Two-Dimensional Perovskite Crystals Formed by Atomic Layer Deposition of CaTiO3 on γ-Al2O3

Abstract

CaTiO3 films with an average thickness of 0.5 nm were deposited onto γ-Al2O3 by Atomic Layer Deposition (ALD) and then characterized by a range of techniques, including X-ray Diffraction (XRD) and High-Resolution, Transmission Electron Microscopy (HRTEM). The results demonstrate that the films form two-dimensional crystallites over the entire surface. Lattice fringes from HRTEM indicate that the crystallites range in size from 5 to 20 nm and are oriented in various directions. Films of the same thickness on SiO2 remained amorphous, indicating that the support played a role in forming the crystallites.

A Study of How LaFeO3 and CaTiO3 Supports Affect the Oxidation, Hydrogenation, and Methane Steam Reforming Activity of Pt and Ni Catalysts

“…On the basis of the line width of the peak at 33° 2θ, the crystallite size of the perovskite phase was estimated to be between 9 and 11 nm. STEM/EDS images (Figures S1 and S2) show the La and Fe cover the support uniformly, and because the average thickness of the LaFeO 3 film for this sample was only 0.5 nm, the perovskite crystals must be two-dimensional, as demonstrated previously for other ALD-deposited perovskite films. , When compared with the JCPDS reference XRD pattern (no. 37-1493) for the LaFeO 3 phase, which is also included in Figure , the reflections for the perovskite film are shifted to slightly higher angles, ∼0.8°, suggesting that there is a small contraction of the crystal lattice in the film that did not change with oxidation or reduction.…”

“…Major problems include that (1) most perovskites have low surface areas, (2) the kinetics of metal exsolution are too slow at reasonable temperatures, and (3) some of the exsolved metal can remain embedded in the bulk and unavailable for reaction . Our groups have been working on a potential solution to these problems by preparing thin films of various mixed perovskites on inert supports using atomic layer deposition (ALD). − We have shown that using this approach one can produce two-dimensional, perovskite crystallites with lateral dimensions as large as 20 nm and thicknesses as thin as 0.5 nm. , Because a 0.5 nm film of LaFeO 3 on a 120 m 2 /g support corresponds to nearly 28 wt % LaFeO 3 , , such films will have sufficient capacity for taking up metal cations, but in contrast to bulk perovskite supports, the catalytic metals will remain at or near the surface.…”

Modulating Interactions between Molten Polystyrene and Porous Solids Using Atomic Layer Deposition

“…More importantly, the infiltration time saturates at ∼700 s after five cycles of ALD deposition, indicating that TiO 2 completely covers the SiO 2 surface. This result is consistent with our prior studies that showed that a complete layer of TiO 2 is formed after five cycles of ALD, as confirmed using transmission electron microscopy (TEM) and scanning TEM . The thickness of TiO 2 ALD after five cycles based on the growth rate of 0.7 Å/cycle is 0.35 nm, remarkably consistent with the previously reported value for a monolayer of the TiO 2 layer of 0.35 nm .…”

“…ALD is performed in a homebuilt, static system using procedures that have been described in detail (see the Supporting Information for details). ,,, The precursors for CaO, WO 3 , and TiO 2 are Ca­(TMHD) 2 (TMHD = 2,2,6,6-tetramethyl-3,5-heptanedionato), W­(CO) 6 , and TiCl 4 . (Note: CaO converts to CaCO 3 in the presence of CO 2 …”

Excellent Bipolar Resistive Switching Characteristics of Bi4Ti3O12 Thin Films Prepared via Sol-Gel Process

“…In recent years, breakthroughs have been made in film synthesis technology. Many physical and chemical methods have been used to synthesize films, such as atomic layer deposition (ALD) [23], sol-gel method [24], and metalorganic chemical vapor deposition (MOCVD) [25]. Among them, the sol-gel method has been widely used due to its advantageous large-area uniformity, simple equipment, and relatively low processing temperature.…”