract

Strain-engineering is a powerful means to tune the polar, structural, and electronic instabilities of incipient ferroelectrics. KTaO3 is near a polar instability and shows anisotropic superconductivity in electron-doped samples. Here, we demonstrate growth of high-quality KTaO3 thin films by molecular-beam epitaxy. Tantalum was provided by either a suboxide source emanating a TaO2 flux from Ta2O5 contained in a conventional effusion cell or an electron-beam-heated tantalum source. Excess potassium and a combination of ozone and oxygen (10% O3 + 90% O2) were simultaneously supplied with the TaO2 (or tantalum) molecular beams to grow the KTaO3 films. Laue fringes suggest that the films are smooth with an abrupt film/substrate interface. Cross-sectional scanning transmission electron microscopy does not show any extended defects and confirms that the films have an atomically abrupt interface with the substrate. Atomic force microscopy reveals atomic steps at the surface of the grown films. Reciprocal space mapping demonstrates that the films, when sufficiently thin, are coherently strained to the SrTiO3 (001) and GdScO3 (110) substrates.

Microscopic Insight into Structure Determination of Ferroelectric Photovoltaics in Aurivillius-Phase Ferroelectrics

“…16 The inside microstructure is dominated by the grain growth behavior, which generally affects the practical performance. 17 The emblematic microstructures of Sr 1−x Ba x Bi 4 Ti 4 O 15 (x = 0, 0.2, 0.5, 0.8, and 1.0) are shown in Figure 2a−e. Intriguingly, all the films showed dense morphologies and almost no obvious pores.…”

Leakage-Limitation Engineering Derived from an Interfacial Charge Barrier for Dielectric Energy Storage in Relaxation Ferroelectric Films

“…Therefore, the Na 0.5 Bi 3.25 La 1.25 Ti 4 O 15 /BaBi 3.4 La 0.6 Ti 4 O 15 composite film exhibits typical relaxation behavior, which is mostly attributable to the relaxation behaviors of the Na 0.5 Bi 3.25 La 1.25 Ti 4 O 15 layer and the BaBi 3.4 La 0.6 Ti 4 O 15 layer, as shown in Figure b,c. In addition, the generation of minor defects induces stress changes in certain regions of the lattice and charge imbalances, resulting in increased relaxation characteristics. ,, …”

Distinguishable Separation of Artificial Electron–Oxygen Vacancy Pairs Using Heterovalent Doping Effect for Ferroelectric Photovoltaics

“…This mismatch may lead to lattice strain and distortion, influencing crystal morphology and particle aggregation. Also, the local strain contributes to the surface energy and has significant influence on the morphology, which have been widely observed in oxide ferroelectrics. , It is important that the obvious grain shape evolution contributes to the ferroelectric polarization, where the grain shapes change from elliptical to dumbbell shapes in the doping films. This is caused by the anisotropic growth rate, and Mn presents an effective catalytic effect.…”