Bi Content Research Articles

Characterization of Bi-doped ZnO nanorods prepared by chemical bath deposition method

This study investigates the effect of bismuth (Bi) doping on the structural, optical and electrical properties of ZnO nanorods prepared using a chemical bath deposition process. X-ray diffraction shows that the prepared nanorods are crystalline, and that Bi is successfully incorporated into the ZnO lattice. Scanning electron microscopy reveals an enhancement in the growth-rate upon Bi doping while X-ray photoelectron spectroscopy confirms the presence of Bi2O3 for Bi concentrations ≥ 2 at.%. Room temperature UV and deep-level emission peaks are observed in the as-grown ZnO nanorods. Following annealing at 573 K, in oxygen, only sharp UV luminescence peaks remain. Additinally, a blueshift in the optical band gap is observed following Bi doping. The current–voltage characteristics of the fabricated Schottky diodes show improved rectification behaviour after Bi doping. The best device is obtained at 3 at.% Bi with a Schottky barrier height and an ideality factor of 0.70 eV and 1.86, respectively.

Spin transport characteristics modulated by the GeBi interlayer in Y3Fe5O12/GeBi/Pt heterostructures

For the past few years, germanium-based semiconductor spintronics has attracted considerable interest due to its potential for integration into mainstream semiconductor technology. The main challenges in the development of modern semiconductor spintronics are the generation, detection, and manipulation of spin currents. Here, the transport characteristics of a spin current generated by spin pumping through a GeBi semiconductor barrier in Y3Fe5O12/GeBi/Pt heterostructures were investigated systematically. The effective spin-mixing conductance and inverse spin Hall voltage to quantitatively describe the spin transport characteristics were extracted. The spin-injection efficiency in the Y3Fe5O12/GeBi/Pt heterostructures is comparable to that of the Y3Fe5O12/Pt bilayer, and the inverse spin Hall voltage exponential decays with the increase in the barrier thickness. Furthermore, the band gap of the GeBi layer was tuned by changing the Bi content. The spin-injection efficiency at the YIG/semiconductor interface and the spin transportation within the semiconductor barrier are related to the band gap of the GeBi layer. Our results may be used as guidelines for the fabrication of efficient spin transmission structures and may lead to further studies on the impacts of different kinds of barrier materials.

Theoretical Study of Spontaneous Emission Spectra in GaAsBi/GaAs Quantum Wells

GaAsBi/GaAs heterojunctions have a type II band arrangement, and the band structure energy of GaAs alloys with diluted Bi content provides a wide range for designing effective band gaps. In this paper, we calculate the electronic energy band structure of GaAsBi/GaAs quantum wells (QWs) with different Bi concentrations under the 8-band K · P model. The calculated results show that the Bi concentration has a great influence on the band gap, valence band, conduction band, and other structures of GaAsBi/GaAs QWs. Based on the band structure, we make systematical simulations on the effects of different quantum well widths, different Bi concentrations, different carrier densities, and different temperatures on the spontaneous emission spectra (SES) of GaAsBi/GaAs QWs. We find that the peaks of SES reduce with the increase of temperature and well width of the quantum well structure. The full width at half maximum (FWHM) of SES at 300 K is 0.1 eV, which is much broader than that at 100 K. The increasing Bi concentration is found to give rise to the blue shift of SES. Finally, the carrier concentration in the quantum well is found to be an important factor that can enhance the SES peak values. The findings in this work are helpful in the design of GaAsBi/GaAs-based optoelectronic devices.

Bismuth exposure affects morpho-physiological performances and the ionomic profile in garden cress (Lepidium sativum L.) plants

Environmental pollution caused by heavy metals has long been considered a relevant threat to ecosystem survival and human health. The use of safer substitutes for the most toxic heavy metals in many industrial applications is discussed as a potential way to face this issue. In this regard, Bi has been proposed for replacing Pb in several production processes. However, few literature records reported on the effects of Bi on living organisms, particularly on plants. In this study, garden cress (Lepidium sativum L.) plants were exposed to different concentrations of Bi nitrate added to soil in growth chambers for 21 days. Results evidenced the toxic effect of Bi on shoot growth, regardless of the Bi nitrate concentration in the soil, paralleled by a similar reduction in the chlorophyll and carotenoid content, a decrease in the nitrogen balance index values, and an impairment of the photosynthetic machinery evaluated by chlorophyll fluorescence image analysis. The presence of Bi in the soil was shown to affect element accumulation in roots and translocation to shoots, with micronutrient content particularly reduced in the leaves of Bi-treated plants. A dose-dependent plant accumulation of Bi to metal concentration in the soil was observed, even if very low metal bioconcentration ability was highlighted. The reduced Bi translocation from roots to shoots in plants exposed to increasing Bi concentrations in the soil is discussed as a possible defense mechanism likely associated with the observed increase of anthocyan and flavonol contents and the activation of photoprotection mechanisms preventing higher damages to the photosynthetic apparatus.

Evidence of Yb3+ band broadening and continuous wave laser operation in bismuth modified KY1-x-yBixYby(WO4)2 mixed single crystals

To increase the Yb3+ optical bandwidths in highly anisotropic β:KY(WO4)2 (KYW) type laser single crystals, the simultaneous contributions of the Bi3+ 6 s2 lone electron pair and Y3+/Bi3+ ionic radii mismatch is proposed. The top seeded solution growth method with K2W2O7 as solvent was used to grow Yb doped single crystals of the KY(WO4)2/KBi(WO4)2 (KYBiW) solid solution. Crystals obtained across the used KY1xBixW solid solution range show always the low temperature β phase, with the monoclinic C2/c crystalline structure, but important differences between the Y/Bi composition of the starting solute and that of the crystal grown are found. The incorporation of Y and Yb into the crystal is preferential, resulting in a low Bi segregation coefficient, SBi= 13%, on the KYW side but near SBi= 90% in the KBiW side (Yb is still strongly incorporated filling the remaining 10%). The saturation temperature of the melt decreases as the Bi concentration in the precursor KY1-x-yBixYby(WO4)2/K2W2O7 mixture increases. Evidence of optical absorption and photoluminescence broadening of the Yb3+ bands with Bi3+ incorporation is derived from 6 K and 300 K measurements. Laser operation of KY1-x-yBixYby(WO4)2 crystals is shown to be comparable to that of KY1−yYby(WO4)2 ones. Up to ≈ 0.5 W of output power is obtained pumping in continuous wave regime with a Ti sapphire laser with slope efficiency η ≈ 65% and pump threshold< 200 mW, which is within the usual performance of KYW:Yb crystals, but the spectral distribution of the laser output in KYBiW:Yb crystals is larger than that for KYW:Yb. This spectral broadening may help in the reduction of ultrashort (fs) laser pulse duration generated by modelocking.

Templet-free one-pot synthesis of Bi-doped ZnTe nanoflowers by cation exchange method for optoelectronic applications and antibacterial activity

The present report investigates the preparation of Bi-doped ZnTe (Bi:ZnTe) nanosheets (NS) with a variation in Bi contents for different optoelectronic applications and antibacterial responses. A flower-like Bi:ZnTe NS assemblies were synthesized by a cation exchange reaction, where the average thickness of the individual NS was found to be in the range of 20–30 nm. The average thickness of the NS gradually increases with an increase in the Bi concentration. The obtained NS shows high crystallinity properties with a hexagonal ZnTe phase. With the increase in the Bi concentration, there is no significant change in either crystallinity or the phase of the NS observed. The optical properties of the as-synthesized Bi:ZnTe NS were analyzed through the UV-Vis absorbance spectra, where a variation in the absorption edge with a change in the Bi content is apparent. The optical bandgap of the material gradually increases with an increment in the Bi concentration. The photoluminescence (PL) measurement was carried out to analyze the applicability of the NS for different optoelectronic applications. Broad PL spectra for different Bi:ZnTe NS are obtained in the 520–850 nm range, with the peak around 600 nm for 532 nm excitation. Due to the non-toxic nature of the constituent elements, the Bi:ZnTe NS is favorable for biological applications. The antibacterial activities of the Bi:ZnTe NS against two pathogenic bacteria are examined, where a good antibacterial response is observed.

Structural evolution and thermoelectric properties of Mg3SbxBi2−x thin films deposited by magnetron sputtering

Mg3Bi2-based compounds are of great interest for thermoelectric applications near room temperature. Here, undoped p-type Mg3SbxBi2−x thin films were synthesized using magnetron sputtering (three elemental targets in Ar atmosphere) with a growth temperature of 200 °C on three different substrates, namely, Si as well as c- and r-sapphire. The elemental composition was measured with energy-dispersive x-ray spectroscopy and the structure by x-ray diffraction. The electrical resistivity and the Seebeck coefficient were determined under He atmosphere from room temperature to the growth temperature. All samples are crystalline exhibiting the La2O3-type crystal structure (space group P-3m1). The observed thermoelectric response is consistent with a semiconductive behavior. With increasing x, the samples become more electrically resistive due to the increasing bandgap. High Bi content (x &amp;lt; 1) is thus beneficial due to lower resistivity and a higher power factor near room temperature. Thermoelectric thin films synthesized at low temperatures may provide novel pathways to enable flexible devices on polymeric and other heat-sensitive substrates.

Icosahedral Pd Nanocrystal Catalysts with Dispersed Bi Atoms via Photochemical Route for Enhanced Formic Acid Oxidation Reaction

AbstractThe decoration of noble metal catalysts with specific main group or transition metal atoms offers an effective way to improve the catalytic performance through electronic structure regulation and active site optimization without losing the active surface area. Herein, icosahedral Pd nanocrystals catalysts with highly dispersed Bi atoms decoration have been realized by a simple photochemical reduction approach. The decoration of Bi atoms maintains the original Pd cyclic penta‐twinned structure. The deposition amount of Bi atoms, which greatly affect the catalytic performance, is fundamentally regulated by the irradiation time. Compared with pure Pd, the Pd−Bi icosahedral nanocrystals show significant improvement in electrocatalytic activity towards formic acid oxidation. Besides, the catalytic performance is correlated with the content of Bi. The optimal performance is occurred at the Bi content of 2.86%.

A phase 0/Ia study of BI 907828 concentrations in brain tissue and a nonrandomized, open-label, dose escalation study of BI 907828 in combination with radiotherapy in patients with newly diagnosed glioblastoma (GBM).

TPS2081 Background: Murine double minute 2 (MDM2) directly regulates the stability of the tumor suppressor p53, and dysregulation of this pathway can critically disrupt cellular response to genomic stress and lead to cell death. BI 907828 is a highly potent inhibitor of the MDM2-p53 interface that triggers accumulation of p53 and subsequent apoptosis in multiple GBM patient-derived xenografts (PDXs) with wild-type p53. Moreover, the combination of BI 907828 and radiotherapy provides significant survival extension in multiple orthotopic GBM PDXs. Methods: An integrated Phase 0/1 trial design is being used to evaluate the potential for BI 907828 to achieve a therapeutic concentration in brain tumor tissue and to test the safety of the combination with radiation. The co-primary endpoints for the Phase 0 study are i) measured total concentration of BI 907828 and ii) calculated unbound concentration of BI 907828 in contrast and non-contrast enhancing regions of tumor. Key inclusion criteria for the Phase 0 study are patients at least 18 years of age, ECOG performance status of 0 or 1, histologic or radiologic new diagnosis of GBM, and planned surgical resection. The first approximately 6 patients enrolled in the Phase 0 will be treated at the starting dose of 30 mg, and the future patients enrolled will be dosed at higher levels (45 mg or 60 mg) provided there are no safety concerns. If dose-limiting toxicities (DLTs) are encountered, then a Bayesian Logistic Regression Model (BLRM) with overdose control will be used to guide the dose level decisions for the additional patients. Multiple, image-registered tumor samples and intra-operative plasma samples will be analyzed for BI 907828 by LC-MS/MS. Intra-tumoral variation in BI 907828 will be correlated with pharmacodynamic effects of MDM2 inhibition (elevation of p53, p21, MDM2, GDF15, PUMA). Those patients completing the Phase 0 study and who meet additional eligibility criteria can enroll on the Phase 1a portion of the study. The pathologic inclusion criteria are TP53 wild-type, IDH1/2 wild-type, MGMT unmethylated GBM. Co-primary endpoints for the Phase 1a trial are i) occurrence of DLTs during and within 21 days after completion of radiation therapy, and ii) occurrence of adverse events throughout the treatment period. Tolerability of inter-patient dose-escalation of BI 907828 (30, 45, 60 mg) combined with radiation therapy (60 Gy in 30 fractions) will be evaluated with dose-escalation guided by a two-parameter BLRM with overdose control. Patients will remain on BI 907828 monotherapy following completion of radiotherapy until progression. To date, two patients have enrolled on the Phase 0 study, and one patient went on to enroll on the Phase 1a portion of the study. Clinical trial information: NCT05376800 .

Hot tear cracks on the suppression of Sn–Bi alloy for low-temperature assembly

PurposeIn the electronic assembly industry, low-temperature soldering holds great potential to be used in surface mounting technology. Tin–bismuth (Sn–Bi) eutectic alloys are lead-free solders applied in consumer electronics because of their low melting point, high strength and low cost. This paper aims to investigate how to address the problem of hot tear crack formation during Sn–Bi low-temperature solder (LTS) in the mass production of consumer electronics.Design/methodology/approachThis paper explored the development of hot tear cracks during Sn–Bi soldering in the fabrication of flip chip ball grid arrays. Experiments were designed to simulate various conditions encountered in Sn–Bi soldering. Quantitative analysis was conducted on the number of hot tear cracks observed in different alloy compositions and solder volumes to explore the primary cause of hot tear cracks and possible methods to suppress crack formation.FindingsHot tear cracks existed in Sn–Bi solders with different bismuth (Bi) contents, but increasing the solder volume reduced the number of hot tear cracks. Experiments were designed to test the degree of chip transient thermal warpage with temperature change, and, according to the results, glue was dispensed in specific areas to reduce chip warpage deformation. Finally, the results of combined process experiments pointed to an effective method of low-temperature soldering to suppress hot tear cracks.Research limitations/implicationsThe study focuses on Sn–Bi solders only without other solder pastes such as SAC305 or Sn–Zn series.Practical implicationsWith the growing popularity of smart electronics, especially in intelligent terminals, new energy vehicles electronics, solar photovoltaic and other field, there will be more and more demand for low- temperature, energy-saving, lead-free solders. Therefore, this study will help the industry to roll out LTS (Sn–Bi) solutions rapidly.Social implicationsIn the long term, lean and green manufacturing is expected to be essential for maintaining an advanced manufacturing industry across the world. Developing new LTSs and soldering processes is the most effective, direct solution for energy conservation and emission mitigation. With the growing popularity of smart electronics, especially in intelligent terminals, new energy vehicles and solar photovoltaics, there would be an increased demand for low-temperature, energy-saving, lead-free techniques.Originality/valueAlthough there are many methods that can be used to suppress hot tear cracks, there is little research on how to control the hot tear cracks caused by the low-temperature soldering of Sn–Bi in laptop applications. The authors studied the hot tear cracks that developed during the world’s first mass production of 50 million personal laptops based on low-temperature Sn–Bi alloy solder pastes. By controlling the Bi content, redesigning the solder paste printing process (e.g. through a printer’s stencil) and adding dispensing processes, the authors obtained reliable and stable experimental data and conclusions.

Thermal Stability of Lead-Free Transparent Cloisonné Glazes

Glazes of (70 − x) ZnO-30 B2O3-x Bi2O3 with different Bi2O3 contents were prepared by the conventional melt quench technique. Differential scanning calorimetry (DSC) curves were obtained to determine the glass transition temperature (Tg) and crystallization temperature (Tc) of the glazes. The activation energy of the glass transition (Eg) and crystallization (Ec) were calculated using the Moynihan and Kissinger models, respectively. The glass transition temperature (Tg) decreased linearly with increasing Bi2O3 content. This is because the larger Bi3+ ions reduced network connectivity and opened up the structure. The Tg increased gradually with increasing heating rate (β). This is because the higher heating rate provided more energy for the glass to transition to the liquid state. The activation energy of the glass transition (Eg) decreased with increasing Bi2O3 content. This indicates that the glass-forming ability of the system increased with increasing Bi2O3 content. The energy corresponding to the amorphous-to-crystalline transformation during nucleation and crystal growth (Ec) increased with increasing Bi content to about 30%, and then decreased above 40%. This suggests that higher Ec values have an advantage in preventing crystallization in the crystallization danger region. It can be seen that the addition of Bi2O3 in (70 − x) ZnO-30 B2O3-x Bi2O3 glazes affects the density and distribution of oxygen atoms in the glass structure. It can also be seen that the increased Bi content promotes the formation of Bi-O-Bi bonds, which act as network modifiers to reduce the number of non-cross-linked oxygen atoms and increase network connectivity.

Effect of Bi content and aging on solder joint shear properties considering strain rate

This study aims to comprehensively understand the influence of bismuth (Bi) content on the shear characteristics of solder joints under various aging conditions and strain rates. Three solder alloys were evaluated (SAC305, SAC-3Bi, and SAC-6Bi) under different aging times (0, 10, 100, and 1000 h) and shear strain rates (0.008, 0.8, and 8 s−1). The aging temperature was 150 °C. Shear tests were performed on individual solder joints using an Instron 5948 micromechanical tester at room temperature. The study developed an empirical model to determine the ultimate shear strength of SAC305 alloys as a function of aging time and strain rate, and assessed shear energy using different failure modes. Microstructural analysis was performed at various aging times to investigate the failure processes associated with each test combination. The results indicate that doping alloys with Bi improves the shear properties of alloys and mitigates the effects of aging. Furthermore, the study observed three failure mechanisms (ductile, brittle, and a combination of both) and found that Bi-containing alloys are more prone to brittle failure at relatively high shear strain rates due to high brittleness.

Preparation and antibacterial properties of bismuth-rich Bi/Bi4O5I2 photocatalytic materials with surface defects

A series of bismuth modified bismuth iodide flower-like microspheres with rich oxygen vacancies were prepared by solvothermal method. Herein, a mixed solution of propylene glycol and ethylene glycol was used as the solvent. By adjusting the ratio of these two solutions in the solvent, it is not only possible to prepare Bi4O5I2 microspheres containing different concentrations of oxygen vacancies, but also to control the content of Bi. The Bi/ Bi4O5I2 photocatalyst prepared when the ratio of propylene glycol to ethylene glycol was 5:1 in solvent showed excellent optical properties, and more than 99% of E. coli could be inactivated within 30 min under visible light irradiation. The antibacterial mechanism experiment showed that reactive oxygen species were the main substances affecting the antibacterial effect of Bi/ Bi4O5I2, and the scavenging experiment of reactive oxygen showed that •O2- was the key active substance in the antibacterial process. Finally, it was verified that reactive oxygen species can act on the interior and exterior of bacteria, indicating a more effective antibacterial pathway.

Clean and efficient recovery of In–Sn and In–Sn–Bi lead-free brazing materials by vacuum volatilization and thermodynamic modeling

In this study, a novel method was proposed for the clean and efficient recovery of high-value-added In–Sn and In–Sn–Bi alloys. Vacuum volatilization of the In–Sn binary alloy was conducted in a temperature range of 1373–1573 K with a system pressure of 5 Pa. The results showed that In and Sn were effectively separated. The Sn content in the residue was 99.9908%, and the In content in the volatile fraction reached 99.66%. Vacuum volatilization of the In–Sn–Bi ternary alloy was conducted out at 1073–1373 K and 5 Pa. The results showed that Bi could be separated from In and Sn, the Bi content in the residue decreased from 32.5% to 3.88%, and the Bi content in the volatile fraction reached 95.67%. The residual In–Sn alloy could be effectively separated by vacuum volatilization. The MIVM, M-MIVM, Wilson equation and NRTL were used to calculate and analyze the activity and activity coefficients of In–Sn, In–Bi, Sn–Bi and In–Sn–Bi alloy elements, respectively, and the results showed that M-MIVM had the highest prediction accuracy. The vapor-liquid equilibrium (VLE) data of the In–Sn, In–Bi, Sn–Bi, and In–Sn–Bi alloys were predicted, and the corresponding VLE phase diagrams were plotted based on the M-MIVM and VLE theory. The predicted VLE values were in good agreement with the corresponding experimental data determined in this study, indicating that the M-MIVM was reliable for indium-based alloys. The results of this work provided reliable experimental data and a thermodynamic model for the VLE study of In-based alloys, opening a new technique for the clean and efficient recycling of binary and multicomponent In-based alloys.

Improved photocatalytic activity under the sunlight of high transparent hydrophilic Bi-doped TiO2 thin-films

The Doping of TiO2 with various elements increases its photo-catalytic activity due to the formation of new energy levels near the conduction band. In this work, titania (TiO2) and bismuth-doped titania (Bi-doped TiO2) films were made by the sol–gel process with dip coating method employed for more cost-effective approach. The study investigated Bi-doped TiO2 films on glass substrates at different Bi concentrations (0.1, 1, 3, 5, and 7 wt%) to use as solar-photocatalysts for degradation of Rhodamine-B in the presence of Ag+, H2O2, and C3H8O3 as hole-scavengers. The film fabricated at 7 wt% Bi showed high photocatalytic activity with the addition of Ag+ as hole-scavenger, achieving 79.84%. When increasing doping Bi (from 0.1 to 7 wt%), the transmittance properties increased (from 66.27 to 97.46 %) and affected the morphology of the films structure. All films display hydrophilic characteristics with contact angles between 30° to 70°. The film of 7 wt% Bi-doped TiO2 achieved a good photocatalytic efficiency (compared to other films) at ∼ 34,65% corresponding to (101) anatase phase, 15.2 nm of crystal size, 312.5 nm of film-thickness, and 3.65 eV of bandgap energy. In the film containing 7 wt% of Bi-doped TiO2, the photocatalytic degradation of rhodamine-B was improved by approximately 14.49, 33.56, and 45.19% with the addition of C3H8O3, H2O2, and Ag+, respectively. Therefore, this work eases the fabrication of Bi-doped TiO2 thin films with high photo-catalytic activity, suggesting potential applicability in environmental applications to treat wastewater from metal ions (Ag+) and dye Rhodamine-B.

High Throughput Preparation of Bi-Sb Alloy Films for the Electrocatalytic Reduction of CO2 to Formate

Bi is considered as a highly active and selective electrocatalyst for CO2 reduction reaction (CO2RR), and Sb has great development potential. In this study, we fabricated a series of Bi-Sb alloy films by magnetron co-sputtering and further explored their electrocatalytic performances in CO2 reduction. In contrast to pure Sb catalyst, the Bi-Sb alloys substantially suppress HER and promote the pathway of CO2-to-formate. The formate selectivity increases with the increase of Bi content. When the content of Bi reaches about 40 at%, the Bi-Sb alloy exhibits the highest ability to convert CO2 to formate, and even shows a higher formate activity than that of pure Bi. Especially, the Bi45Sb55 catalyst exhibits a partial current density of formate formation of 58.0 mA cm−2 and a formate selectivity of 76.7% at −1.0 V vs RHE. A remarkable formate selectivity reaches up to over 95% in the flow cell, and a formate current density of 500 mA cm−2 is achieved at a moderate overpotential of 859 mV, exhibiting great potential for CO2RR process to practical applications. The present work could provide guidelines for the design of Bi-Sb alloy catalysts for efficient CO2RR.

Effect of growth temperature and Sb over in flux ratio on the Bi content and the surface morphology of InSbBi grown by molecular beam epitaxy

We investigated the effect of VSb/IIIIn flux ratio and growth temperature on the Bi content of InSbBi material grown on an InSb substrate using molecular beam epitaxy. The Rutherford backscattering spectrum from a bulk InSb0.977Bi0.023 epitaxial film showed a 98.5% substitutional site incorporation of Bi atoms. We demonstrated that a kinetic model of the growth can accurately predict the Bi content by taking into account the extremely low desorption/hopping probability of Sb on the InSb surface due to its low growth temperature and weaker In-Bi bond. The model implies a Bi desorption energy barrier on the InSb surface and an activation energy for Sb to displace Bi of 1.27 eV and 0.29 eV, respectively.

Raman scattering study of photoexcited plasma in GaAsBi/GaAs heterostructures: Influence of carrier confinement on photoluminescence

GaAsBi alloys are potential candidates for near-infrared optoelectronic applications, such as light-emitting diodes, laser diodes, avalanche photodiodes, and solar cells. In this paper, photoexcited plasma in GaAs1-xBix/GaAs (1.7 ≤ x ≤ 8.6%) heterostructures grown by molecular beam epitaxy was investigated using Raman spectroscopy. The strong LO phonon-plasmon coupled mode (LOPC) was generated by continuous-wave laser excitation at room temperature. The upper branch of the LOPC mode (L+ mode) was clearly observed for Bi contents from x = 3.9–8.6%, which indicates that photoexcited carriers with relatively good carrier mobility were confined in the GaAsBi/GaAs heterostructure. The photoexcited carrier density that was obtained by line shape analysis of the Raman spectra based on a dielectric model increased as the Bi content increased from 1.7 to 6.4%. This indicates that carrier overflow from the GaAsBi layer was suppressed because of the larger conduction band offset at the GaAsBi/GaAs heterointerface. In addition, the optical mobility calculated using the damping constant of the photoexcited L+ mode gradually decreased with increasing Bi content. This may be attributed to an increased defect density with decreasing growth temperature. Our findings provide valuable insight into the development of high-performance optoelectronic devices based on GaAsBi alloys and show the potential of Raman spectroscopy for evaluation of carrier confinement in heterostructures.

Enhanced thermoelectricity in Bi-sprayed bismuth sulphide particles

Bismuth sulphide (Bi2S3), an n-type semiconductor that critically demonstrates the Seebeck effect with Seebeck coefficients of about 300 μVK−1. However, its poor electrical conductivity makes it unsuitable for thermoelectric applications. In this study, we present a facile preparation method for fabricating Bi-sprayed Bi2S3 particles that alters their thermoelectric properties. Samples were created with differing Bi concentrations into the Bi2S3 compound to test for enhanced thermoelectric properties of the resulting Bi/Bi2S3 composites. The incorporation of excess Bi into Bi2S3 significantly improves the compound's electrical conductivity and optimises overall thermoelectric performance. The electrical conductivity of the Bi/Bi2S3 composites improved from 6.5 Scm−1 (for pristine Bi2S3) to 154 Scm−1 (for highest Bi added Bi2S3). Although the Seebeck coefficient of samples decreased with Bi incorporation, a high power factor (∼390 μWm−1K−2) has been achieved for an optimised composition of the composite. Incorporation of metallic Bi has led to an increase in the thermal conductivity of the samples, but the increase is not significant for the optimised composition of the composites where a high thermoelectric performance has been observed. Therefore, enhanced power factor and moderate thermal conductivity have resulted in a peak ZT value of 0.11 at room temperature. The strategy proposed here improves the thermoelectricity in Bi2S3 and shows excellent potential for developing better-performing thermoelectric compounds with excess elemental contents.

Bismuth Vacancy-Induced Enhancement of Luminescence Intensity and Irradiation Resistance for Bi4Ge3O12.

Bi4Ge3O12 (BGO) is a traditional scintillator, widely used in high-energy physics and nuclear medicine. However, it not only suffers from low scintillation intensity but also tends to be damaged by high-energy rays. Herein, we prepare pure-phase BGO materials enriched with Bi vacancies by rationally reduced Bi content, showing significantly enhanced luminescence intensity and irradiation resistance ability. The optimized Bi3.6Ge3O12 shows 178% of luminescence intensity compared to BGO. After 50 h of ultraviolet irradiation, Bi3.6Ge3O12 possesses ∼80% of original luminescence intensity, much superior to the 60% for BGO. The existence of the Bi vacancy is identified by advanced experimental and theoretical studies. The mechanism studies show the Bi vacancies could cause the symmetry destruction of the local field around the Bi3+ ion. It enhances scintillation luminescence by increasing the probability of radiative transition while resisting nonradiative relaxation caused by irradiation damage. This study initiates vacancy-induced performance enhancement for inorganic scintillators.