Sb Composition Research Articles

Growth interruption strategies for interface optimization in GaAsSb/GaAsN type-II superlattices

Recently, GaAsSb/GaAsN type II short-period superlattices (SLs) have been proposed as suitable structures to be implemented in the optimal design of monolithic multi-junction solar cells. However, due to strong surface Sb segregation, experimental Sb composition profiles differ greatly from the nominal square-wave design. In this work, the improvement of the interface quality of these SLs in terms of compositional abruptness and surface roughness has been evaluated by implementing different growth interruption times under Sb4/As4 (soaking) and As4 (desorption) overpressure conditions before and after the growth of GaAsSb layers, respectively. The combined effects of both processes enhance Sb distribution, achieving squarer compositional profiles with reduced surface roughness interfaces. It has been found that the improvement in compositional abruptness is quantitatively much higher at the lower interface, during soaking, than at the upper interface during desorption. Conversely, a larger decrease in surface roughness is achieved at the upper interface than at the lower interface. Fitting of the Sb segregation profiles using the 3-layer kinetic fluid model has shown that the increase in Sb incorporation rate is due to the decrease in segregation energy, presumably to changes in the surface reconstruction of the floating layer at the surface.

Bulk InAsSb-based upside-down pCBn photodetectors with greater than 5 µm cut-off wavelength

The InAsSb-based photodetectors covering the whole mid-infrared wavelength at 150 K have been modeled, successfully fabricated, and characterized. In this work, we increased the Sb composition in InAs1−xSbx to extend the cut-off wavelength; simultaneously, the novel upside-down structure was adopted to decrease the dark current to ensure good performance of the device at high operating temperature. The growth sequence of the upside-down InAs0.81Sb0.19/AlAsSb material system was reversed to the conventional nBn structure, and the AlSb/AlAs0.08Sb0.92 electron compound barrier was grown before the InAs0.81Sb0.19 active layer. At 150 K and 0.8 V forward bias, the fabricated photodetector demonstrates a dark current density around 3.46 × 10−4 A/cm2, a peak responsivity up to 1.89 A/W, and a quantum efficiency up to 56% at 4.2 µm, corresponding to 1.23 × 1011 cm Hz1/2/W detectivity.

Optical Investigation of p-GaAs/i-GaN0.38yAs1-1.38ySby/n-GaAs Quantum Wells Emitters

We have studied the 1.55 μm optical properties of p-GaAs/i-GaN0.38yAs1-1.38ySby/n-GaAs quantum wells using a self-consistent calculation combined with the anticrossing model. We have found that the increase of injected carriers’ density induces the increase of optical gain and radiative current density. The rise of doping density causes a blue shift of the fundamental transition energy accompanied with significant increase of optical gain. The quantum-confined Stark effect on radiative current density is also studied. The variation of radiative current as function of well width and Sb composition is also examined. In order to operate the emission wavelength at the optical fiber telecommunication domain, we have adjusted the well parameters of p-GaAs/i-GaN0.38yAs1-1.38ySby/n-GaAs.

The Dependence of InAs/InAsSb Superlattice Detectors’ Spectral Response on Molecular Beam Epitaxy Growth Temperature

In this paper, we report on the influence of molecular beam epitaxial (MBE) growth temperature on the spectral response of the long-wavelength infrared radiation (LWIR), three-stage thermoelectrically (TE) cooled (T = 210, 230 K) InAs/InAsSb type-II superlattice (T2SL)-based detectors grown on the GaSb/GaAs buffer layers/substrates. Likewise, antimony (Sb) composition and the superlattice (SL) period could be used for spectral response selection. The presented results indicate that the growth temperature affects the 50% cut-off (λ50%cut-off) of the fabricated devices and could be used for operating wavelength tunning. Assuming constant Sb composition and T2SL period during MBE process, the growth temperature is presented to influence λ50%cut-off covering entire LWIR (e.g., temperature growth change within the range of 400–450 °C contributes to the λ50%cut-off ~ 11.6–8.3 μm estimated for operating temperature, T = 230 K). An increase in temperature growth makes a blueshift of the λ50%cut-off, and this is postulated to be a consequence of a modification of the SL interfaces. These results show an approach to the T2SL InAs/InAsSb deposition optimization by the growth temperature in terms of the spectral response, without influencing the T2SLs’ structural properties (Sb composition, SL period).

Phase transitions in thermoelectric Mg-Ag-Sb thin films

α-MgAgSb thin films are expected to be compatible with the complementary metal oxide semiconductor (CMOS) technology, and could be used to develop thermoelectric modules integrated to microelectronic devices for energy harvesting. However, bulk studies showed that the presence of secondary phases in addition to α-MgAgSb, such as the metallic phase Ag3Sb, deteriorates the thermoelectric properties. Consequently, understanding phase transformations in Mg-Ag-Sb thin films produced by CMOS-compatible magnetron sputtering is capital for the production of homogeneous α-MgAgSb thin films to be used in energy harvesting thermoelectric modules integrated into microelectronic devices. In this work, different Mg-Ag-Sb films were deposited by magnetron sputtering using either a single alloyed target with the average composition Mg1/3Ag1/3Sb1/3 or using Mg, Ag, Sb co-deposition from three elementary targets. In situ X-ray diffraction measurements were used to investigate the phase transitions in the films, aiming to determine the thermal stability of α-MgAgSb and to investigate the possibility of producing α-MgAgSb films without secondary phases. The results show that the use of the single alloyed target does not allow the production of homogenous α-MgAgSb films. The phase formation sequence observed in the films is different from bulk samples in this case. Co-sputtering of the three elements Mg, Ag, and Sb, allowing the composition of the as-deposited film to be better controlled, confirmed that the Mg1/3Ag1/3Sb1/3 stoichiometry does not allow the production of homogenous α-MgAgSb films. Contrasting with usual belief, the results show that the Ag and Sb compositions of the phases α-MgAgSb and γ-MgAgSb vary during annealing, and the phase transitions α-to-β, β-to-γ, and α-to-γ are not allotropic. These finding are of major importance for the production of the thermoelectric compound α-MgAgSb, and explain the large variations of the α-MgAgSb Seebeck coefficient reported in the literature.

Solvothermal synthesis of nanosized cobalt antimonide for thermoelectrics

The present paper highlights the synthesis of cobalt antimonide (CoSb3) micro/nanostructures by following solvothermal technique with water as solvent. Recipe is optimized for preparation of refined CoSb3 compounds and demonstrated that a high processing temperature of 500 °C and long duration of 72 hr indicates presence of CoSb3 phase. The microstructures and composition of the as synthesized CoSb3 nanocomposites are characterized to achieve the optimized phase. The morphologies as imaged using field emission scanning electron microscope resemble granules for the as-synthesized CoSb3. The phase purity and crystallographic structure of the as-synthesized CoSb3 nanocomposites as determined by XRD indicates the formation of the cubic phase of CoSb3 and agrees well with the JCPDS data mentioned for the highly pure CoSb3. The EDX estimates the elemental composition of Co and Sb in 1:3 stoichiometric ratio for the as-synthesized CoSb3. The currently prepared nanosized skutterudite CoSb3 material synthesized by solvothermal method could be utilized as active material for the development of highly efficient thermoelectric devices. Copyright © 2018 VBRI Press.

Analisis Signifikansi Roda Skateboard Berbahan Komposit Serbuk Batang Pisang Terhadap Perfoma Kecepatan Dengan Metode Anova

In general, skateboard wheels are made from a mixture of polyurethane (PU) so that they are elastic, lightweight, and strong. However, this material is classified as a toxic material, difficult to obtain, and the price is relatively expensive. Therefore, alternative raw materials that are more environmentally friendly, non-toxic, easy to find, and have sufficient availability are needed. Banana trees are the most abundant and easily found plants in Indonesia , especially Medan . This tree has a soft structure and absorbs vibrations. Thus, the research was conducted to obtain the characteristics of skateboard wheel products from banana stem powder (SBP) composite material as an alternative raw material. The purpose of this study was to analyze the speed of skateboards made of PU (commercial) and SB P in order to obtain the optimum composition of SB P for the manufacture of skateboard wheels. The test uses a sliding platform with a slope of 30 o against a flat plane. The number of variations consists of the composition of SB P 5%, 10%, and 15%. As a control, commercial PU wheels were also tested. Analysis of data using the analysis method of mean variation (ANOVA) with the condition of acceptance of the hypothesis H 0 at a <0.05. The results obtained are that there is an increase in the speed of skateboards made of SB P composite up to 6, 85% compared to commercial wheels. Based on the Anova test results, it was found that the application of SB P composite materials as raw material for skateboard wheels was proven to significantly increase the speed performance of these wheels.

Ultralow Power Magnetization Switching by Non‐Epitaxial Topological Insulator‐Generated Spin–Orbit Torque

Topological insulators (TIs) with large spin Hall effect have potential applications for ultralow power consumption spintronic devices. However, the present methods for fabricating TIs mainly rely on epitaxial methods, which limits their mass production. Herein, perpendicular magnetized Pt/Co/(Bi1–x Sb x )2Te3 (BST) heterostructures are prepared to measure the spin–orbit torque efficiency of BST fabricated by the conventional magnetron sputtering method, which shows large‐scale wafer production ability. The Fermi levels and the topological surface states (TSSs) are modulated by the composition of Sb in BST. The effective damping‐like spin Hall angle (θ ) is independent of the thickness of TIs. When the Fermi level is near the Dirac point, θ for these non‐epitaxial heterostructures reaches its maximum value around 0.77, which is much larger than that of traditional ferromagnetic/heavy metal (FM/HM) heterostructures and quite close to that of the epitaxial TIs. This indicates that the TSS has the dominant contribution to θ . The large θ results in the small critical current density (J c ≈ 105 A cm−2) for fully switching the magnetization of Co, compared with FM/HM heterostructures with J c around 107 A cm−2. This work paves the way for potential large‐scale spintronic devices using low energy consumption non‐epitaxial TIs.

Room temperature ferromagnetism in Sb doped ZnO

Using first-principle calculations, the magnetic properties of the monovacancies and the Sb-related defects including VZn, VO, SbZn, SbO, SbZn-VZn and SbZn-2VZn are studied. It is found that the isolated VZn with the charge state of 0 and −1 can contribute to ferromagnetism in ZnO material. The substitution of Sb on O sites (SbO0) also results in magnetic property. Moreover, the SbZn-2VZn complex is another defect having non-zero magnetic moment and energetically favors for the ferromagnetic state. The resultant density of states (DOS) and spin density distribution clearly show that the ferromagnetic interaction is majorly due to the O-p Zn-d and Sb-p states. To check this calculation, Sb-doped ZnO samples were grown by pulsed laser deposition with different Sb composition under P(O2) = 1.3 Pa. SQUID study showed that all of these samples are ferromagnetic at room temperature. The variation of the saturation magnetization against the Sb composition is discussed.

Study of patterned GaAsSbN nanowires using sigmoidal model

This study presents the first report on patterned nanowires (NWs) of dilute nitride GaAsSbN on p-Si (111) substrates by self-catalyzed plasma-assisted molecular beam epitaxy. Patterned NW array with GaAsSbN of Sb composition of 3% as a stem provided the best yield of vertical NWs. Large bandgap tuning of ~ 75 meV, as ascertained from 4 K photoluminescence (PL), over a pitch length variation of 200–1200 nm has been demonstrated. Pitch-dependent axial and radial growth rates show a logistic sigmoidal growth trend different from those commonly observed in other patterned non-nitride III–V NWs. The sigmoidal fitting provides further insight into the PL spectral shift arising from differences in Sb and N incorporation from pitch induced variation in secondary fluxes. Results indicate that sigmoidal fitting can be a potent tool for designing patterned NW arrays of optimal pitch length for dilute nitrides and other highly mismatched alloys and heterostructures.

Ultrafast scattering dynamics of coherent phonons in Bi1−x Sb x in the Weyl semimetal phase

We investigate ultrafast phonon dynamics in the Bi1−x Sb x alloy system for various compositions x using a reflective femtosecond pump-probe technique. The coherent optical phonons corresponding to the A1g local vibrational modes of Bi–Bi, Bi–Sb, and Sb–Sb are generated and observed in the time domain with a few picoseconds dephasing time. The frequencies of the coherent optical phonons were found to change as the Sb composition x was varied, and more importantly, the relaxation time of those phonon modes was dramatically reduced for x values in the range 0.5–0.8. We argue that the phonon relaxation dynamics are not simply governed by alloy scattering, but are significantly modified by anharmonic phonon–phonon scattering with implied minor contributions from electron–phonon scattering in a Weyl-semimetal phase.

Dilute-antimonide GaSbN/GaN dots-in-wire heterostructures grown by molecular beam epitaxy: Structural and optical properties

We have investigated the epitaxy of GaSbN/GaN dots-in-wire heterostructures on a Si substrate by plasma-assisted molecular beam epitaxy. The photoluminescence (PL) emission wavelength was tuned from UV to blue and green regions at room temperature by varying the antimony (Sb) composition in the dilute regime (Sb concentration &amp;lt; 1%). Structural analysis reveals clearly defined interfaces between quantum-confined crystalline GaSbN and GaN layers with negligible lattice mismatch. The PL spectra unveil the non-monotonic dependence of the peak energy and linewidth on the excitation power and temperature. This can be correlated with the contributions from both localized and free excitons, wherein localized states dominate at low temperature and low excitation power. The screening of the quantum-confined Stark effect in the electroluminescence measurement suggests the presence of a substantially weaker built-in electric field (&amp;lt;240 kV/cm) for the green light emission at an ∼531 nm wavelength compared to conventional InGaN/GaN quantum wells, which is attributed to significantly reduced lattice mismatch between dilute-Sb GaSbN and GaN.

Sb-based intermetallics and nanocomposites as stable and fast Na-ion battery anodes

To achieve high-performance Sb-based anodes for Na-ion battery (NIB), various approaches for obtaining amorphous C-containing Sb composite (Sb@C), Sb-based intermetallic compounds (TiSb2 and NbSb2), and Na-inactive metal carbide and amorphous C-containing Sb composites (Sb@TiC@C and Sb@NbC@C) have been introduced. First, Sb@C was prepared using a simple solid-state ball-milling, and then its potential as a NIB anode material was investigated. The electrochemical phase change mechanism of Sb during the sodiation/desodiation of Sb@C was investigated using various ex situ analytical techniques. Sb was found to sequentially transform into NaSb and Na3Sb during sodiation and NaSb and Sb during desodiation. Second, as another trial to further improve the electrochemical performance of Sb, Sb-based intermetallic compounds of TiSb2 and NbSb2 were synthesized by alloying reaction via a simple solid state heat-treatment and their potential as NIB anode materials was investigated. Lastly, the Sb@TiC@C and Sb@NbC@C nanocomposites comprising tiny (~3–5 nm) Sb nanocrystallites and Na-inactive metal carbide (TiC/NbC) matrix embedded in buffering amorphous C were synthesized by alloying and dealloying reaction. The Sb@TiC@C and Sb@NbC@C demonstrated highly reversible, stable capacity (Sb@TiC@C: 746 mAh cm−3, Sb/NbC/C: 726 mAh cm−3 after 100 cycles) and fast rate capability with exceptional capacity retentions after 400 cycles (Sb@TiC@C: ~710 mAh cm−3 at 2 C rate, Sb@NbC@C: ~680 mAh cm−3 at 2 C rate). Therefore, the Sb-based nanocomposites synthesized by alloying and dealloying are considered to be possible new anode materials for use in high-performance NIBs.

Effect of Sb composition on the band alignment of InAs/GaAsSb quantum dots* *Project supported by the National Key Research and Development Program of China (Grant Nos. 2019YFB1503601 and 2017YFB0405302), the National Natural Science Foundation of China (Grant Nos. 61574139 and U1738114), and the Strategic Priority Research Program on Space Science, the Chinese Academy of Sciences (Grant No. XDA15051200).

Aiming to achieve InAs quantum dots (QDs) with a long carrier lifetime, the effects of Sb component in cap layers on the band alignment of the InAs/GaAsSb QDs have been studied. InAs QDs with high density and uniformity have been grown by molecular beam epitaxy. With increasing Sb composition, the InAs/GaAsSb QDs exhibit a significant red-shift and broadening photoluminescence (PL). With a high Sb component of 22%, the longest wavelength emission of the InAs/GaAs0.78Sb0.22 QDs occurs at 1.5 μm at room temperature. The power-dependence PL measurements indicate that with a low Sb component of 14%, the InAs/GaAs0.86Sb0.14 QDs have a type-I and a type-II carrier recombination processes, respectively. With a high Sb component of 22%, the InAs/GaAs0.78Sb0.22 QDs have a pure type-II band alignment, with three type-II carrier recombination processes. Extracted from time-resolved PL decay traces, the carrier lifetime of the InAs/GaAs0.78Sb0.22 QDs reaches 16.86 ns, which is much longer than that of the InAs/GaAs0.86Sb0.14 QDs (2.07 ns). These results obtained here are meaningful to realize high conversion efficiency intermediate-band QD solar cells and other opto-electronic device.

The role of As species in self-catalyzed growth of GaAs and GaAsSb nanowires

Precise control and broad tunability of the growth parameters are essential in engineering the optical and electrical properties of semiconductor nanowires (NWs) to make them suitable for practical applications. To this end, we report the effect of As species, namely As2 and As4, on the growth of self-catalyzed GaAs based NWs. The role of As species is further studied in the presence of Te as n-type dopant in GaAs NWs and Sb as an additional group V element to form GaAsSb NWs. Using As4 enhances the growth of NWs in the axial direction over a wide range of growth parameters and diminishes the tendency of Te and Sb to reduce the NW aspect ratio. By extending the axial growth parameter window, As4 allows growth of GaAsSb NWs with up to 47% in Sb composition. On the other hand, As2 favors sidewall growth which enhances the growth in the radial direction. Thus, the selection of As species is critical for tuning not only the NW dimensions, but also the incorporation mechanisms of dopants and ternary elements. Moreover, the commonly observed dependence of twinning on Te and Sb remains unaffected by the As species. By exploiting the extended growth window associated with the use of As4, enhanced Sb incorporation and optical emission up to 1400 nm wavelength range is demonstrated. This wavelength corresponds to the telecom E-band, which opens new prospects for this NW material system in future telecom applications while simultaneously enabling their integration to the silicon photonics platform.

Ab-initio study of ordered III–V antimony-based semiconductor alloys $$\mathbf{GaP }_{1-x}{} \mathbf{Sb} _{x} \mathbf{and} AlP _{1-x}{} \mathbf{Sb} _{x}$$

In this work, we have investigated the structural, electronic and thermodynamic properties of GaP $$_{1-x}$$ Sb $$_{x}$$ and AlP $$_{1-x}$$ Sb $$_{x}$$ ternary alloys for a number of ordered structures and compositions in a series of first-principles calculations within the density functional theory, using full potential-linearised augmented plane-wave (FP-LAPW) method, as implemented in the WIEN2k code. The exchange-correlation effect was treated within the generalised gradient approximation (GGA) in the form of GGA-PBEsol to optimise the structure and to compute the ground-state properties. In addition to the GGA, the modified Becke–Johnson (mBJ) potential coupled with the spin-orbit interaction (SOI) was also applied to obtain reliable results for the electronic properties. Our investigation on the effect of composition on lattice constant, bulk modulus and band gap showed almost nonlinear dependence on the composition. The GaP $$_{1-x}$$ Sb $$_{x}$$ and AlP $$_{1-x}$$ Sb $$_{x}$$ alloys are found to be semiconductors with a positive energy gap for the whole concentration range. The spin-orbit splitting $$\Delta _{\mathrm {SO}}$$ was found to increase with Sb composition with a marginal bowing parameter. Besides, a regular-solution model was used to investigate the thermodynamic stability of the alloys which mainly indicates a phase miscibility gap. In addition, the quasiharmonic Debye model was applied to analyse the effect of temperature and pressure on the Debye temperature and heat capacity.

Influence of quantum dot morphology on the optical properties of GaSb/GaAs multilayers

We examine the influence of quantum dot (QD) morphology on the optical properties of two-dimensional (2D) GaSb/GaAs multilayers, with and without three-dimensional nanostructures. Using nanostructure sizes from scanning transmission electron microscopy and local Sb compositions from local-electrode atom-probe tomography as input into self-consistent Schrödinger–Poisson simulations based on 8 × 8 k·p theory, we compute confinement energies for QDs, circular arrangements of smaller QDs, termed QD-rings, and 2D layers on GaAs substrates. The computed confinement energies and the measured photoluminescence emission energies increase from QDs to QD-rings to 2D layers, enabling direct association of nanostructure morphologies with the optical properties of the GaSb/GaAs multilayers. This work opens up opportunities for tailoring near to far infrared optoelectronic devices by varying the QD morphology.

The origin of additional modes in Raman spectra of ZnO:Sb films

Systematic Raman spectroscopic study was conducted on the wurtzite (002) Sb-doped ZnO films grown by pulsed laser deposition with different Sb doping levels and annealed at different temperatures, with the undoped, Cu-doped and Ga-doped ZnO films for comparison. Three additional Raman modes 235 cm−1, 510 cm−1 and 534 cm−1 were observed only in the Sb-doped ZnO samples but not in the other controls. The vibration mode 235 cm−1was associated with the SbZn-related shallow donor, which was the origin of the n+-conductivity. The 510 cm−1 vibrational mode has been associated with HO in previous literature. However in the current study, the correlation between its intensity and the H abundance was not observed. The 534 cm−1 Raman mode was associated with a Sb-related defect. The variation of the intensities of the Raman modes 235 cm−1 and 510 cm−1 upon annealing and change of Sb composition were discussed.

Compound semiconducting SnSb alloy anodes for Li ion batteries: effect of elemental composition of Sn–Sb

Compound semiconducting alloy SnSb anodes have been prepared in three different compositions, SnxSby (x = 2–4; y = 3–5) by regular and microwave assisted co-precipitation techniques. Preliminary structural analysis reveals that all the Sn–Sb alloy systems fall into the hexagonal symmetry which is confirmed by the Rietveld refined XRD patterns, SAED pattern and Raman analyses. Increasing the Sn to Sb ratio provides better stoichiometry in SnxSby alloy system which is ensured with EDX analysis. This is further superior in the case of microwave treated SnxSby nanoparticles. Cyclic voltammetry analysis provides augmented redox reactions when increasing the Sn–Sb composition. On the whole, highly crystalline Sn4Sb5 sample treated in microwave radiation exhibit better electrochemical and electrical properties. The diffusion co-efficient of SnxSby nanoparticles lies the range of 10–11–10–12 cm2 s−1. Among all, specific capacity of the Sn4Sb5 treated in microwave radiation is highly stable and provides the highest value in the range ∼153 mAh g−1 for 50 cycles in the aqueous based electrochemical system. Similarly, this sample delivers the highest electrical conductivity in the range of 4.54 × 10–4 S cm−1. Such a behavior is expected to possess better rate capability and reversibility thereby fulfilling the requirements of a successful anodic component in both aqueous/non-aqueous Li-on batteries.

A Thermoelectrically Cooled nBn Type‐II Superlattices InAs/InAsSb/B‐AlAsSb Mid‐Wave Infrared Detector

Herein, an nBn barrier mid‐wave infrared InAs/InAsSb (xSb = 0.4) type‐II superlattice (T2SL) detector operating in the thermoelectrical (TE) cooling condition is reported. AlAsSb (Sb‐composition, xSb ≥ 0.975) is shown not to introduce an additional barrier in the valence band in the analyzed temperature range (≥200 K) reached by four‐stage TE cooling in nBn barrier architectures with a T2SL InAs/InAsSb active layer. The dark current and photocurrent produced are analyzed in relation to the barrier and contact layer doping, with the Sb composition of the barrier indicating the optimal architecture. The results of the simulation are compared with the experimental results of the HgCdTe and InAsSb nBn barrier detectors. A detectivity of ≈1010 cmHz1/2 W−1 at 200 K is reported without an immersion lens (≈1011 cmHz1/2 W−1 is reported for an immersed detector).