Since the discovery of topological insulators (TIs), there are considerable interests in demonstrating metallic surface states (SS), their shielded robust nature to the backscattering and study their ...properties at nanoscale dimensions by fabricating nanodevices. Here we address an important scientific issue related to TI whether one can clearly demonstrate the robustness of topological surface states (TSS) to the presence of disorder that does not break any fundamental symmetry. The simple straightforward method of FIB milling was used to synthesize nanowires of Bi2Se3 which we believe is an interesting route to test robustness of TSS and the obtained results are new compared to many of the earlier papers on quantum transport in TI demonstrating the robustness of metallic SS to gallium (Ga) doping. In the presence of perpendicular magnetic field, we have observed the co-existence of Shubnikov-de Haas oscillations and linear magnetoresistance (LMR), which was systematically investigated for different channel lengths, indicating the Dirac dispersive surface states. The transport properties and estimated physical parameters shown here demonstrate the robustness of SS to the fabrication tools triggering flexibility to explore new exotic quantum phenomena at nanodevice level.
Efficient storage of hydrogen is a key issue to establish hydrogen infrastructure. In the efforts of searching suitable hydrogen storage alloys, several systems have been explored so far. All of them ...suffers from some drawbacks such as low gravimetric capacity, high stability, slow sorption kinetics, etc. Lithium borohydride (LiBH4) is one of the leading contender among the hydrogen storage materials owing to its high hydrogen content of 18.5 wt%. However, its high stability needs a high operating temperature (>450 °C) for the decomposition. Recently, a thermochemical reaction between Bi2X3 and LiBH4 was observed at 120 °C while performing experiments on the anode properties of Bi2X3 (X = S, Se, & Te) for Li-ion batteries. This indicated the possibility of destabilization of LiBH4 and its low-temperature decomposition. This work presents the effect of Bi2Se3 addition to the decomposition properties of LiBH4 using XRD and XPS techniques. The first step decomposition was observed to be initiated at around 180 °C, which is much lower than 450 °C for the pristine LiBH4. A further reduction in the onset temperature is observed when the bulk Bi2Se3 is replaced by the nanosheets of this material. The mechanism of this destabilization is reported herein.
•Bi2Se3, an interesting anode material is found an impressive destabilizing agent for LiBH4.•The addition of bulk Bi2Se3 to LiBH4 reduce the onset decomposition temperature to 180 °C.•The use of Bi2Se3 nanosheets enhance the sorption kinetics further and the onset temperature is shifted to 60 °C.
Two-dimensional inorganic semiconductor materials have aroused tremendous research interest and found their potential in resolving the present urgent global issues, such as cancer therapy and fresh ...water shortage. Particularly, the near-infrared (NIR) photothermal conversion efficiency is a significant parameter in photothermal therapy. However, lack of an effective improvement strategy and their relatively low NIR phothermal conversion efficiency would restrict their wide and further application. Here, this work reports that enhanced NIR photothermal conversion is achieved in topological Bi2Se3 nanosheets by introducing a lanthanide dopant. Specifically, lanthanide Pr-doped Bi2Se3 nanosheets possess a photothermal conversion efficiency of 49.5%, which is higher than those of undoped Bi2Se3 nanosheets (31.0%) and numerous reported photothermal materials. The electronic structure of Pr-doped Bi2Se3 nanosheets was also analyzed by first-principles simulation. Furthermore, an interfacial evaporation system based on the developed nanosheets has been established, demonstrating a superior solar–thermal conversion efficiency of 91.5% and a water evaporation rate of 1.669 kg m–2 h–1 under 1 sun irradiation. The present work would provide new insights for the increase in the efficiency of photothermal materials.
•Pulsed laser deposition (PLD) using a Bi2Se2Te target.•Highly c-axis preferred-oriented Bi2Se2Te and Bi3Se2Te-dominated thin films grown by PLD.•Both Bi2Se2Te and Bi3Se2Te-dominated phase films ...exhibit similar 2D weak antilocalization.•Bi3Se2Se is likely a weak topological insulator.•The films exhibited two gigahertz acoustic phonon modes of 33.46 GHz and 61.30 GHz.
We reported a comparative study on the material–magnetotransport properties of topological insulator Bi2Se2Te and a ternary Bi3Se2Te-dominated thin films. The Bi-Se-Te thin films were grown on c-plane sapphire using pulsed laser deposition at various substrate temperatures (TS) of 180 – 300 °C. The highly c-axis-oriented films exhibited the Bi2Se2Te phase (at TS = 180, 220 °C), and a mixed phase of dominant Bi3Se2Te and mimor Bi2Se2Te (at TS = 260, 300 °C). In addition, XPS and EDS results confirmed the near stoichiometry compositions of Bi2Se2Te and Bi3Se2Te phases. In high magnetic fields, the magnetoresistance (MR) curves of Bi2Se2Te and Bi3Se2Te obeyed B2 power law, and the carrier mobility was determined to be increased monotonically from 61.3 to 86.9 cm2/Vs when TS increased from 180 to 300 °C. In low magnetic fields, MR curves of both Bi2Se2Te and Bi3Se2Te-dominated films presented two-dimensional weak antilocalization at low temperatures, possibly due to topological surface states in the thin films. Furthermore, we observed two acoustic phonon modes at 33.46 ± 0.69 GHz and 61.30 ± 1.75 GHz in both Bi2Se2Te and Bi3Se2Te-dominated thin films induced by ultrafast laser pulses.
Sulfur and Tellurium substituted Bismuth Selenide (Bi2Se3-x-ySxTey, x = y = 0, 0.1, 0.15, 0.2) quaternary alloy crystals were synthesized by using vertical Bridgman technique. Energy dispersive ...analysis of X-rays confirmed elemental composition and purity of the grown crystals. Field emission scanning electron microscopy showed that the growth of crystals has occurred by layer growth mechanism. Rhombohedral crystal structure is validated through analysis of powder X-ray diffraction pattern. Thermoelectric parameters such as electrical conductivity, Seebeck coefficient and thermal conductivity were calculated from 303 K to 773 K and from that power factor as well as figure of merit have been determined for all grown crystals. Electrical conductivity significantly increased due to Sulfur and Tellurium incorporation and maximum value obtained is 147.72 S/cm at 503 K for Bi2Se2.6S0.2Te0.2. Seebeck coefficient and thermal conductivity showed decrement with incorporation of Sulfur and Tellurium. Reduction in thermal conductivity and enhancement in electrical conductivity resulted in the improvement of figure of merit. Sulfur and Tellurium substitution showed considerable improvement in ZT from 0.31 (533 K) for pristine Bi2Se3 to 1.28 (523 K) for Bi2Se2.6S0.2Te0.2.
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•By using vertical Bridgman technique Sulfur and Tellurium substitution is done in Bismuth Selenide crystal.•Electrical conductivity showed significant enhancement with incorporation of Sulfur and Tellurium in Bi2Se3.•Peak ZT value of 1.28 at 523 K is obtained for Bi2Se2.6S0.2Te0.2, which makes it a potential thermoelectric material.•Substitution of Sulfur and Tellurium is helpful to enhance thermoelectric performance of Bi2Se3.
Herein, a one-step thermal evaporation was used for fabrication of silver bismuth selenide (AgBiSe2) thin films of various thickness. The influence of thickness on the structural, optical and ...electrical properties of AgBiSe2 thin films has been studied. The X-ray diffraction confirmed single hexagonal structure of deposited AgBiSe2 thin films. The average grain sizes D and microstrain ε of deposited AgBiSe2 films were estimated by Williamson-Hall (W-H) relation. The grain size increases from 11.52 to 29.12 nm as the thickness was increased from 150 to 550 nm, whereas strain dislocation density (ξ) and the number of crystallites N tends to decrease with thickness. The selected area electron diffraction pattern (SAED) obtained by high resolution transmission electron microscopy (HRTEM) verified the polycrystalline nature of samples and it is found to nearly agree with X-ray diffraction data. The elemental composition measurement of the as-deposited AgBiSe2 thin film showed that the as-deposited film is near stoichiometric in compound. The influence of film thickness on the optical parameters of the AgBiSe2 thin films, such as refractive index n, extinction coefficient k, real dielectric ε1, imaginary dielectric constant ε2, skin depth and the optical band gap, Eg has been studied. It is found that the values of energy gap decrease from 1.88 to 1.68 eV with increasing thickness, while the values of Urbach energy follow an opposite trend. The electrical conductivity was measured by four-probe experiment in the range from 300 to 500 K. The analysis of dc conductivity data revealed the presence of two distinct regions with two various slopes confirming the transformation from hexagonal phase to rhombohedral phase at about 460 K.
•AgBiSe2 thin films of various thicknesses were deposited by thermal evaporation.•XRD and HRTEM show that films formed in a pure single hexagonal structure.•The thresholding image displays the gradual increase of grain size with thickness.•The band gap energies changed from 1.88 to 1.68 eV with increasing thickness.•Dc conductivity confirms the transformation from hexagonal to rhombohedral phase at 460 °C.
In the last few years, research based on topological insulators (TIs) has been of great interest due to their intrinsic exotic fundamental properties and potential applications such as quantum ...computers or spintronics. The fabrication of TI nanodevices and the study of their transport properties has mostly focused on high quality crystalline nanowires or nanoribbons. Here, we report a robust approach to Bi2Se3 nanowire formation from deposited flakes using an ion beam milling method. Fabricated Bi2Se3 nanowire devices were employed to investigate the robustness of the topological surface state (TSS) to gallium ion doping and any deformation in the material due to the fabrication tools. We report on the quantum oscillations in magnetoresistance (MR) curves under the parallel magnetic field. The resistance versus magnetic field curves are studied and compared with Aharonov-Bohm (AB) interference effects, which further demonstrate transport through the TSS. The fabrication route and observed electronic transport properties indicate clear quantum oscillations, and these can be exploited further in studying the exotic electronic properties associated with TI-based nanodevices.
•Kelly and Dip-type sidebands soliton pulse in an Erbium-doped fiber laser cavity Bi2Te3 saturable absorber.•Topological insulator-based Bi2Te3 saturable absorber fabricated using optical deposition ...method.•High modulation depth of about 41.4% with high linear transmission of about 91% achieved.•Conventional Kelly sidebands soliton with repetition rate of 24 MHz and pulse width of 0.78 ps recorded.•Dip-peak intensity soliton sidebands with 13.5 MHz observed at maximum available pump power of 176 mW.
Conventional Kelly sidebands soliton and dip-type sidebands soliton were observed with the employment of Bi2Te3 as saturable absorber (SA) in Erbium-Doped Fiber Laser (EDFL). The fabricated Bi2Te3 possessed the following characteristics: Isat 102 MW/cm2, modulation depth 41.4%, and non-saturable absorption at 10%. The Bi2Te3 solution was transferred to the end of the fiber ferrule by the optical deposition method. Conventional Kelly sidebands soliton was obtained with a fundamental repetition rate and pulse width of 24 MHz and 0.78 ps, respectively. The existing cavity length was extended and with the appropriate tuning of light polarization, dip-peak intensity soliton sidebands with bunched pulses were observed. The oscillation trace revealed the repetition rate of dip-peak intensity sidebands soliton was ascertained at 13.5 MHz, which was in accordance with the cavity length. There was a total of 144 pulses in a single bunch envelope under the maximum available pump power. With the appropriate tuning of light polarization, constructive and destructive interference between soliton and dispersive waves took place in EDFL resulting in the formation of peak intensity (Kelly sidebands) and dip-peak intensity on the soliton spectrum. To the best of the author’s knowledge, this is the first demonstration of dip-peak intensity sidebands soliton using Bi2Te3.
A newly developed electrochemical biosensor composed of a topological insulator (TI) and metallic DNA (mDNA) is fabricated. The bismuth selenide nanoparticle (Bi2Se3 NP) is synthesized and sandwiched ...between the gold electrode and another Au‐deposited thin layer (Bi2Se3@Au). Then, eight‐silver‐ion mediated double‐stranded DNA (mDNA) is immobilized onto the substrate (Bi2Se3@Au‐mDNA) for the further detection of hydrogen peroxide. The Bi2Se3 NP acts as the electrochemical‐signal booster, while unprecedentedly its encapsulation by the Au thin layer keeps the TI surface states protected, improves its electrochemical‐signal stability and provides an excellent platform for the subsequent covalent immobilization of the mDNA through Au–thiol interaction. Electrochemical results show that the fabricated biosensor represents much higher Ag+ redox current (≈10 times) than those electrodes prepared without Bi2Se3@Au. The characterization of the Bi2Se3@Au‐mDNA film is confirmed by atomic force microscopy, scanning tunneling microscopy, and cyclic voltammetry. The proposed biosensor shows a dynamic range of 00.10 × 10−6m to 27.30 × 10−6m, very low detection limit (10 × 10−9m), unique current response (1.6 s), sound H2O2 recovery in serum, and substantial capability to classify two breast cancer subtypes (MCF‐7 and MDA‐MB‐231) based on their difference in the H2O2 generation, offering potential applications in the biomedicine and pharmacology fields.
Bi2Se3 nanoparticle encapsulated between the two layers of gold, owing to its unique electrical properties, is found to enhance the electrochemical signal of silver ion intercalated inside the DNA helix and increase the signal‐to‐noise ratio of the proposed biosensor. The Bi2Se3@Au‐mDNA biosensor offers an unrivaled current response (1.6 s) and a low limit of detection (10 × 10−9m).
Josephson junctions with topological insulators as their weak link (S–TI–S junctions) are predicted to host Majorana fermions, which are key to creating qubits for topologically protected quantum ...computing. But the details of the S–TI–S current-phase relation and its interplay with magnetic fields are not well understood. We fabricate a Bi2Se3 junction with NbTi leads and measure the Fraunhofer patterns of the junction with applied in-plane fields. We observe that asymmetric Fraunhofer patterns appear in the resistance maps of Bz vs Bx,y, with aperiodic node spacings. These asymmetric patterns appear even at zero parallel field and for temperatures up to 1 K. The anomalous features are compared to asymmetric Fraunhofer patterns expected for finite Cooper pair momentum shifts as well as geometric effects. We show that the geometric effects can dominate, independent of in-plane field magnitude. Furthermore, these results are important for differentiating geometrical phase shifts from those caused by Cooper pair momentum shifting, Majorana mode signatures, or other unconventional superconducting behavior.
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