Surface science studies of two-dimensional Ba–Ti–O films on Pd(111) identify three different small unit cell structures (see article number 2100389 by Stefan Förster and co-workers). In scanning tunneling microscopy these structures exhibit an atomic base of four atoms of one species, decorating the vertices of two triangles. As depicted on the cover, this base rearranges upon atomic density variations. In a fully stretched-out fashion (left side), corresponding to the lowest density state, a square lattice is formed. In the high-density limit (right side) a rectangular structure forms, in which rhombuses fill the gaps. The medium density motif incorporates squares and rhombuses.

MXY (M = W, Mo; X, Y = S, Se, Te) Janus monolayers are noncentrosymmetric systems with strong spin–orbit coupling effects, giving rise to interesting physical phenomena. By using the full-potential linearized augmented plane-wave method (FP-LAPW), Daniel Olguín and co-workers study the electronic properties of the MoXY (X, Y = S, Se, Te) Janus monolayers (see article number 2100248). These Janus monolayers are found to present a spin polarization near the high symmetry Γ, K_–, and K₊ points of the valence band. Among the studied systems, MoSeTe and MoSSe present spin–valley polarization, Rashba spin-splitting, and a direct bandgap, representing an interesting atomically thin material that can be exploited in different applications such as spintronics, spin-orbitronics, and nanoelectronics.

Band offset parameters in FeNiO/CuNiO bilayer film are obtained using X-ray photoelectron spectroscopy and ultraviolet–visible spectroscopy. From valence band maxima and core level energy positions, the valence band and conduction band offsets are estimated to be 0.8 eV and 0.3 eV, respectively. A type-I band alignment is identified at the interface of the grown bilayer film.

CaRuO₃ with a perovskite ABO₃ structure has attracted considerable interest due to the possible non-Fermi liquid behavior, a spin (or cluster) glass state, itinerant ferromagnetic states, its proximity to a magnetic quantum critical point, etc. Herein, the density functional theory is used to study the magnetic structure of CaRuO₃ as a function of hydrostatic pressure.

Sodium-bismuth titanate (NBT) and potassium-bismuth titanate (KBT) are lead-free materials, but their functional properties are weaker than observed in lead titanate (PT). Materials with low Pb content may replace the currently used lead materials. The calculations of some of their solid solutions show an increasing value of the bulk modulus when the PT content in KBT and NBT increases.

Element substitution mechanisms and the relations between element substitution sites and thermoelectric performances of Pb/Ge/Sn-doped Cu₁₂Sb₄S₁₃ are investigated. It is found that the most energetically favorable sites and the sites corresponding to preferable optimizing thermoelectric performance are different. A 15-time improvement on ZT of the host by doping is obtained.

The effect of poling method (alternating or direct current poling, ACP or DCP) and thickness is studied for Pb(In_0.5Nb_0.5)O₃–PbTiO₃ (PIN–PT) crystals. The 2 mm ACP 0.655PIN–0.345PT crystals exhibit high piezoelectric coefficient and free permittivity, enhanced by 24% compared to DCP samples, which is attributed to the regular periodic domain structure and a smaller domain width. Decrease in coercive field is also beneficial for the improvement of piezoelectric performance.

Structural and vibrational properties of van der Waals heterobilayers (HBLs) WSe₂/MoSe₂ are studied using density-functional theory. The first-principles results reveal the existence of interlayer rigid-layer shear and breathing phonon modes in the HBLs. These special low-frequency optical modes exist only in bilayers and are paramount to understanding the different scattering mechanisms in layered 2D materials.

The shear modulus and Young's modulus of the P4/mbm BN, proposed herein, are larger than those of P-4m2 B₇N₇, B₁₁N₁₁, and B₁₅N₁₅. Compared with SiC and GaN, P4/mbm BN has a wider bandgap of 4.8 eV, it might be more suitable for making high temperature, high frequency, radiation resistance, and high-power devices.

Corundum energy gap narrowing by cation d (Zr, Nb, Mo)- and s (Mg)-impurities multidoping due to the formation of new partially filled 4d bands inside the undoped α-Al₂O₃ energy gap is calculated within the coherent potential approximation. New insulator and semiconductor corundum-based compounds with strictly defined mutual concentrations of disordered impurities are proposed for novel optoelectronic devices creation.

Chemically clean gold nanoclusters are fabricated on GaAs(001) surface covered by a monolayer of chemisorbed nitrogen atoms. The on-surface Au clusters possess a pronounced anisotropy of both shape and orientation in crystallographic [$1\overline{1}0$] direction on GaAs surface. Localized plasmons of the clusters also reveal rather strong in-surface anisotropy detected by polarized reflection spectroscopy.

Herein, the effects of Se vacancies on the electronic thermal conductance, electrical conductance, Seebeck coefficient, figure of merit and electronic fitness function of TlGaSe₂ layered semiconductor are theoretically studied. The findings indicate that Se-vacancies can improve the thermoelectric performance of TlGaSe₂. This work provides concrete ways to enhance the thermoelectric performance of TlGaSe₂ by defect engineering and modeling.

The luminescence characteristics of the hexagonal GaN and cubic GaN on micropatterned Si(100) substrates are explored. Photoluminescence and cathodoluminescence measurements reveal that a cubic InGaN/GaN quantum well has produced longer wavelengths. The cubic multiple quantum wells could incorporate higher indium content and realize longer wavelength emissions, which has great potential to realize red light emitting diode.

The authors show that reflection electron energy loss spectroscopy (REELS) can be used to measure the bandgaps of organic semiconductors. By combining REELS and ultra-violet photoemission spectroscopy (UPS), it is further shown that all key energy structures such as bandgap, ionization energy, Fermi energy level, work function, electron affinity, HOMO and LUMO can be concurrently measured from the same sample.

Optical bandgap is determined from Kubelka–Munk function fit to the UV–vis spectra. A frequency-dependent cusp at 3.3 K in the ac susceptibility appears due to short-range correlations among Dy³⁺-moments in Ba₂DySbO₆.

The authors calculate microscopically the band alignment at different GaInP/AlInP (001) interfaces between CuPt-type ordered crystals. The values support previous natural band offset data, indicating a type-I alignment and demonstrate a minor influence of strain and local bonding scenarios.

The dielectric constants and polarization responses of ferroelectric KSr₂Nb₅O₁₅ are different when vacancy is formed at the two types of Nb sites (Nb1 or Nb2), respectively. Furthermore, the experimental results support the effects of different Nb⁵⁺ vacancies on the polarization behavior of the material. This study provides a theoretical foundation for improving the polarization behavior of tungsten bronze structure ferroelectrics.

2D metals are emerging materials in the field of materials science. Herein, attention is paid to investigate the energetic stability and electronic properties of coinage-metal-patched graphene to probe its applications. All the systems are metallic except eight-Au-patched graphene. Cu-patched graphene is more selective for CO adsorption compared to Ag- and Au-patched graphene surfaces.