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The aim is to examine the spin‐polarized electronic band structures, the density of states (DOS) as well as magnetism of CoxZn1−xSe and NixZn1−xSe diluted magnetic semiconductors (DMSs) in the ferromagnetic (FM) phase, and with 12.5% and 6.25% concentrations of impurity. The calculations are implemented by the recent ab initio norm‐conserving FHI pseudopotential method within the local spin density approximation and Hubbard U (LSDA + U) method. The analysis of the total DOS (TDOS) curves shows the half‐metallic FM character for Ni‐doped and (Co, Ni)‐co‐doped ZnSe with a half‐metallic bandgap of 1 ÷ 1.6 eV. The exchange splittings produced by dopant d states are determined: for the CoxZn1−xSe, it is obtained that the effective potential for the majority spin is more attractive than for the minority spin. The total magnetic moments of Co‐doped, Ni‐doped, and co‐doped ZnSe DMSs are found to be equal to 3, 4, and 5.0 μB, respectively. The Curie temperature of NixZn1−xSe is higher than room temperature and this is half‐metallic ferromagnetic (HMFM) material for spintronics application. Co‐doped ZnSe is an excellent choice for electronic devices owing to its below Curie temperature. [ABSTRACT FROM AUTHOR]

Distinguishing between different handedness of circularly polarized light can be a useful additional property in photodetector technology. The integration of this functionality can be obtained either using optical media with chiro‐optical response, or by the employment of chiral metamaterials. In this work, 3D chiral metasurfaces composed by a 3D helix array, are integrated onto a micrometer‐scale silicon‐based transistor and act as optical filter for circularly polarized light. The technological process involving focused electron beam induced deposition for helix manufacturing is carefully studied with respect to its effect on the phototransistor response. The integrated system exhibits a photoresponse which is dependent on the circular polarization, with a promising asymmetry factor in the visible spectral range. The proposed technology can pave the way for novel potential applications in diverse areas such as materials science, bioimaging, and quantum computing. [ABSTRACT FROM AUTHOR]

MoS2 is a two-dimensional layered transition metal dichalcogenide with unique electronic and optical properties. The fabrication of ultrathin MoS2 is vitally important, since interlayer interactions in its ultrathin varieties will become thickness-dependent, providing thickness-governed tunability and diverse applications of those properties. Unlike with a number of studies that have reported detailed information on direct bandgap emission from MoS2 monolayers, reliable experimental evidence for thickness-induced evolution or transformation of the indirect bandgap remains scarce. Here, the sulfurization of MoO3 thin films with nominal thicknesses of 30 nm, 5 nm and 3 nm was performed. All sulfurized samples were examined at room temperature with spectroscopic ellipsometry and photoluminescence spectroscopy to obtain information about their dielectric function and edge emission spectra. This investigation unveiled an indirect-to-indirect crossover between the transitions, associated with two different Λ and K valleys of the MoS2 conduction band, by thinning its thickness down to a few layers. [ABSTRACT FROM AUTHOR]

It is shown that MnTe-Bi 2 Te 3 system is quasi-binary and in fact hosts three intermediate phases. Along with already known MnBi 2 Te 4 phase, another two, MnBi 4 Te 7 and MnBi 6 Te 10 have been found to exist. All the phases melt incongruently in a very narrow temperature range of 577–590 °C via peritectic reactions. Directional crystal growth results in hetero-phase ingots due to the narrow compositional range and narrow primary crystallization fields. The crystal structure of each phase is a derivation of the prototype tetradymit-type layered structure and the phases constitute a new homologous series with the chemical formula (MnTe)· n (Bi 2 Te 3). X-ray diffraction patterns and Raman spectroscopy of the sorted-out single phase samples show that different phases have different number of the seven (7)- and five (5)-layer blocks and their different stacking manner in the unit cell. In particular, MnBi 2 Te 4 exhibits the -7-7-7-, MnBi 4 Te 7 -5-7-5-7-, and MnBi 6 Te 10 -5-5-7-5-5-7- sequence of the blocks. Thus, these structures are the first derivatives of Bi 2 Te 3 structure to contain a transition metal cation Mn2+. • Phase diagram of the MnTe-Bi 2 Te 3 quasi-binary system was plotted. • Novel ternary compounds, MnBi 4 Te 7 and MnBi 6 Te 10 were found in the system along the known MnBi 2 Te 4. • Single crystals of all the three compounds were grown by the Bridgman-Stockbarger method. • Crystal structure of the sorted-out compounds were elucidated from powder data. • All the three ternary compounds were characterized by Raman spectroscopy. [ABSTRACT FROM AUTHOR]

The phase equilibria of the Sb 2 Te 3 +2BiI 3 ↔Bi 2 Te 3 +2SbI 3 reciprocal system have been investigated over the entire concentration range using differential thermal analysis (DTA), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM) techniques. Liquidus surface projection, solid-phase equilibrium diagram at 300 K and a number of isopleths sections of phase diagram were constructed based on experimental results and literature data. The primary crystallization areas of all the existing phases, their homogeneity ranges, as well as, types and coordinates of non- and monovariant equilibria were revealed. It is determined that the BiTeI−SbTeI section of this reciprocal system is non-quasi-binary due to the incongruent melting of one of the initial ternary compound. However, it is stable at subsolidus and forms wide areas of solid solutions based on the initial compounds. Additionally, dielectric functions and Raman spectra of Bi 1−x Sb x TeI (x=0; 0.05 and 0.1) phases were studied. The nature of the dependence of the dielectric function on the photon energy was identified based on the obtained ellipsometric data, while Raman spectra show that no structural changes were observed with an increasing concentration of antimony in the solid solution. • The phase equilibria of the Sb 2 Te 3 + 2BiI 3 ↔Bi 2 Te 3 + 2SbI 3 reciprocal system were investigated and new cation-substituted solid solutions were prepared. • The crystal lattice parameters, dielectric function, and Raman characteristics of Bi 1- x Sb x TeI solid solutions were determined in the compositional range of 0–0.1. • The obtained Bi 1- x Sb x TeI solid solution phases were found to be Rashba-type degenerate semiconductors with well -defined free carrier plasma edge and band gap energy less than 0.45 eV. [ABSTRACT FROM AUTHOR]

Submicron thin films of Bi2Te2,7Se0,3 solid solution is synthesized by thermal vacuum evaporation. The films are then subjected to after-growth vacuum annealing and characterized using X-ray diffraction and confocal laser microscopy techniques. Electron transport in the synthesized films is studied over the temperature range of 1.4-300 K at magnetic fields up to 8 T. Electron localization due to electron-electron interaction, along with weak anti-localization effect at weak magnetic fields and temperatures below 8 K is observed. The latter effect is commonly encountered in thin films of topological insulators grown by molecular beam epitaxy and has therefore been ascribed to the manifestation of the topological surface states. Finally, phase coherence length is estimated. [ABSTRACT FROM AUTHOR]

Highlights from the article: Synthesis, Powder X-Ray Diffraction, and Ab Initio Study of TlInSe2: Analysis of Its Thermoelectric Properties Seyidov, and co-workers report first-principles calculations of the Seebeck coefficient in TlInSe SB 2 sb . The hybridization of Se and Tl orbitals near the top of valence band as well as Se, Tl, and In orbitals in conduction band may lead to giant values of the Seebeck coefficient as it is reported in literature.

In this paper, the authors report first‐principles calculations of the Seebeck coefficient in TlInSe2. Experimental measurements demonstrate that TlInSe2 is characterized by giant values of the Seebeck coefficient at the temperature region of 320–430 K. To get insight on significant enhancement of Seebeck coefficient under temperature changing the density functional theory (DFT) and the Boltzmann transport equation are applied to calculate the semiclassical transport coefficients for TlInSe2 and its constructed models. The molecular dynamic simulations of 2 × 2 × 2 and 1 × 1 × 8 superlattices of TlInSe2, the TlInSe2_118a, TlInSe2_118b, TlInSe2_222a, TlInSe2_222b structures are performed to study their behavior in both "bulk" and "chain – like" modes. It is found that the distortions of InSe4 tetrahedra and displacements of Tl atom lead to formation of Tl–Se covalent bonds. The "bulk" TlInSe2_222b compound possesses the maximum value of Seebeck coefficient and (ZT)max in comparison with another studied compounds. The hybridization of Se and Tl orbitals near the top of valence band and hybridization of the Se, Tl, and In orbitals in conduction band may lead to increasing of Seebeck coefficient in TlInSe2 at 425 K. [ABSTRACT FROM AUTHOR]