Sb Composition Research Articles

Exploring the impact of variation of Cu and Sb composition on thermoelectric performance and photosensing abilities in Bridgman grown CuxSb1-xS2 (x = 0.2, 0.4, 0.6, 0.8) crystals

In this study, we have grown CuxSb1-xS2 (x = 0.2, 0.4, 0.6, 0.8) crystals using Bridgman technique by varying compositions of Cu and Sb and explored the impact on its structural, optical, thermal and electrical properties compared to pure CuSbS2. X-ray diffraction analysis confirmed the orthorhombic CuSbS2 phase and secondary phases due to different compositions of Cu and Sb. Stoichiometry of each crystal was verified through Energy dispersive X-ray analysis and uniform distribution was observed in elemental mapping. Field emission microscopy in scanning mode validated the flat surface and layer growth mechanism of all crystals. Raman spectroscopic measurements indicated the presence of Ag vibration modes with red shift in all crystals. The direct bandgap of CuxSb1-xS2 (x = 0.2, 0.4, 0.6, 0.8) crystals reduces from 1.65 eV to 1.61 eV with increasing Cu content which is determined using Kubelka-Munk function. These suitable bandgaps positioned them as promising candidates for optoelectronic applications. All four crystals were identified as p-type semiconductors based on variations in Seebeck coefficient (S), dc electrical conductivity (σ), and thermal conductivity (κ) within the temperature range of 313 K–573 K. Analysis of temperature-dependent variations in the power factor (S2σ) and figure of merit (ZT) highlighted the superior performance of Cu0.4Sb0.6S2 crystal compared to other grown crystals, reaching a maximum ZT value of 0.038 at 573 K. Thermogravimetric profiles conducted under nitrogen (N2) atmosphere revealed two-step decomposition for all crystals, with Cu0.4Sb0.6S2 experiencing the highest weight loss of 9.55 % and Cu0.8Sb0.2S2 displaying the lowest weight loss of 2.46%. Room temperature I–V characteristics and pulse photoresponse of prepared CuxSb1-xS2 (x = 0.2, 0.4, 0.6, 0.8) crystals photodetectors were measured for parallel to plane configuration, revealing that Cu0.6Sb0.4S2 exhibited the highest responsivity and detectivity of 32.718 μ A/W and 15.267 × 106 Jones, respectively.

Fabrication of modified Sb2O3 nanospheres for the removal of hazardous malachite green organic pollutant and selective NO2 gas sensor

Sb2O3 and Ni modified Sb2O3 (Ni–Sb2O3) nanospheres were synthesized using low cost co-precipitation method and characterised using various instrumental methods such as X-ray Powder Diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared (FT-IR) spectroscopy. The XRD pattern reveals cubic crystal lattice. The average size of Sb2O3 and Ni–Sb2O3 nanoparticles was calculated to be around 41 nm and 29 nm, respectively. The HR-TEM investigation of the Sb2O3 nanomaterial reveals homogeneous spherical balls with a fine dispersion. The random-shaped nanoparticles with porous surfaces and voids were revealed by SEM. EDS examination confirms the elemental composition of Sb (41.79 %) and O (58.21 %) in Sb2O3 and Sb (36.80 %), O (58.95 %), and Ni (4.25 %) in Ni–Sb2O3. Sb2O3 and Ni– Sb2O3 exhibit band gaps of 3.67 eV and 3.51 eV, respectively, according to UV–Vis analysis. The IR peaks 445.47, 642.18, and 745.18 in Sb2O3 and 438.72, 645.07, and 756.92 in Ni– Sb2O3 support the Sb–O bonding in the synthesized nanomaterials. The synthesized nanomaterials have been used for photocatalytic degradation of malachite green (MG) dye and sensing NO2, SO2, CO2, petroleum vapour and LPG gases. The MG dye was degraded 97.67 % in 120 min using Ni–Sb2O3 at optimized conditions (catalyst dose: 0.1 g/L to 0.3 g/L, pH: 7 and MG dye: 10 ppm). The gas sensing study showed that Ni–Sb2O3 sensor has greater sensitivity and selectivity for NO2 gas.

Opto‐Electronic Properties of Gap1‐xSbx Alloys for IR Applications

AbstractThe full potential linearized augmented plane wave (FP‐LAPW) method is used to compute structural, electronic, and optical properties of III‐V semiconductor ternary alloys GaP1‐xSbx (0≤x≤1) using first‐principle calculations within density functional theory. To calculate the ground state parameters of the structure, the energy exchange‐correlation Wu‐cohen generalized gradient approximation is employed in the wiek2k program. The Tran–Blaha‐modified Becke–Johnson (TB‐mBJ) pseudopotential is employed in addition to the Wu‐Cohen generalised gradient approximation to achieve a precise bandgap. After this, WC‐mBJ is used to examine optical properties such as real and imaginary parts of the dielectric constant, and energy loss. This study illustrates the nonlinear dependency on the various Sb compositions by examining the composition impacts on the bandgap, bulk modulus, and lattice constant. Using WC‐mBJ, the estimated band structures for alloys GaP0.75Sb0.25, GaP0.50Sb0.50, and GaP0.25Sb0.75 show direct energy bandgaps of 2.008 eV (617 nm), 1.482 eV (836 nm), and 1.055 eV (1174 nm), respectively. As a result, this material system has enormous potential for use in applications spanning the visible to infrared spectrum.

Impact of Modifications from Potassium Hydroxide on Porous Semi-IPN Hydrogel Properties and Its Application in Cultivation.

This study synthesized and modified a semi-interpenetrating polymer network hydrogel from polyacrylamide, N,N'-dimethylacrylamide, and maleic acid in a potassium hydroxide solution. The chemical composition, interior morphology, thermal properties, mechanical characteristics, and swelling behaviors of the initial hydrogel (SH) and modified hydrogel (SB) in water, salt solutions, and buffer solutions were investigated. Hydrogels were used as phosphate fertilizer (PF) carriers and applied in farming techniques by evaluating their impact on soil properties and the growth of mustard greens. Fourier-transform infrared spectra confirmed the chemical composition of SH, SB, and PF-adsorbed hydrogels. Scanning electron microscopy images revealed that modification increased the largest pore size from 817 to 1513 µm for SH and SB hydrogels, respectively. After modification, the hydrogels had positive changes in the swelling ratio, swelling kinetics, thermal properties, mechanical and rheological properties, PF absorption, and PF release. The modification also increased the maximum amount of PF loaded into the hydrogel from 710.8 mg/g to 770.9 mg/g, while the maximum % release of PF slightly increased from 84.42% to 85.80%. In addition, to evaluate the PF release mechanism and the factors that influence this process, four kinetic models were applied to confirm the best-fit model, which included zero-order, first-order, Higuchi, and Korsmeyer-Peppas. In addition, after six cycles of absorption and release in the soil, the hydrogels retained their original shapes, causing no alkalinization or acidification. At the same time, the moisture content was higher as SB was used. Finally, modifying the hydrogel increased the mustard greens' lifespan from 20 to 32 days. These results showed the potential applications of modified semi-IPN hydrogel materials in cultivation.

Tuning the emission wavelength by varying the Sb composition in InGaAs/GaAsSb “W” quantum wells grown on GaAs (001) substrates

Tuning the emission wavelength by varying the Sb composition in InGaAs/GaAsSb “W” quantum wells grown on GaAs (001) substrates

Nitrogen-doped carbon with antimony nanoparticles as a stable anode for potassium-ion batteries

Potassium-ion batteries are considered promising alternatives to lithium-ion batteries (LIBs) because they have a lower redox K+/K potential, a lower Stokes radius, abundant raw materials, and economic benefits. However, K has a larger ionic radius than Li, which may limit the diffusion of K ions into electrodes and cause poor electrode rate capability and cycling stability. In this study, N-doped C and Sb (NC@Sb) composites were synthesised using a facile and cost-effective method of carbonisation and ball milling. The NC@Sb composites had an interconnected and highly porous structure, which was formed by the release of gases such as CO, H2O, CO2, and NH3 during carbonisation. Additionally, NC@Sb is a promising anode owing to the synergistic effects of the high specific capacity of Sb and the good cycling stability of NC. In particular, the NC@Sb composite that contained 10 wt% Sb (NC@Sb10) exhibited a high reversible capacity of 264 mAh g−1 after 100 cycles at a specific current of 200 mA g−1. Furthermore, the NC@Sb10 electrode maintained 85% of its initial capacity at a high specific current of 1 A g−1 even after 500 discharge–charge cycles. The excellent electrochemical performance of the NC@Sb composite is mainly attributed to the stable embedding of the Sb nanoparticles in the porous and electrically conductive NC matrix, which can buffer Sb stress and provide a pathway for the penetration of the electrolyte and K ions.

Effect of SB Addition on Mechanical Electronic and Thermodynamic Properties of Intermetallic B2-NIAL: First Principles Study

Abstract This study investigates the mechanical, electronic, and thermodynamic properties of B2 NiAl alloyed with Sb, ranging from 0% to 100%. The calculations were conducted using the WIEN2k code based on the full potential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) framework. Generalized Gradient Approximation (GGA) was employed to approximate the exchange-correlation energy. Our analysis of formation enthalpy indicates a preference for Sb to substitute Al sites. Furthermore, we have observed that the mechanical properties of NiAl can be enhanced by adjusting the chemical composition of Sb. Specifically, an increase in antimony content from 0% to 75% results in a notable improvement in ductility tensile, elevating it from 1.92 to 10.72. Conversely, this alteration diminishes the material’s strength. Moreover, both the band structures and density of states (DOS) indicate the metallic behavior exhibited by all NiAl1-xSbx compounds. In addition, we employ the Gibbs2 code to calculate thermodynamic properties, shedding light on the influence of temperature and pressure on the volume, heat capacity, Debye temperature and entropy S of NiAl1-xSbx.

Tuning electrical and optical properties of InAs/GaAs1−x Sb x quantum dots

Understanding the electrical and optical properties of InAs/GaAs(Sb) quantum dots (QDs) is essential for designing and improving the performance of related semiconductor QD devices. In this paper, the effects of In segregation, QD size, capping layer thickness and Sb composition on the electrical and optical properties of type I and type II InAs/GaAs1−x Sb x () QDs are systematically investigated and general regularities are summarized. The comparisons of electron distribution probabilities, interband and intraband transition energies and absorption coefficients show that In segregation and QD size have a strong influence on the electron energy level positions of InAs QDs and that the trade-offs between absorption peak energy, absorption intensity and radiative lifetime of InAs/GaAs1−x Sb x QDs can be optimized by adjusting the thickness and Sb composition of the GaAs1−x Sb x capping layer. The results obtained are promising for the applications in the pre-design and performance feedback of the QD devices such as QD lasers, QD infrared detectors and intermediate band solar cells.

Study of CuSb bimetallic flow-through gas diffusion electrodes for efficient electrochemical CO2 reduction to CO

Electrochemical CO2 reduction (eCO2R) to industrially important feedstock has received great attention, but it faces different challenges. Among them, the poor CO2 mass transport due to low intrinsic CO2 solubility significantly limits the rate of reduction reactions, leading to lower catalytic performance; thereby, commercially relevant current densities can’t be achieved. Moreover, the poor activity and selectivity of high-cost monometallic catalysts, including Cu, Zn, Ag, and Au, undermine the efficiency of eCO2R. Flow-through gas diffusion electrodes (FTGDE), a newly developed class of GDEs, can potentially solve the issue of poor CO2 mass transport because they directly feed the CO2 to the catalyst layer. In addition, abundant surface area, porous structure, and improved triple-phase interface make them an excellent candidate for extremely high rate eCO2R. Antimony, a low-cost and abundant metalloid, can be effectively tuned with Cu to produce useful products such as CO, formate, and C2H4 through eCO2R. Herein, a series of porous binary CuSb FTGDEs with different Sb compositions are fabricated for the electrocatalytic reduction of CO2 to CO. The results show that the catalytic performance of CuSb FTGDEs improved with increasing Sb content up to a certain threshold, beyond which it started to decrease. The CuSb FTGDE with 5.4 g of antimony demonstrated higher current density (206.4 mA/cm2) and faradaic efficiency (72.82 %) at relatively lower overpotentials. Compared to gas diffusion configuration, the poor catalytic activity and selectivity achieved by CuSb FTGDE in non-gas diffusion configuration signifies the importance of improved local CO2 concentration and improved triple-phase interface formation in GDE configuration. The several hours stable operation of CuSb FTGDEs during eCO2R demonstrates its potential for efficient electrocatalytic conversion applications.

Enhanced Thermoelectric Performance of p-Type Mg3-xZnxSb2/Sb Composites: The Role of ZnSb/Sb Composites.

Mg3Sb2-based Zintl compounds have garnered recent attention as promising materials for thermoelectric applications due to their low thermal conductivity and high zT values as n-type materials. However, the zT values of p-type materials are lower compared to their n-type counterparts. Through a straightforward process involving cold pressing and evacuating-and-encapsulating sintering, we have successfully synthesized a variety of p-type Mg3-xZnxSb2/Sb composites by adding the ZnSb-4%Sb composite into the Mg3Sb2 host material. Structural analyses have provided insights into the role of the ZnSb-4%Sb composite, demonstrating its significance in Zn doping on the Mg sites and Sb acting as an additive in the composite. The introduction of Zn on the Mg tetrahedral sites enhances the concentration of carriers, while the presence of highly conductive Sb grains facilitates the movement of charge carriers between adjacent Mg3-xZnxSb2 grains, thereby promoting mobility. Consequently, the electrical resistivity of the Mg3-xZnxSb2/Sb composites decreases as the Zn content increases. At 710 K, the Mg1.91Zn1.09Sb2/Sb composite exhibits the lowest resistivity, measuring 5.1 mΩ-cm, which is 46 times lower than that of the Mg3Sb2 host. Furthermore, the zT value of the Mg3-xZnxSb2/Sb composites increases with higher Zn content (x), benefiting from a combination of an improved power factor and reduced thermal conductivity. Significantly, our straightforward fabrication process enables us to achieve a maximum zT value of 0.58 at 710 K for the Mg1.91Zn1.09Sb2/Sb composite. This achievement can primarily be attributed to the 8-fold enhancement in power factor compared to the Mg3Sb2 host.

Improved performance of quantum dot solar cells by type-II InAs/GaAsSb structure with moderate Sb composition

We demonstrate improved performance of quantum dot solar cells (QDSCs) by type-II InAs/GaAsSb structure. With a moderate Sb composition of 18% and high quality QDs, a high efficiency of 17.31% under AM1.5 G illumination is achieved, showing an improvement of 11.25% in efficiency relative to type-I InAs/InGaAs QDSC. This improvement can be attributed to a high fill factor (FF) of 72.37% compared to 63% of the latter because the type-II structure effectively suppresses carrier recombination losses in QDs. As Sb composition increases to 24%, the FF maintains at a high level of 72.67%, but the efficiency drops to 17% because the elevation of valence band (VB) in GaAsSb capping layer further enhances the hole confinement. And the confinement reduces external quantum efficiency (EQE) and short-circuit current density (Jsc). These results prove the potential of improving efficiency of QDSCs by type-II structure.

Structural Transition in (C2H5NH3)3Bi2-xSbxI9:[(Bi/Sb)2I9]3- Dimers to [(Bi/Sb)3I12]3- Trimers to (∞1)[(Bi/Sb)2I93-] 1D Infinite Chains.

Antimony/bismuth-based lead-free hybrid halide defect 2D perovskites have been generating enormous research interest due to their inherent excellent optical properties. Exploration of new phases and understanding of their structural and optoelectronic properties are of paramount importance in the process of developing materials for practical solar cell applications. In this article, we have reported a structural transition from the 0D hexagonal phase containing isolated [M2I9]3- (M = Bi/Sb) units to the 1D orthorhombic phase via a new monoclinic phase with novel isolated trimeric [M3I12]3- units in (C2H5NH3)3Bi2-2xSb2xI9. The hexagonal phase is stable up to 2x = 0.6 in (C2H5NH3)3Bi2-2xSb2xI9. With gradual substitution of Sb, the cation-cation repulsion increases, which destabilizes the [M2I9]3- unit, and hence, the hexagonal phase becomes unstable. At intermediate composition, 2x = 0.8-1.6, a new monoclinic phase (S.G.: C2/m) with the composition (C2H5NH3)2Bi2-2xSb2xI8 is formed, containing isolated [M3I12]3- units. The symmetry reduction resulted in larger distortion, which relaxes the strain and stabilizes the trimeric unit in the intermediate compositions. Finally, at higher Sb compositions (2x = 1.9-2.0), the compounds crystallize in the orthorhombic 1D phase. In all three phases of (C2H5NH3)3Bi2-2xSb2xI9, the cationic ethylammonium units are completely disordered over the whole unit cell. Raman study clearly shows the phase transition in (C2H5NH3)3Bi2-2xSb2xI9 and also the structural distortion in (C2H5NH3)2Bi2-2xSb2xI8. Optical property study shows that all the compounds are of indirect band gap type. Furthermore, PL study shows better emission properties of the 1D orthorhombic Sb compounds as compared to the 0D hexagonal and monoclinic phases.

Compositional dependence of physical parameters of Sb-doped InSe nanochalcogenide alloys

ABSTRACT InSe is a III-VI semiconducting layered compound having potential applications in memories, solar cells, infrared sensors, switching devices and optical fibers. In this article various physical parameters of In0.1Se0.9-x Sb x (x = 0, 0.04, 0.08, 0.12) chalcogenide alloy depending on the varying composition of Se and Sb are discussed. The physical parameters include the theoretical calculations of average coordination number, number of constraints, floppy modes, number of lone pair electrons, deviation of stoichiometry, average heat of atomization, mean bond energy, density, molar volume, compactness, cohesive energy, electronegativity, energy band gap, conduction and valance band energy and glass transition temperature. The number of lone pair electrons and floppy modes is found to decrease, whereas the average coordination number, mean bond energy, average heat of atomization and density are found to increase with increasing Sb content. The theoretical values of glass transition temperature are calculated using the Tichy-Ticha and Lankhorst approach.

Metamorphic growth of 0.1 eV InAsSb on InAs/GaAs virtual substrate for LWIR applications

Epitaxial growth of bulk InAs1-xSbx layer on GaAs substrate could open an opportunity for cost-competitive long-wavelength infrared sensors. Achieving this requires a high-quality metamorphic InAsSb layer with a uniform strain relief buffer design. We report a comprehensive analysis of metamorphic InAsSb layers grown on InAs/GaAs virtual substrate for 0.1 eV low bandgap material with an optimized growth condition and group-V flux control. We find that InAsSb surface roughens significantly with increasing Sb composition up to 58%. Lowering the growth temperature of InAsSb layers from 450 ℃ to 425 ℃ mitigated surface roughening while allowing greater than 90% strain relaxation. Moreover, we also present a dramatically increasing threading dislocation density by more than 200 times as a consequence of high Sb composition. Finally, we demonstrate a narrow energy bandgap of 0.13 eV at 10 K in the InAs0.42Sb0.58 layer, which is close to 0.1 eV at room temperature. This InAsSb film grown on InAs/GaAs template paves the way for long-wavelength infrared optoelectronics applications.

Effect of substrate rotation and rapid thermal annealing on thermoelectric properties of Ag-doped Sb2Te3 thin films

In this work, homogeneous Ag-doped Sb2Te3 (AST) thin films were prepared using the rf magnetron sputtering technique. Thermoelectric properties of AST films have been investigated in terms of various substrate rotation speeds (20, 40, 60, and 80 rpm) and rapid post-thermal treatments at 250 oCin a vacuum. It was found that the thickness of AST films decreases with the increase in substrate rotation speeds. An Ag atomic composition slightly increases and the other Sb and Te atomic compositions slightly decrease with the increase of substrate speed rotations. The post-thermal treatment improved film crystallinity. Carrier scatterings at the grain boundaries tend to increase the resistivity and the Seebeck coefficient. The maximum power factor of 4.60 mW m−1K−2 (ρ = 19 μΩm, S = 298 μVK−1) is obtained in the AST thin films prepared with the substrate rotation speed of 60 rpm. The practical application of AST films was also reported via a thermoelectric module of five p-AST/n-Bi2Te3thin-film pairs with its achieved output power of 1.6 nW at ΔT = 20 K.

High performance InAs0.91Sb0.09 MWIR detectors with an AlAs1-ySby graded barrier

InAs0.91Sb0.09 barrier detectors are an important candidate in realizing high operating temperature middle wavelength infrared (MWIR) photodetectors. Here, an AlAs1-ySby graded barrier layer with linear Sb composition varying from y = 1 to 0.92 is utilized to improve the extraction of photo-generated minority carriers from an InAs0.91Sb0.09 absorber layer. With the modification of valance band misalignment between the absorber and barrier layers, although a hole barrier between AlAs0.08Sb0.92 and InAs0.91Sb0.09 layers exists, the photo-generated holes can be effectively extracted. At 150 K and under zero bias voltage, the maximum quantum efficiency of the devices with a graded barrier reaches ∼56 %, which is much higher than that of the device with a uniform AlAs0.08Sb0.92 barrier. Benefiting from the low dark current density at small reverse bias voltages, a maximum specific detectivity (D*) ∼6.19 × 1011 cm⋅Hz1/2/W is realized at zero bias voltage, which is 50 % higher than the maximum D* ∼4.26 × 1011 cm⋅Hz1/2/W of the uniform barrier device operated at −150 mV bias voltage.

Origin and geochemical significance of antimony in Chinese coal

A total of 159 coal samples from different regions, periods and ranks across China were systematically analyzed for antimony (Sb) isotopic composition (ε123Sb), trace element contents and total sulfur content (TS) in this study. Here, we discuss the origin of Sb in coal from different regions of China. Antimony in coal from SW and NE China is primarily of hydrothermal fluid and leachate origins, respectively. In comparison, Sb in northern Chinese coal mainly comes from terrigenous materials and hydrothermal fluid. Antimony in coal from NW China may be influenced by the superposition of hydrothermal activity and leaching solution. Inorganic minerals (e.g., sulfide) and organic matter in coal are the determining factors for Sb enrichment in coal. The Sb isotopic fingerprint of Chinese coal is 2.46 ± 1.01 ε (weighted mean ± 1 SD, ranging from −4.45 to +9.72 ε). Accordingly, the isotopic composition of Sb in coal has great potential not only for researching Sb isotope fractionation in hydrothermal systems but also for tracing Sb release and transport in the supergene eco-environment. Furthermore, the establishment of Sb isotopic fingerprint for coal could largely reduce the uncertainty in the application of Sb isotope methods.

Leaching Behavior of the Main Metals from Copper Anode Slime during the Pretreatment Stage of the Kaldor Furnace Smelting Process

The Kaldor furnace smelting process is currently the mainstream process for treating copper anode slime, but the existence of copper, tellurium and other impurities has adverse effects on the recovery of gold and silver during the Kaldor furnace smelting stage. Therefore, it is necessary to pretreat the copper anode slime to remove these impurities before Kaldor furnace reduction smelting. However, the current pretreatment process of copper anode slime generally has the problem of low removal efficiency of copper and tellurium, and little research on the occurrence state of main metals in copper anode slime. Therefore, this study quantitatively determined the phase composition of Cu, Te, Pb, Bi, As, Sb, Se, Ag and Au, and hydrogen peroxide was introduced to enhance the leaching of impurities. The leaching behavior of each metal in copper anode slime was investigated in detail. The results demonstrate that Cu and Te in the copper anode slime mainly exist in the form of CuO and CuSO4 and Te and AuTe2, respectively. More than 99% of the Cu and 97% of the Te were leached out using 250 g/L H2SO4 and 28.8 g/L H2O2 with a leaching pressure of 0.8 MPa at 150 °C for 2 h, while the leaching of Au and Ag was both < 0.03%. The removal of Cu and Te and the enrichment of precious metals were achieved. This study provides a rich theoretical reference for the optimization of the Kaldor furnace process.

(Invited) Molecular Beam Epitaxy and Dislocation Dynamics of Metamorphic Inassb for Long-Wavelength Infrared Applications

Long-wavelength infrared (IR) III-V based devices have long been of interest for potential applications such as chemical sensing and large format IR imaging. Within the III-V family, only the InAs1-xSbx bulk alloy in composition range 0.45 ≤ x ≤ 0.8, offers the required bandgap energy (Eg ) from 100 to 125 meV at an operating temperature of 80K and below [1]. Over this composition range however, the InAs1-xSbx lattice constant varies from 6.24 to 6.39 Å, where a lack of conventional substrates has restricted progress on the growth and study of this material system. To bridge this lattice-constant gap while maintaining relatively low defect densities, we employed a metamorphic step-graded InAs1-xSbx buffer on GaSb, enabling the study of low-Eg InAs1-xSbx as a function of growth conditions. Using this method, we investigated the effect of substrate temperature (Tsub ) and group V to group III flux ratio (beam equivalent pressure, V/III) on Sb incorporation of the lowest-Eg cap layer [2]. We also used x-ray reciprocal space mapping (RSM) to examine the effect of growth conditions on strain and dislocation dynamics. Following these growth studies, we employed the metamorphic InAs1-xSbx in an InAs/InAsSb superlattice designed with a cutoff wavelength of 9 µm which leads to improved absorption compared with the lattice-matched counterpart.We first grew, via molecular beam epitaxy, several InAs1-xSbx step-graded structures in which the Sb/(As+Sb) flux ratio was varied from 0.05 to 0.50 in 0.05 increments (see figure), under various Tsub and V/III. Nomarski imaging revealed smoother surfaces under a V/III=10, the highest ratio we attempted. At this higher V/III, we observed the cross-hatch morphology expected for metamorphic materials and found that the cross-hatch spacing changes, implying a change in dislocation dynamics, with Tsub . We then used photoluminescence (PL) to measure the Sb-content in the cap layer as well as compare intensities between samples. We found the highest Sb-incorporation to occur when Tsub =415 C and V/III=10, while the most intense samples used Tsub =415-430 C and V/III=10 [2].Using RSM along [110] with (004) and (115) reflections, we identified the Sb composition in each layer. This allowed comparison of Sb-content as a function of Sb/(As+Sb) for various Tsub and V/III. The results suggest that V/III has little effect on Sb incorporation, in direct conflict with our previous PL results [2]. To understand the discrepancy between PL and RSM, we measured (004) RSM of the same three samples with the x-ray beam incident along [1-10], revealing extremely different strain relaxation compared to the [110] case (see figure). Asymmetric strain relaxation has been observed in other III-V graded buffer systems and has been explained by different dislocation formation energies and glide velocities along each direction resulting from the core structure of the dislocation being terminated with either a group-III or a group-V element [3]. Transmission electron microscopy is ongoing to further understand the dislocation dynamics in these samples.Taking this all together allowed us to investigate the effect of substrate lattice-constant on strain-balanced InAs/InAsSb superlattices designed for 9 µm cutoff wavelength [4]. Theoretically, by using a larger substrate lattice-constant the superlattice design results in larger electron-hole wavefunction overlap, ultimately increasing photon absorption. Our experimental results confirm this theory, even in the presence of increased threading dislocations inherent to the required lattice-mismatch.[1] I. Vurgaftman et al. JAP 89, 5815-5875 (2001).[2] Tomasulo et al. J. Vac. Sci. and Technol. B 36, 02D108 (2018).[3] France et al. J. Appl. Phys. 107, 103530 (2010); Gelczuk et al., J. Cryst. Growth 310, 3014 (2008).[4] Affouda, Tomasulo et al., Appl. Phys. Lett. 110, 181107 (2017). Figure 1

Electrodeposition of Cu-Based Nanofoams and Sodiophilic Metals for Highly Stable Anode-Free Sodium Batteries

Sodium-ion batteries (SIBs) represent a cost-effective and sustainable alternative to lithium-ion battery (LIBs).1 One of the main issues of SIB technology is the higher ionic radius of sodium, compared to lithium, which limits the cyclability due to unfavourable intercalation of Na+ ions into carbon-based anodes.2 Anode-free batteries represents a promising approach to improve the cyclability, changing the working principle at the anode from intercalation of Na+ ions to electrodeposition metallic sodium.3 Moreover, thanks to the anode-free configuration the energy density of the overall device can be drastically increased. To efficiently control the electrodeposition of the metallic layer of sodium, the current collector must be carefully designed. Copper nanofoams were produced by dynamic hydrogen-bubble template (DHBT) as high-surface area template for the sodium electrodeposition, as an innovative alternative to the traditionally flat electrodes. The electrodeposition of sodiophilic materials, i.e. tin and antimony, onto the nanofoam, was also investigated to control the nucleation of the metallic layer at the anode.4 Sn and Sb baths were optimized to guarantee an homogeneous distribution of the sodiophilic metal on the nanofoam. The morphology and the composition of the nanofoams was characterized and electrochemical characterization was performed in half-cell configuration, showing coulombic efficiency higher than 99% and good cyclability for 100 cycles, for both Sn and Sb compositions compared to the bare Cu. This demonstrates the feasibility of the usage of sodiophilic nanofoams as current collectors in anode-free sodium batteries. Vaalma, C., Buchholz, D., Weil, M. & Passerini, S. A cost and resource analysis of sodium-ion batteries. Nat. Rev. Mater. 2018 34 3, 1–11 (2018).Irisarri, E., Ponrouch, A. & Palacin, M. R. Review—Hard Carbon Negative Electrode Materials for Sodium-Ion Batteries. J. Electrochem. Soc. 162, A2476–A2482 (2015).Cohn, A. P. et al. Rethinking sodium-ion anodes as nucleation layers for anode-free batteries. J. Mater. Chem. A 6, 23875–23884 (2018).Seh, Z. W., Sun, J., Sun, Y. & Cui, Y. A highly reversible room-temperature sodium metal anode. ACS Cent. Sci. 1, 449–455 (2015).