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Growth, morphology and crystal structure of electrodeposited Bi2Se3 films: Influence of the substrate
摘要： In this study, we investigated the growth, morphology and crystal structure of electrodeposited Bi2Se3 films on n-Si, Au and Ru substrates. The range of potentials at which films with good quality and stoichiometry can be grown have been identified. Scanning electron micrographs of the early stages of nucleation and growth suggests the film formation on all three substrates follow the Volmer-Weber growth mode. In the case of Si substrate, a pure orthorhombic phase of Bi2Se3 could be grown which is influenced by the epitaxy of the Si substrate. The Faradaic efficiency of film growth on Si substrate was found to be around 90%. However, on Au and Ru substrates, growth of mainly the rhombohedral phase could be achieved having relatively lower Faradaic efficiencies of 68% and 78%, respectively. The Bi2Se3 films grown on Au at more negative potentials were found to exhibit improvements in the rhombohedral crystal phase. Low temperature annealing was found to transform the orthorhombic or mixed phase crystal structure to that of pure rhombohedral. The onset of phase transformation in the mixed phase Bi2Se3 films (on Au) was found to be around 125°C, determined using in-situ Raman spectroscopy. Aside from the temperature, the duration of heat treatment is identified to play a crucial role in this phase transformation. Based on our findings on room temperature deposition, we conclude that the growth of pure orthorhombic phase is favored on Si, while on Au and Ru, growth of the rhombohedral or mixed phase of Bi2Se3 could be achieved.
关键词： Raman,Annealing,Electrodeposition,Crystal structure,Substrate epitaxy,Bi2Se3,Growth
更新于2025-09-23 15:23:52
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Experimental Observation of Bound States of 2D Dirac Electrons at Surface Steps of the Topological Insulator Bi <sub/>2</sub> Se <sub/>3</sub>
摘要： Topologically protected surface states of three-dimensional topological insulators provide a model framework for studying massless Dirac electrons in two dimensions. Usually a step on the surface of a topological insulator is treated as a scatterer for the Dirac electrons, and the study of its effect is focused on the interference of the incident and scattered electrons. Then a major role plays the warping of the Dirac cone far from the Dirac point. The existence of another significant effect near the Dirac point brought about by the presence of steps is experimentally demonstrated here. Namely the band bending in the vicinity of steps leads to formation of 1D bound states in the corresponding potential wells. The observation of bound states in such potential wells in our scanning tunneling microscopy and spectroscopy investigation of the surface of the topological insulator Bi2Se3 is reported. Numerical simulations support our conclusion and provide a recipe for the identification of such states.
关键词： density of states,Dirac electrons,surface states,edge states,bound states,scanning tunneling microscopy,Bi2Se3,topological insulators,scanning tunneling spectroscopy
更新于2025-09-23 15:23:52
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Photo and thermal induced Bi2Se3 formation from Bi/GeSe2 hetero junction layer for topological insulator
摘要： In the present paper, we report the evolution of Bi2Se3 topological phase from the Bi diffusion into GeSe2 layer in the Bi/GeSe2 hetero junction film with light and thermal energy. The photo and thermal induced changes in the structural and optical properties of thermally evaporated Bi/GeSe2 bilayer film has been studied by various characterization techniques. The amorphous to crystalline phase transition and the formation of Bi2Se3 topological phase was confirmed from the X-ray diffraction analysis. The deposition as well as diffusion of Bi into GeSe2 layer changed the optical constants like transmitivity, absorption power, optical band gap, Urbach energy, Tauc parameter as studied from UV–Vis–NIR spectroscopy. The transmission power decreased after thermal annealing and laser irradiation where the reverse effect was found in case of absorption coefficient. The optical band gap decreased after diffusion which can be explained on the basis of density of defect states with an increase in disorder. Scanning electron microscopy investigations showed that the surface morphology was influenced by the diffusion phenomena. The Raman analysis also confirms the Bi2Se3 phase evolution with appropriate vibrational peaks. The modifications in optical parameters with thermal and light induced diffusion can be used in various optical applications using such metal/chalcogenides heterojunction layers.
关键词： Amorphous materials,Optical properties,Bi2Se3 phase,Chalcogenides,Thin films,Band gap
更新于2025-09-19 17:15:36
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Plasmonic Au nanoparticle-decorated Bi2Se3 nanoflowers with outstanding electrocatalytic performance for hydrogen evolution
摘要： Hydrogen production from water splitting through electrocatalytic or photoelectrochemical route shows great potential for renewable energy conversion. Herein, the plasmon-enhanced photoelectrical nanocatalysts (NCs) have been successfully developed by Au nanoparticle-decorated Bi2Se3 nanoflowers (Au@Bi2Se3 NFs) as catalysts for hydrogen evolution reaction (HER), leading to a more than 3-fold increase of current under excitation of Au localized surface plasmon resonance (LSPR) and affording a markedly decreased overpotential of 375 mV at a current density of 10 mA cm?2. The HER enhancement can be largely attributed to effective electron-charge separation and the increase of carrier density in Bi2Se3 induced by the injection of hot electrons of Au nanoparticles. Meanwhile, Bi2Se3 nanoflowers (NFs), a kind of topological insulators, possess gapless edges on boundary and show metallic character on surface, providing a path for the flow of electrons in the electrocatalytic system. This study opens up a new avenue towards the design of higher energy conversion catalytic water splitting systems with the assistance of light energy, which could increase of HER catalysis efficiency by plasmonic excitation.
关键词： Hydrogen evolution reaction,Plasmonic,Bi2Se3,Au
更新于2025-09-16 10:30:52
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Ultrahigh Stability 3D TI Bi <sub/>2</sub> Se <sub/>3</sub> /MoO <sub/>3</sub> Thin Film Heterojunction Infrared Photodetector at Optical Communication Waveband
摘要： Infrared (IR) detection at 1300–1650 nm (optical communication waveband) is of great significance due to its wide range of applications in commerce and military. Three dimensional (3D) topological insulator (TI) Bi2Se3 is considered a promising candidate toward high-performance IR applications. Nevertheless, the IR devices based on Bi2Se3 thin films are rarely reported. Here, a 3D TI Bi2Se3/MoO3 thin film heterojunction photodetector is shown that possesses ultrahigh responsivity (Ri), external quantum efficiency (EQE), and detectivity (D*) in the broadband spectrum (405–1550 nm). The highest on–off ratio of the optimized device can reach up to 5.32 × 104. Ri, D*, and the EQE can reach 1.6 × 104 A W?1, 5.79 × 1011 cm2 Hz1/2 W?1, and 4.9 × 104% (@ 405 nm), respectively. Surprisingly, the Ri can achieve 2.61 × 103 A W?1 at an optical communication wavelength (@ 1310 nm) with a fast response time (63 μs), which is two orders of magnitude faster than that of other TIs-based devices. In addition, the device demonstrates brilliant long-term (>100 days) environmental stability under environmental conditions without any protective measures. Excellent device photoelectric properties illustrate that the 3D TI/inorganic heterojunction is an appropriate way for manufacturing high-performance photodetectors in the optical communication, military, and imaging fields.
关键词： photodetectors,Bi2Se3 thin films,infrared optical communication wavebands,heterojunction structures,ultrafast response times
更新于2025-09-16 10:30:52
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Ultra-fast and high flexibility near-infrared photodetectors based on Bi2Se3 nanobelts grown via catalyst-free van der Waals epitaxy
摘要： van der Waals epitaxy (vdWe) method has recently attracted considerable interest due to its extensive application in the growth of layered structure materials. However, the growth process of vdWe is not completely understood. Here, we report the controlled growth process of Bi2Se3 nanobelts and study their photoresponse behaviour. The average length of nanobelts increases from 7 mm to 17 mm by adjusting the temperature of Bi2Se3 powder from 520 (cid:1)C to 530 (cid:1)C, however the average length becomes saturated with further increasing the source material temperature over 530 (cid:1)C. Such a change can be attributed to the competition between the process of Bi2Se3 molecule diffusion and the process of crystal formation-related chemical reaction, leading to a symmetrically studying for the growth process of catalyst-free vdWe growth of Bi2Se3 nanobelts. The photodetectors based on these Bi2Se3 nanobelts show excellent device performance in the near-infrared light range, including an ultra-fast photoresponse (trsing z 37 ms, tdecay z 62 ms), a high responsivity of 10.1 mA/W and a high detectivity of 4.63 (cid:3) 108 Jones. This high device performance could be related to the excellent carrier transport properties as Bi2Se3 nanobelt photodetectors also demonstrate a great potential for fabricating ?exible and wearable electronics by still showing stable photoresponse after bending the device for 200 times.
关键词： 2D NIR photodetectors,Catalyst-free van der Waals epitaxy,Bi2Se3 nanobelts
更新于2025-09-12 10:27:22
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Growth Habits of Bismuth Selenide (Bi2Se3) layers and nanowires over Stranski–Krastanov Indium Arsenide Quantum Dots
摘要： Bismuth selenide layers and nanowires have been grown by molecular beam epitaxy on self-assembled Stranski–Krastanov InAs quantum dots of different sizes and densities on GaAs substrates. The size and density of the InAs quantum dots were modified by changes in the growth rate and composition. The structure and growth habits of the Bi2Se3 layers were studied by high-resolution x-ray diffraction, scanning probe microscopy, energy-dispersive x-ray spectroscopy and high-resolution electron microscopy. The epitaxial growth of continuous layers of (0001) Bi2Se3 was observed over flat InAs surfaces. In contrast, the presence of InAs quantum dots induced the growth of 100 nm-long and 20 nm-wide Bi2Se3 nanowires primarily oriented along [01-1] and [0-1-1] directions. The nanowires coalesced into full layers when the growth proceeded further. Better understanding and control of the Bi2Se3 growth habits over these surfaces should lead to novel nanostructures with enhanced physical properties.
关键词： InAs quantum dots,Bi2Se3,nanowires,topological insulator,Bismuth selenide,molecular beam epitaxy
更新于2025-09-12 10:27:22
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Anharmonicity of Bi <sub/>2</sub> Se <sub/>3</sub> revealed by fs transient optical spectroscopy
摘要： We investigate the anharmonic effects in Bi2Se3 crystals using femtosecond transient optical spectroscopy at 5–280 K. The re?ectivity time series consist of exponential decay due to hot carriers and decaying oscillations due to the A1 1g phonon vibration. Vibration frequency and dephasing time of this optical phonon mode are obtained as a function of temperature, decreasing with increasing temperature; both the red shift in frequency and the increased dephasing rate induced by heating can be well described using the anharmonicity model including lattice thermal expansion and phonon-phonon coupling.
关键词： Bi2Se3,femtosecond transient optical spectroscopy,phonon dynamics,anharmonicity,thermal expansion,phonon-phonon coupling
更新于2025-09-11 14:15:04
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Visible-Light Influenced Photocatalytic Activity of Polyaniline -Bismuth Selenide Composites for the Degradation of Methyl Orange, Rhodamine B and Malachite Green dyes
摘要： Polyaniline (PANI) when composited with bismuth selenide nanoflakes (Bi2Se3 NFs), a low bandgap semiconductor, reveals enhanced photocatalytic activity for degradation of organic dyes under irradiation of visible light. The composites synthesized using Bi2Se3NFs templates with different weight percentages of PANI by in-situ chemical oxidative polymerization have been used as efficient photocatalysts for degradation of anionic dye, Methyl Orange (MO), and cationic dyes, Rhodamine B (RhB) and Malachite Green (MG). Based on radical trapping experiments, the mechanism for the photocatalytic degradation of the dyes were proposed taking into account the synergistic effect of PANI with Bi2Se3NFs. The efficient visible-light active photocatalytic property of the polymer-inorganic composites is attributed to composites’ enhanced separation of photogenerated carriers compared to its individual constituents.
关键词： Photocatalysts,PANI,Bi2Se3,Visible light,Dyes,Composites
更新于2025-09-10 09:29:36
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Interfacial reactions in In/Bi2Se3, In/Bi2Te3 and In/Bi2(Se0.2Te0.8)3 couples
摘要： Bi2(Se,Te)3 is the most commonly used N-type thermoelectric materials. The interfacial reactions in In/Bi2Se3 and In/Bi2Te3 couples at 400 (cid:1)C, 250 (cid:1)C and 200 (cid:1)C and In/Bi2(Se0.2Te0.8)3 couples at 250 (cid:1)C are systematically determined for the first time. Significant interfacial reactions are observed in all the couples. The reaction rate decreases when the reaction temperature is reduced and the reaction is fastest in the In/Bi2Te3 couple and slowest in the In/Bi2Se3 couple. After reaction for 5 minutes, the thickness of the reaction layer in the In/Bi2Te3 couple is 439 mm, 44 mm and 14 mm at 400 (cid:1)C, 250 (cid:1)C and 200 (cid:1)C, respectively. The reaction phases and reaction paths in these couples are determined. In the In/Bi2(Se0.2Te0.8)3 couple that is reacted at 250 (cid:1)C, the reaction path is liquid(In)/In4(Se,Te)3/liquid/(Bi2)m(Bi2(Se,Te)3)n/Bi2(Se0.2Te0.8)3. At 400 (cid:1)C and 250 (cid:1)C, Se and Te are the species that diffuse fastest in the reaction couples and the reaction path is primarily controlled by the speed with which Se and Te diffuse. However, the diffusion rates for Se and Te decrease significantly when the reaction temperature is reduced and at 200 (cid:1)C, Se and Te cease to be the dominating diffusion species in the couples.
关键词： Bi2(Se0.2Te0.8)3,Interfacial reactions,Indium,Bi2Te3,Bi2Se3
更新于2025-09-10 09:29:36