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Laser-Tuned Large Photo Hall Effect in p-Type Silicon Based on Surface States
摘要： The photo Hall e?ect (PHE) has attracted much attention for a long time due to its broader application in photosensitive semiconductor devices. In this paper, we show a PHE observed in p-type silicon induced by pointolite irradiation, which di?ers from the conventional PHE caused by a surface light source. The Hall voltage is improved by 63 times when a laser is applied at the edge of the sample, and it presents good position-sensitive properties when the laser spot moves along the middle line of the sample. An ultra-broadband spectral responsivity is observed from 405 to 980 nm at 150?300 K. The experimental result shows that the laser-induced photo Hall voltage is not the simple superposition of photo current and dark current. Interestingly, this PHE can be greatly deteriorated when the surface state is destroyed and partially replaced by a Schottky barrier via covering with a thin Ag nano?lm. We attribute this phenomenon to the surface band bending caused by charged surface states. Compared with the traditional PHE, this laser-induced, position-sensitive, large-tuned-range e?ect based on surface states provides a di?erent approach to reveal the transmission properties of local unevenly distributed non-balanced carriers and can be used to design light-sensitive Hall devices.
关键词： photo Hall e?ect,surface states,recombination rate,magnetic ?eld,Schottky barrier
更新于2025-09-19 17:13:59
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Interface engineering on ZnO/Au based Schottky junction for enhanced photoresponse of UV detector with TiO2 inserting layer
摘要： Metal-oxide semiconductor ZnO shows enormous potential in the field of photoelectric detection. However, the adsorption of H2O/O2 on its surface unavoidably results in degradation in the photo-response. Herein, AueTiO2eZnO (ATZ) ultraviolet (UV) photodetectors were designed to benefit the photosensing performance by weaken the surface state effect through tuning the Schottky junction interface with TiO2 insertion layer. As expect, 97% enhancement of IPh response together with three orders of magnitude decrease of dark current was triggered. This enhancement is owing to the efficiently separation and extraction of photoexcites under the effect of the stronger and expanding built-in field, which is a result of reduction of space charge density in barrier region induced by inhibiting H2O/O2 adsorption at the ZnO/Au interface. These findings here provide a promising method to boost performances of optoelectronic devices by interface engineering and could be extended to other semiconductor devices.
关键词： Zinc nanowires,Interface engineering,Surface states,Photodetector
更新于2025-09-19 17:13:59
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Surface Nonlinear Optics on Centrosymmetric Dirac Nodal‐Line Semimetal ZrSiS
摘要： Gapless surface states (SSs) are features of topological semimetals and are extensively observed. Nowadays, the emerging question is whether the SSs possess exotic and applicable properties. Here, associated with the symmetrical selection rule for nonlinear optical materials, the surface nonlinear optics on a centrosymmetric Dirac nodal-line semimetal ZrSiS crystal is studied and it is found that the SSs bring record nonlinear susceptibilities. The unprecedented conversion efficiencies for second and third harmonic generations are 0.11‰ and 0.43‰, respectively, more than ten orders of magnitude larger than the typical surface second harmonic generation. This work discovers a new route toward studying the SSs for applications in nonlinear photonics.
关键词： density functional theory calculations,ZrSiS,surface states,nonlinear optics,symmetry breaking
更新于2025-09-11 14:15:04
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Proximity-induced supercurrent through topological insulator based nanowires for quantum computation studies
摘要： Proximity-induced superconducting energy gap in the surface states of topological insulators has been predicted to host the much wanted Majorana fermions for fault-tolerant quantum computation. Recent theoretically proposed architectures for topological quantum computation via Majoranas are based on large networks of Kitaev’s one-dimensional quantum wires, which pose a huge experimental challenge in terms of scalability of the current single nanowire based devices. Here, we address this problem by realizing robust superconductivity in junctions of fabricated topological insulator (Bi2Se3) nanowires proximity-coupled to conventional s-wave superconducting (W) electrodes. Milling technique possesses great potential in fabrication of any desired shapes and structures at nanoscale level, and therefore can be effectively utilized to scale-up the existing single nanowire based design into nanowire based network architectures. We demonstrate the dominant role of ballistic topological surface states in propagating the long-range proximity induced superconducting order with high IcRN product in long Bi2Se3 junctions. Large upper critical magnetic fields exceeding the Chandrasekhar-Clogston limit suggests the existence of robust superconducting order with spin-triplet cooper pairing. An unconventional inverse dependence of IcRN product on the width of the nanowire junction was also observed.
关键词： Topological insulators,Quantum computation,Nanowires,Majorana fermions,Ballistic topological surface states,Proximity-induced superconductivity,Spin-triplet cooper pairing
更新于2025-09-11 14:15:04
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Field Effect in PbSnTe:In Films with Low Conductivity in the Mode of Injection from Contacts and Space-Charge Limitation of the Current
摘要： At T = 4.2 K, a strong change (up to 4 times) in the space-charge-limited current (SCLC) is observed for the first time at samples based on semi-insulating PbSnTe:In films grown by molecular-beam epitaxy on BaF2(111) substrates. The obtained results agree with experiments on the effect of treatment of the surface of PbSnTe:In films on the space-charge-limited current with a variation in the current to 103 times or more. At a qualitative level, the model is considered which assumes the substantial contribution of localized surface states to space charge formed in the mode of space-charge-limited current due to the injection of charge carriers from contacts.
关键词： field effect,surface states,molecular-beam epitaxy,space-charge-limited current,PbSnTe:In films
更新于2025-09-10 09:29:36
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Role of Surface States in Photocatalytic Oxygen Evolution with CuWO <sub/>4</sub> Particles
摘要： CuWO4 is a medium bandgap (2.3 eV) n-type semiconductor capable of photoelectrochemical water oxidation under applied electrical bias. Here, we show for the ?rst time that suspended microcrystals CuWO4 evolve oxygen photocatalytically under visible illumination from solutions of 0.05 M AgNO3 (10.8 μmol/hour; AQE of 0.56% at 400 nm) and 0.0002 M FeCl3 (1.5 μmol/hour). No oxygen is detected with 0.002 M [Fe(CN)6]3? as sacri?cial agent. The activity dependence on the redox potential of the acceptors is due to the presence of Cu2+ based electron trap states in CuWO4. According to surface photovoltage spectroscopy and electrochemistry, these states are located on the particle surface, 1.8 eV above the valence band edge of the material. Controlling the chemistry of these states will be key to uses of CuWO4 particles in tandem catalysts for overall water splitting.
关键词： water splitting,CuWO4,sacrificial electron acceptors,photocatalytic oxygen evolution,surface states
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Kiev (2018.4.24-2018.4.26)] 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - ITO-Nano-Titania Gas Sensors at Adsorption of Ethanol, Acetone and Water Molecules
摘要： The measurements capacitance-voltage characteristics and capacitance kinetics were applied for investigation of physical principle of sensor response in the ITO – nanostructured titanium dioxide heterojunction. The studies were fulfilled for ethanol, acetone and water vapor under various frequencies of probing signal. It was shown that processes of surface states recharging are making the most significant contribution to the total capacitance of the studied heterojunction and playing a major role in forming of sensor response to the molecules of the used analytes.
关键词： titanium dioxide,surface states,adsorption,capacitance-voltage characteristics,capacitance kinetics,gas sensor,electronic traps,hysteresis
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Group theoretical route to weakly and strongly protected surface states in 2D and 3D photonic crystals
摘要： Topologically protected surface states in photonic systems, with unique properties such as unidirectional propagation and light con?nement insensitive to thermal or fabrication imperfections, have attracted immense attention over the past ten years. We introduce the notion of weak protection where a topological invariant predicts the existence of surface states in the photonic bulk gap, and strong protection which instead corresponds to the number of glueing points of a surface band with the bulk edges. While strong protection is desired for many key applications such as topologically protected loss-free cavities to boost non-linear interactions, it requires optical reciprocity breaking in two dimensions. We here provide a group theoretical recipe to design weakly protected states on purely dielectric metasurfaces, and genuinely strongly protected states in fully connected 3D photonic crystals. Both design principles can be readily realized by current direct manufacturing techniques, such as electron beam lithography and direct laser writing, respectively.
关键词： topologically protected surface states,strong protection,photonic crystals,group theory,weak protection
更新于2025-09-09 09:28:46
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Topological states on uneven (Pb,Sn)Se (001) surfaces
摘要： The impact of surface morphology on the electronic structure of topological crystalline insulators is studied theoretically. As an example, the structure of topologically protected electronic states on a (001) (Pb,Sn)Se surface with terraces of atomic height is modeled. Within the envelope function model it is shown that valley mixing, the phenomenon responsible for the peculiar “double Dirac cone” shape of the surface state dispersion, depends crucially on the structure of the surface. By varying the width and the number of atomic layers in the terraces, a comprehensive explanation of recent experimental ?ndings, i.e., the emergence of one-dimensional states bound to odd-height atomic step edges [P. Sessi et al., Science 354, 1269 (2016)] as well as the collapse of “double Dirac cone” structure on a rough surface [C. Polley et al., ACS Nano 12, 617 (2018)], is achieved. This approach allows us also to determine topological indices characterizing terraces and their interfaces. In the (001) surface of (Pb,Sn)Se the adjacent terraces turn out to be described by different values of the winding number topological invariant.
关键词： surface states,double Dirac cone,valley mixing,topological crystalline insulators,winding number topological invariant
更新于2025-09-09 09:28:46
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Nanowire-Based Josephson Junctions
摘要： The combination of superconductivity and surface states in Dirac semimetal can produce a 4π-periodic supercurrent in a Josephson junction configuration, which can be revealed by the missing of odd Shapiro steps (especially the n ? 1 step). However, the suppression of the n ? 1 step is also anticipated in the high-power oscillatory regime of the ordinary 2π-periodic Josephson effect, which is irrelevant to the 4π-periodic supercurrent. Here, in order to identify the origin of the suppressed n ? 1 step, we perform the measurements of radio frequency irradiation on Nb–Dirac semimetal Cd3As2 nanowire–Nb junctions with continuous power dependence at various frequencies. Besides the n ? 1 step suppression, we uncover a residual supercurrent of first node at the n ? 0 step, which provides a direct and predominant signature of the 4π-periodic supercurrent. Furthermore, by tuning the gate voltage, we can modulate the surface and bulk state contribution and the visibility of the n ? 1 step. Our results provide deep insights to explore the topological superconductivity in Dirac semimetals.
关键词： surface states,Cd3As2 nanowire,topological superconductivity,4π-periodic supercurrent,Josephson junctions
更新于2025-09-09 09:28:46