Research into 2‐dimensional materials has soared during the last couple of years. Next to van der Waals type 2D materials such as graphene and h‐BN, less well‐known oxidic 2D equivalents also exist. Most 2D oxide nanosheets are derived from layered metal oxide phases, although few 2D oxide phases can be also made by bottom‐up solution syntheses. Owing to the strong electrostatic interactions within layered metal oxide crystals, a chemical process is usually needed to delaminate them into their 2D constituents. This Review article provides an overview of the synthesis of oxide nanosheets, and methods to assemble them into nanocomposites, mono‐ or multilayer films. In particular, the use of Langmuir–Blodgett methods to form monolayer films over large surface areas, and the emerging use of ink jet printing to form patterned functional films is emphasized. The utilization of nanosheets in various areas of technology, for example, electronics, energy storage and tribology, is illustrated, with special focus on their use as seed layers for epitaxial growth of thin films, and as electrochemically active electrodes for supercapacitors and Li ion batteries.

Two-dimensional freestanding thin films of single crystalline oxide perovskites are expected to have great potential in integration of new features to the current Si-based technology. Here, we showed the ability to create freestanding single crystalline (011)- and (111)-oriented SrRuO3 thin films using Sr3Al2O6 water-sacrificial layer. The epitaxial Sr3Al2O6(011) and Sr3Al2O6(111) layers were realized on SrTiO3(011) and SrTiO3(111), respectively. Subsequently, SrRuO3 films were epitaxially grown on these sacrificial layers. The freestanding single crystalline SrRuO3(011)pc and SrRuO3(111)pc films were successfully transferred on Si substrates, demonstrating possibilities to transfer desirable oriented oxide perovskite films on Si and arbitrary substrates.

Vanadium dioxide (VO 2 ) is a much-discussed material for oxide electronics and neuromorphic computing applications. Here, heteroepitaxy of VO 2 is realized on top of oxide nanosheets that cover either the amorphous silicon dioxide surfaces of Si substrates or X-ray transparent silicon nitride membranes. The out-of-plane orientation of the VO 2 thin films is controlled at will between (011) M1 /(110) R and (−402) M1 /(002) R by coating the bulk substrates with Ti 0.87 O 2 and NbWO 6 nanosheets, respectively, prior to VO 2 growth. Temperature-dependent X-ray diffraction and automated crystal orientation mapping in microprobe transmission electron microscope mode (ACOM-TEM) characterize the high phase purity, the crystallographic and orientational properties of the VO 2 films. Transport measurements and soft X-ray absorption in transmission are used to probe the VO 2 metal-insulator transition, showing results of a quality equal to those from epitaxial films on bulk single-crystal substrates. Successful local manipulation of two different VO 2 orientations on a single substrate is demonstrated using VO 2 grown on lithographically patterned lines of Ti 0.87 O 2 and NbWO 6 nanosheets investigated by electron backscatter diffraction. Finally, the excellent suitability of these nanosheet-templated VO 2 films for advanced lensless imaging of the metalinsulator transition using coherent soft X-rays is discussed.

In order to integrate functional oxides with Complementary Metal Oxide Semiconductor (CMOS) materials, templates to ensure their epitaxial growth are needed. Although oxide nanosheets can be used to direct the thin film growth of transition metal oxides in a single out-of-plane orientation, the in-plane orientation of individual nanosheets within a nanosheet-based film is totally random. Here, we show the ability to improve the in-plane orientation of Ca2Nb3O10 nanosheets, and hence of SrRuO3 films grown on them by controlling their external shape. The parent-layered perovskite KCa2Nb3O10 particles were formed in square-like platelets, thanks to the anisotropic growth in molten K2SO4 salt, as opposed to the formation of irregular platelets in a solid-state reaction. The exfoliation of HCa2Nb3O10, which is the protonated form of KCa2Nb3O10, was optimized to retain the square-like shape of Ca2Nb3O10 nanosheets. Electron backscatter diffraction confirmed the improved in-plane orientation among square-like Ca2Nb3O10 nanosheets with the formation of larger SrRuO3 domains. As a result, SrRuO3 films showed the lower resistivity and higher residual resistivity ratio, ρ300K/ρ2K, on square-like Ca2Nb3O10 nanosheets than on irregularly shaped nanosheets of similar lateral nanosheet size.

To benefit from the diverse functionalities of perovskite oxides in silicon-based complementary metal oxide semiconductor (CMOS) technology, integrating oxides into a silicon platform has become one of the major tasks for oxide research. Using the deposition of LaMnO 3 /SrTiO 3 (STO) superlattices (SLs) as a case study, we demonstrate that (001) single oriented oxide SLs can be integrated on Si using various template techniques, including a single-layer buffer of STO prepared by molecular beam epitaxy (MBE) and pulsed laser deposition, a multilayer buffer of Y-stabilized zirconia/CeO 2 /LaNiO 3 /STO, and STO-coated two-dimensional nanosheets of Ca 2 Nb 3 O 10 (CNO) and reduced graphene oxide. The textured SL grown on STO-coated CNO nanosheets shows the highest crystallinity, owing to the small lattice mismatch between CNO and STO as well as less clamping from a Si substrate. The epitaxial SL grown on STO buffer prepared by MBE suffers the largest thermal strain, giving rise to a strongly suppressed saturation magnetization but an enhanced coercive field, as compared to the reference SL grown on an STO single crystal. These optional template techniques used for integrating oxides on Si are of significance to fulfill practical applications of oxide films in different fields.