Epitaxial multilayers of alkanes on two-dimensional black phosphorus as passivating and electrically insulating nanostructures

Mechanically exfoliated 2D black phosphorus and solution casted tetracosane form a semiconductor/insulator, stable van der Waals heterostructure.

CADEM: calculate X-ray diffraction of epitaxial multilayers

Epitaxial multilayers and superlattice (SL) structures are gaining increasing importance as they offer the opportunity to create artificial crystals with new functionalities. These crystals deviate from the parent bulk compounds not only in terms of the lattice constants but also in the symmetry classification, which renders calculation of their X-ray diffraction (XRD) patterns tedious. Nevertheless, XRD is essential to get information on the multilayer/SL structure such as, for example, out-of-plane lattice constants, strain relaxation and period length of the crystalline SL. This article presents a powerful yet simple program, based on the general one-dimensional kinematic X-ray diffraction theory, which calculates the XRD patterns of tailor-made multilayers and thus enables quantitative comparison of measured and calculated XRD data. As the multilayers are constructed layer by layer, the final material stack can be entirely arbitrary. Moreover, CADEM is very flexible and can be straightforwardly adapted to any material system. The source code of CADEM is available as supporting material for this article.

Analysis of Ferromagnetic-Multiferroic Interfaces in Epitaxial Multilayers of LSMO and BFO

Bilayers were fabricated from ferromagnetic LSMO (Lanthanum Strontium Manganate Oxide, La0.7Sr0.3MnO3) and ferroelectric BFO (Bismuth Ferrite, BiFeO3) using pulsed laser deposition in the presence of O2 on LaAlO3and SrTiO3 substrates. The layer thickness and the layer order were varied among 16 samples. The bilayers were analyzed using TEM, XRD, XRR, and XPS to determine the stoichiometry, interlayer diffusion, roughness, and other structural features. TEM imaging showed that portions of the bilayers were highly crystalline. However, XRD analysis demonstrated that the majority of films were amorphous, with some polycrystalline and nanocrystalline samples. XRR data indicated a high roughness but did not yield good thickness values. Finally, XPS confirmed that material stoichiometry was preserved. It appears that the deposition process still needs optimization. This research will serve as the basis for future experiments on the magnetic properties of LSMO/BFO bilayers.