Ultralow thermal conductivity of turbostratically disordered MoSe ultra-thin films and implications for heterostructures.

Films containing 8, 16, 24, 32 and 64 MoSe layers were synthesized using the modulated elemental reactants method. X-ray reflectivity patterns showed that the annealed films were the targeted number of MoSe layers thick with atomically smooth interfaces. In-plane x-ray diffraction (XRD) scans contained only hk0 reflections for crystalline MoSe monolayers.

Charge transfer in (PbSe) (NbSe) and (SnSe) (NbSe) ferecrystals investigated by photoelectron spectroscopy.

Rotationally disordered, layered (PbSe)[Formula: see text](NbSe) and (SnSe)[Formula: see text](NbSe) ferecrystal heterostructures, consisting of stacked two-dimensional bilayers of either PbSe or SnSe alternating with two planes of NbSe, were synthesized from modulated elemental reactants. The electronic structure of these ternary systems was investigated using x-ray photoelectron spectroscopy and compared to the binary bulk compounds PbSe, SnSe and NbSe. The Pb and Sn core level spectra show a significant shift towards lower binding energies and the peak shape becomes asymmetric in the ferecrystals, while the electronic structure of the NbSe layers does not change compared to the bulk.

Interface-Driven Structural Distortions and Composition Segregation in Two-Dimensional Heterostructures.

The discovery of emergent phenomena in 2D materials has sparked substantial research efforts in the materials community. A significant experimental challenge for this field is exerting atomistic control over the structure and composition of the constituent 2D layers and understanding how the interactions between layers drive both structure and properties. While no segregation for single bilayers was observed, segregation of Pb to the surface of three bilayer thick PbSe-SnSe alloy layers was discovered within [(Pb Sn Se) ] (TiSe ) heterostructures using electron microscopy.

Long-Range Order in [(SnSe)][TiSe] Prepared from Designed Precursors.

Self-assembly of designed precursors has enabled the synthesis of novel heterostructures that exhibit extensive rotational disorder between constituents. In (SnSe)TiSe nanoscale regions of long-range order were observed in scanning transmission electron microscopy (STEM) cross sectional images. Here a combination of techniques are used to determine the structure of this compound, and the information is used to infer the origin of the order.

Amorphous Mixed-Metal Oxide Thin Films from Aqueous Solution Precursors with Near-Atomic Smoothness.

Thin films with tunable and homogeneous composition are required for many applications. We report the synthesis and characterization of a new class of compositionally homogeneous thin films that are amorphous solid solutions of AlO and transition metal oxides (TMO) including VO, CrO, MnO, FeO, CoO, NiO, CuO, and ZnO. The synthesis is enabled by the rapid decomposition of molecular transition-metal nitrates TM(NO) at low temperature along with precondensed oligomeric Al(OH)(NO) cluster species, both of which can be processed from aq solution.

Structural Changes in 2D BiSe Bilayers as n Increases in (BiSe)(NbSe) (n = 1-4) Heterostructures.

(BiSe)(NbSe) heterostructures with n = 1-4 were synthesized using modulated elemental reactants. The BiSe bilayer structure changed from a rectangular basal plane with n = 1 to a square basal plane for n = 2-4. The BiSe in-plane structure was also influenced by small changes in the structure of the precursor, without significantly changing the out-of-plane diffraction pattern or value of the misfit parameter, δ.

Antiphase Boundaries in the Turbostratically Disordered Misfit Compound (BiSe)(1+δ)NbSe2.

(BiSe)(1+δ)NbSe2 ferecrystals were synthesized in order to determine whether structural modulation in BiSe layers, characterized by periodic antiphase boundaries and Bi-Bi bonding, occurs. Specular X-ray diffraction revealed the formation of the desired compound with a c-axis lattice parameter of 1.21 nm from precursors with a range of initial compositions and initial periodicities.