Sb Atoms Research Articles

Effects of GaSb surface preparation on the characteristics of HfO2/Al2O3/GaSb metal-oxide-semiconductor capacitors prepared by atomic layer deposition

The electrical, structural, and chemical properties of HfO2/Al2O3/GaSb metal-oxide-semiconductor capacitors (MOSCAPs) fabricated on Sb-rich (2 × 5) and Sb-stabilized (1 × 3) surfaces by atomic layer deposition are characterized. A combination of the transmission electron microscopic, x-ray photoelectron spectroscopic, and atomic force microscopic observations shows that the Sb-rich surface, with its excessive Sb atoms and clusters, leads to island deposition of the dielectric materials and results in the high leakage current of the MOSCAPs. For the MOSCAPs fabricated on the Sb-stabilized (1 × 3) surface, a density of interface traps as low as 8.03 × 1011 cm−2 eV−1 near the valence band and 1.86 × 1012 cm−2 eV−1 at the midgap is obtained as estimated by the conductance method.

High-Surface-Area Antimony Sulfide Chalcogels

Chalcogels are a new class of aerogel materials with diverse properties relevant to catalysis, ion-exchange, and gas adsorption. We report the synthesis of high-surface-area antimony sulfide chalcogels through the sol–gel process followed by supercritical drying. Four different synthetic routes were employed: (1) hydrolysis of sodium thioantimonite (Na3SbS3); (2) ligand metathesis between Sb3+ metal linker and SbS33– anion; (3) reaction of Sb2S3 with Na2S·9H2O; and (4) reaction of Sb2S3 with KOH. All these reactions enable the formation of antimony sulfide gels. The aerogels derived after supercritical drying exhibit high porosity with Brunauer−Emmett−Teller (BET) surface areas up to 300 m2 g–1. The oxidation state of antimony in these chalcogels has been assigned by X-ray photoelectron spectroscopy (XPS) to be +3. Pair distribution function analysis suggests that the local environment around the Sb atoms is very similar to that of crystalline Sb2S3. All the antimony sulfide chalcogels possess the band gap of ∼1.75 eV, and they are thermally stable even up to 600 °C.

X-dependence of energy band structures and thermoelectricity of CeRu4X12 (X = P, As, Sb)

The electronic structures of the filled skutterudites CeRu4X12 (X = P, As, Sb) are calculated using the first-principles density functional theory to understand the region close to Fermi energy level (EF). The effects of the localized electrons present in the sample materials are treated by including the Hubbard’s ‘U’ term in the calculation. The study of the energy band structures suggests the semiconducting nature of CeRu4P12 and CeRu4As12 with the presence of an indirect energy of 0.227 and 0.146 eV, respectively. The addition of Sb atom diminishes the opening of the hybridized energy band-gap above the EF, giving the metallic nature for CeRu4Sb12. The analysis of the thermal transport properties suggests the high value of Seebeck coefficient with large thermopower at room temperature.

Theoretical investigations of half-metallic ferromagnetism in new Half–Heusler YCrSb and YMnSb alloys using first-principle calculations

Structural, electronic, and magnetic properties of new predicted half-Heusler YCrSb and YMnSb compounds within the ordered MgAgAs C1b-type structure are investigated by employing first-principal calculations based on density functional theory. Through the calculated total energies of three possible atomic placements, we find the most stable structures regarding YCrSb and YMnSb materials, where Y, Cr(Mn), and Sb atoms occupy the (0.5, 0.5, 0.5), (0.25, 0.25, 0.25), and (0, 0, 0) positions, respectively. Furthermore, structural properties are explored for the non-magnetic and ferromagnetic and anti-ferromagnetic states and it is found that both materials prefer ferromagnetic states. The electronic band structure shows that YCrSb has a direct band gap of 0.78 eV while YMnSb has an indirect band gap of 0.40 eV in the majority spin channel. Our findings show that YCrSb and YMnSb materials exhibit half-metallic characteristics at their optimized lattice constants of 6.67 Å and 6.56 Å, respectively. The half-metallicities associated with YCrSb and YMnSb are found to be robust under large in-plane strains which make them potential contenders for spintronic applications.

Effects of a magnetic Fe monolayer on the structural and surface electronic properties ofSb2Te3

In this paper, we investigate the properties of Fe monolayers deposited on the (111) surface of the topological insulator $\mathrm{S}{\mathrm{b}}_{2}\mathrm{T}{\mathrm{e}}_{3}$ by density functional theory simulations. We consider high-coverage monolayers and assume ferromagnetic configurations. We show that upon relaxation, the Fe atoms partly penetrate into the surface and that their magnetic moments are reduced due to the chemical interaction with the Te and Sb atoms of the two topmost layers. We compute the magnetic anisotropy energies and show that the easy axis is in-plane. We investigate hexagonal warping effects and find that the clean $\mathrm{S}{\mathrm{b}}_{2}\mathrm{T}{\mathrm{e}}_{3}$(111) displays a large warping term. In spite of this, the surface-state gap for in-plane magnetization is below 1 meV. For very high coverages corresponding to three Fe atoms in the unit cell of $\mathrm{S}{\mathrm{b}}_{2}\mathrm{T}{\mathrm{e}}_{3}$(111), no surface Dirac cones are observed except in the case of a metastable model consisting of a hexagonal Fe monolayer lying on top of the substrate, which also exhibits an out-of-plane easy axis. Finally, we discuss the relevance of our paper to recent experiments about magnetic impurities deposited on topological insulators.

{[CuSn5 Sb3 ](2-) }2 : A Dimer of Inhomogeneous Superatoms.

Reaction of the binary Zintl anion (Sn2 Sb2 )(2-) with the β-diketiminato complex [LCu(NCMe)] (L=nacnac=[(N(C6 H3 (i) Pr2 -2,6)C(Me))2 CH](-) ) in ethylenediamine or DMF affords the ternary cluster dimer {[CuSn5 Sb3 ](2-) }2 (1) as its [K(crypt-222)](+) salt. The chemical formulation of 1 is supported by energy-dispersive X-ray spectroscopy (EDX) and quantum chemical calculations. Each monomeric part of the dimer represents a trimetallic "[CuSn5 Sb3 ](2-) " cluster, with an architecture in between a tricapped trigonal prism and a capped square antiprism. As shown by quantum chemical investigations, the presence of Sb atoms and, in particular, of Cu atoms in the cluster skeleton makes the monomeric unit behave like an inhomogeneous superatom, which clearly prefers to dimerize, thereby producing a relatively short, yet virtually non-bonding Cu⋅⋅⋅Cu distance.

Towards band gap engineering in skutterudites: The role of X4 rings geometry in CoSb3-RhSb3 system

Strong relationship between direct X-X bonds and electronic properties in many thermoelectric materials is observed. In present work investigation on the relation between properties of such bonds in skutterudite-structured compounds and band gap size was performed. Various compositions of Co1-xRhxSb3 (x = 0 to 1) solid solutions were studied theoretically, using experimental structure data found in a literature as well as structures optimized through ab initio methods. Electronic structure of a set of pure CoSb3/RhSb3 structures subjected to various external pressure conditions as well as solid solutions was obtained within DFT calculations using WIEN2k package. Topological properties of total electron density were determined under Bader's QTAiM formalism. Importance of charge transfer changes between Co/Rh and Sb atoms and their relation to the band structure were highlighted. According to presented results, strong influence of longer Sb-Sb bonds of Sb4 ring on the band structure was explained, suggesting possible ways of CoSb3-RhSb3 band gap engineering.

Crystallization properties of Sb-rich GeSbTe alloys by in-situ morphological and electrical analysis

Phase Change Memory (PCM) operation relies on the reversible transition between two stable states (amorphous and crystalline) of a chalcogenide material, mainly of composition Ge2Sb2Te5 (GST). In Wall type PCM cells, cycling endurance induces a gradual change of the cell electrical parameters caused by variations in the chemical composition of the active volume. The region closer to the GST-heater contact area, becomes more Sb rich and Ge depleted. The new alloy has usually different thermal characteristics for the phase transitions that influence the electrical behavior of the cell. In this study we analyze the morphological, structural and electrical properties of two Sb-rich non-stoichiometric alloys: Ge14Sb35Te51 and Ge14Sb49Te37, at their amorphous and crystalline phase. Experiments have been performed in non-patterned blanket films and, to simulate the device size, in amorphous regions of 20nm, 50nm and 100nm diameter respectively. The amorphous Ge14Sb35Te51 film crystallizes in the meta-stable face centered cubic structure at 150°C and in the rhombohedral phase at 175°C, behavior characteristic of the Ge1Sb2Te4 composition. The average grain size is of about 100nm after an annealing at 400°C. The Ge14Sb49Te37 film crystallizes only in the hexagonal phase, with an average grain size of about 60nm after annealing at 400°C. The X-ray fluorescence analysis shows a non uniform distribution of the constituent atoms and in particular a Ge signal decrement and a Sb enrichment at grain boundaries. The in situ annealing of amorphous nano-areas (RESET state under a thermal stress) indicates a fast re-crystallization speed for Ge14Sb35Te51, 80pm/s at 90°C, and a lower speed for Ge14Sb49Te37, at 130°C a grain growth velocity of 50pm/s has been measured. The different behavior of the two alloys is discussed in terms of structural vacancies filling by the Sb atoms in excess and by their segregation at grain boundaries. The influence of the obtained results on the device characteristics is discussed.

Synthesis and structure of tris(4-fluorophenyl)antimony dicarboxylates

The interaction of tris(4-fluorophenyl)antimony with chloroacetic, 4-nitrophenylacetic, and benzoic acids in diethyl ether in the presence of tert-butyl hydroperoxide has yielded tris(4-fluorophenyl)antimony dicarboxylates, their Sb atoms bearing distorted trigonal bipyramid coordination with the carboxylate ligands in the axial positions. The intramolecular contacts between Sb atom and carbonyl O atom are formed in the molecules of the products. Their crystal packing is determined by weak intermolecular hydrogen bonds of the H···F and H···O=C types.

Improved thermal stability of C-doped Sb2Te films by increasing degree of disorder for memory application

The structural stability of carbon (C) incorporated Sb2Te films was investigated during crystallization process. Variations in the transition temperature for the as-deposited films during crystallization show that these films exhibit their enhanced amorphous stability due to C incorporation, while more C content will lead to a difference in the degree of disorder in the crystalline state. XPS data reveals that C atoms do not bond with Sb and Te atoms and only present in the form of CC bonds. According to XRD and TEM results, C atoms presents amorphous and this can increase the degree of disorder in the crystalline films. The Sb2Te nanocrystals were surrounded by an amorphous C phase. A subsequent Raman analysis further provides the direct evidence of improvement in the degree of disorder in the crystalline state. The laser-induced crystallization process of C37.4(Sb2Te)62.6 reveals that the degree of disorder in the crystalline state is relatively high and the reliability during the repetitive laser melt-quenching cycles is confirmed with fast crystallization as well as a low melting point of only 353°C. Increasing degree of disorder in the Sb2Te films by C addition can improve the phase-change behavior and make this film suitable for data storage applications.

Optimizing the Dopant and Carrier Concentration of Ca5Al2Sb6 for High Thermoelectric Efficiency.

The effects of doping on the transport properties of Ca5Al2Sb6 are investigated using first-principles electronic structure methods and Boltzmann transport theory. The calculated results show that a maximum ZT value of 1.45 is achieved with an optimum carrier concentration at 1000 K. However, experimental studies have shown that the maximum ZT value is no more than 1 at 1000 K. By comparing the calculated Seebeck coefficient with experimental values, we find that the low dopant solubility in this material is not conductive to achieve the optimum carrier concentration, leading a smaller experimental value of the maximum ZT. Interestingly, the calculated dopant formation energies suggest that optimum carrier concentrations can be achieved when the dopants and Sb atoms have similar electronic configurations. Therefore, it might be possible to achieve a maximum ZT value of 1.45 at 1000 K with suitable dopants. These results provide a valuable theoretical guidance for the synthesis of high-performance bulk thermoelectric materials through dopants optimization.

Prediction of spin-dependent electronic structure in 3d-transition-metal doped antimonene

We investigate the geometric structure and electronic and magnetic properties of 3d-transition-metal atom doped antimonene using spin-polarized first-principles calculations. Strong orbital hybridization exhibits between 3d-transition-metal and Sb atoms, where covalent bonds form in antimonene. A spin-polarized semiconducting state appears in Cr-doped antimonene, while half-metallic states appear by doping Ti, V, and Mn. These findings indicate that once combined with doping states, the bands of antimonene systems offer a variety of features. Specific dopants lead to half-metallic characters with high spin polarization that has potential application in spintronics.

Tetra(para-Tolyl)antimony aroxides (4-MeC6H4)4SbOAr (Ar = C6H3Cl2-2,6, C6H3(NO2)2-2,4, and C6H2(NO2)3-2,4,6): Syntheses and structures

Tetra(para-tolyl)antimony aroxides, [(4-MeC6H4)4SbOC6H3Cl2-2,6] • 1/2TolH (IА, IВ), (4-MeC6H4)4SbOC6H3(NO2)2-2,4 (II), and (4-MeC6H4)4SbOC6H2(NO2)3-2,4,6 (III), are synthesized by the reactions of penta-para-tolylantimony with 2,6-dichlorophenol, 2,4-dinitrophenol, and 2,4,6-trinitrophenol, respectively, in toluene. The structures of the synthesized compounds are determined by X-ray diffraction analysis (CIF files CCDC 1050584 (I), 1433797 (II), and 999305 (III)). The Sb atoms in compounds IА, IВ, and II have a distorted trigonal bipyramidal coordination with the aroxy groups in the axial positions (axial angles CSbO are 178.01(6)°, 177.74(7)°, and 174.42(11)° and Sb–O angles are 2.244(1), 2.230(2), and 2.507(3) A). In crystal III, the CSbC angles in the tetrahedral cation [(4-MeC6H4)4Sb]+ are 103.6(2)°–116.22(2)°. A weak interaction is observed between the cation and picrate anion [OC6H2(NO2)3-2,4,6]–(Sb···O distance is 3.472(3) A).

Features of conductivity mechanisms in heavily doped compensated V1–x Ti x FeSb Semiconductor

The crystal and electronic structure and also the energy and kinetic properties of n-VFeSb semiconductor heavily doped with the Ti acceptor impurity are investigated in the temperature and Ti concentration ranges of T = 4.2–400 K and NATi ≈ 9.5 × 1019–3.6 × 1021 cm–3 (x = 0.005–0.20), respectively. The complex mechanism of the generation of acceptor and donor structural defects is established. It is demonstrated that the presence of vacancies at Sb atomic sites in n-VFeSb gives rise to donor structural defects (“a priori doping”). Substitution of the Ti dopant for V in VFeSb leads simultaneously to the generation of acceptortype structural defects, a decrease in the number of donor defects, and their removal in the concentration range of 0 ≤ x ≤ 0.03 via the occupation of vacancies by Sb atoms, and the generation of donor defects due to the occurrence of vacancies and an increase in their number. The result obtained underlies the technique for fabricating new n-VFeSb-based thermoelectric materials. The results are discussed in the context of the Shklovsky–Efros model for a heavily doped compensated semiconductor.

Exponential improving in the activity of Pt/C nanoparticles towards glycerol electrooxidation by Sb ad-atoms deposition

Tuning the chemical composition of heterogeneous nanocatalysts has emerged as an efficient strategy to improve their electroactivity and selectivity for electrolizers and fuel cells application. The stability of a catalyst is ascribed as the ability of the nanoparticles (NPs) in maintaining their chemical composition and physical structure during recycles of use. By an electrochemical procedure, here we decorated platinum nanoparticles supported on carbon with different coverage degrees of antimony ad-atom (θSb) to investigate glycerol electrooxidation reaction (GEOR). The successful decoration of Pt/C with Sb was monitored by electrochemical and physicochemical characterizations. θSb is highly dependent on the upper potential applied. Sb atoms are rapidly leached from Pt surface in potentials greater than 0.7V in acid solution while they remain stable during several cycles in potentials lower than that. We showed that the current density of GEOR exponentially increases with the increase of Sb coverage, reaching 109 times the pseudo stationary current density of Pt/C for high θSb. Furthermore, the ad-atom facilitates the reaction by shifting the onset potential towards lower potentials. We found an improvement of −320mV in the onset for θSb=0.81.

Analysis of the Structures and Properties of (GaSb)n (n = 4-9) Clusters through Density Functional Theory.

An optimization strategy combining global semiempirical quantum mechanical search with all-electron density functional theory was adopted to determine the lowest energy structure of (GaSb)n clusters up to n = 9. The growth pattern of the clusters differed from those of previously reported group III-V binary clusters. A cagelike configuration was found for cluster sizes n ≤ 7. The structure of (GaSb)6 deviated from that of other III-V clusters. Competition existed between core-shell and hollow cage structures of (GaSb)7. Novel noncagelike structures were energetically preferred over the cages for the (GaSb)8 and (GaSb)9 clusters. Electronic properties, such as vertical ionization potential, adiabatic electron affinities, HOMO-LUMO gaps, and average on-site charges on Ga or Sb atoms, as well as binding energies, were computed.

AgPbmSbTem+2 microspheres comprised of self-assembled nanoparticles driven by inhomogenous co-doping synergetic induced dipoles and their thermoelectric and electrochemical Li-storage properties

Design and fabrication of low-cost, high efficient and robust three-dimensional (3D) microspherical materials for energy conversion and storage is of paramount importance. Here, we first reported a template-free and efficient hydrothermal method to synthesize quaternary AgPb10SbTe12 (AgPbmSbTem+2, m=10) microspheres comprised of tiny nanoparticles driven by co-doping synergetic dipole-driven aggregation. Due to the effect of site blocking, Ag and Sb atoms tend to segregate into Ag-rich and Sb-rich regions, creating substantial inhomogeneity on the nanoscale. Theoretical calculations confirm the dipole-field-driven mechanism forming the microsphere structure. The inhomogeneous local structure has a high impact on the physical properties of the synthesized compounds: the local Ag/Sb ordering and multiple nanoscale interfaces result in the improved thermoelectric performance and cycling stability during the lithiation/delithiation process in Li ion battery compared to their binary or ternary compounds.

First-principles study of new series of quaternary Heusler alloys CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb)

The structural, electronic, magnetic, and thermal properties of new quaternary Heusler alloys CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb) were investigated using the full-potential linearized augmented plane wave (FPLAPW) within the generalized gradient approximation (GGA) and GGA plus modified Becke and Johnson as the exchange correlation. The results showed that all Heusler compounds were stable in Type (I) structure. The CsSrCZ (Z=Si, Ge, Sn) compounds had a nearly HM characteristic, and CsSrCZ (Z=P, As, Sb) compounds were true half-metallic (HM) ferromagnets. The strong spin polarization of p orbital for C, Si, Ge, Sn, P, As, and Sb atoms is found to be the origin of ferromagnetic. The half-metallicity is preserved up to a lattice contraction of 3.45%, 1.69%, 1.69%, 7.16%, 7.16%, and 11.2% for all six quaternary Heusler compounds. We also investigated the thermal effects using the quasi-harmonic Debye model.

On the tin impurity in the thermoelectric compound ZnSb: Charge-carrier generation and compensation

The technique for measuring the Hall coefficient and electrical conductivity in the thermal cycling mode is used to study the effect of the Sn impurity on the microstructure and properties of pressed ZnSb samples. Tin was introduced as an excess component (0.1 and 0.2 at %) and as a substitutional impurity for Zn and Sb atoms in a concentration of (2–2.5) at % The temperature dependences of the parameters of lightly doped samples are fundamentally like similar curves for ZnSb with 0.1 at % of Cu. The highest Hall concentration, 1.4 × 1019 cm–3 at 300 K, is obtained upon the introduction of 0.1 at % of Sn; the dimensionless thermoelectric figure of merit attains its maximum value of 0.85 at 660 K. The experimental data are discussed under the assumption of two doping mechanisms, which are effective in different temperature ranges, with zinc vacancies playing the decisive role of acceptor centers. In two ZnSb samples with SnSb and ZnSn additives, the charge-carrier compensation effect is observed; this effect depends on temperature and markedly changes with doping type. As in p-type AIV–BVI materials with a low Sn content, hole compensation can be attributed to atomic recharging Sn2+ → Sn4+. Types of compensating complexes are considered.

Tuning electronic and magnetic properties of blue phosphorene by doping Al, Si, As and Sb atom: A DFT calculation

Abstract Using density functional theory computations, we systematically investigated the structural, electronic and magnetic properties of Al, Si, As and Sb doped blue phosphorene. The electronic properties of blue phosphorene can be effectively turned by substitutional doping. Especially, Al and Sb lead to an indirect-to-direct-gap transition. The interaction between the impurity and P atoms should be responsible for the transition. In addition, blue phosphorene can exhibit dilute magnetic semiconductor property with doping of Si impurity. The magnetic moment in Si-substituted blue phosphorene predominantly originates from the hybridization of Si-s p z and P-p z orbitals. These results provide many useful applications of blue phosphorene in electronics, optoelectronics and spintronics.