Fabrication of Barium Titanate/Strontium Titanate Artificial Superlattice by Atomic Layer Epitaxy

Abstract

Epitaxial growth of BaTiO3, SrTiO3 and their superlattices was carried out by the alternating evaporation method using an atomic-layer-epitaxy control system for molecular beam epitaxy (MBE). Stable and reproducible control of the chemical composition was achieved by layer-by-layer growth with this system. Both BaTiO3 and SrTiO3 were grown epitaxially on SrTiO3 substrates, and clear oscillations of reflection high-energy electron diffraction (RHEED) intensity were observed, corresponding to the alternating depositions of BaO and TiO2 in BaTiO3 growth. The artificial superlattice with the structure of [(BaTiO3)5/(SrTiO3)5]7 was fabricated, and the X-ray diffraction (XRD) pattern of the superlattice was simulated by a step model. Diffraction angles of satellite peaks and the shape of Laue peaks in XRD patterns were consistent with those calculated, indicating that the designed structure was fabricated in the superlattice.

Cobalt Ferrite Nanocrystallites for Sustainable Hydrogen Production Application

“…Lowering the operating temperature for the O 2 generation step was an important step for the practical production of solar hydrogen. While the gas phase (Co, O 2 ) formation from CoO by the solar thermochemical process has been extensively studied [30,31], but that from the CoFe 2 O 4 phase has not yet been reported. In Figure 3(d), the amount of hydrogen production rate (L/hr) with time showed the stability of the system wherein the water-splitting conversion was totally depending upon product characteristics.…”

The Controlled Synthesis of Metastable Oxides Utilizing Epitaxy and Epitaxial Stabilization

“…192,193 Since that time it has been used to grow the oxide superconductors (Ba,K)BiO 3 , (Ba,Rb)BiO 3 , (La,Sr) 2 ; and superlattices of these phases. [4][5][6][7]76,79,110,119,124,157,199,[234][235][236][237] Although the use of MBE to grow functional oxides is much less mature than its use for compound semiconductors, examples included in this article show how the layering capabilities of MBE can control the composition profile of multicomponent functional oxides along the growth direction with subnanometer precision. This capability is relevant to the fabrication of epitaxial device structures and to the nanoengineering of new functional materials.…”

“…The maximum pressure depends on the MBE geometry, the element to be oxidized, and the oxidant species used, but oxidant pressures less than about 10 À4 Torr are typically required for MBE. 76 While molecular oxygen has been used for the growth of oxides that are easily oxidized, 79,157,192,193,[196][197][198][199][200][201][202][203][204][205][210][211][212][213][214][215]217,[222][223][224][225][226][227][228]232,[235][236][237] oxidants with higher activity are needed for the growth of ferroelectrics containing species that are more difficult to oxidize, e.g., bismuth-, lead-, or copper-containing oxides. For this purpose, purified ozone [4][5][6][7]76,79,110,112,114,117,119,203,[206][207][208]…”

Preparation and Size Control of Sodium Niobate Nanocube at Various Solvothermal Conditions

“…Such a polarization rotation was reported as mechanism of lead zirconium titanate having a morphotropic phase boundary [15][16][17], and it contributes to large dielectric and piezoelectric properties. On the basis of the interface-induced polarization rotation [5,23], we have been trying to prepare 3-dimentional artificial superlattice accumulation with different perovskite oxides in order to enhance electrical properties of materials. To prepare the 3-dimentional artificial superlattice accumulation, we propose nanocubes are used for constructing mosaic structure.…”