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Angstrom Thick ZnO Passivation Layer to Improve the Photoelectrochemical Water Splitting Performance of a TiO2 Nanowire Photoanode: The Role of Deposition Temperature
摘要： In this paper, we demonstrate that angstrom thick single atomic layer deposited (ALD) ZnO passivation can significantly improve the photoelectrochemical (PEC) activity of hydrothermally grown TiO2 NWs. It is found that this ultrathin ZnO coating can passivate the TiO2 surface defect states without hampering the carrier’s transfer dynamics. Moreover, a substantial improvement can be acquired by changing the deposition temperature of the ZnO layer (80 °C, and 250 °C) and named as 80 °C TiO2-ZnO, and 250 °C TiO2-ZnO. It was found that the deposition of this single layer in lower temperatures can lead to higher PEC activity compared to that deposited in higher ones. As a result of our PEC characterizations, it is proved that photoconversion efficiency of bare TiO2 NWs can be improved by a factor of 1.5 upon coating it with a single ZnO layer at 80 °C. Moreover, considering the fact that this layer is a passivating coating rather than a continuous layer, it also keeps the PEC stability of the design while this feature cannot be obtained in a thick shell layer case. This paper proposes a bottom up approach to control the electron transfer dynamics in a heterojunction design and it can be applied to other metal oxide combinations.
关键词： deposition temperature,atomic layer deposition,photoelectrochemical water splitting,ZnO passivation,TiO2 nanowire
更新于2025-09-23 15:21:01
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Intrinsic anion diffusivity in lead halide perovskites is facilitated by a soft lattice
摘要： Facile ionic transport in lead halide perovskites plays a critical role in device performance. Understanding the microscopic origins of high ionic conductivities has been complicated by indirect measurements and sample microstructural heterogeneities. Here, we report the direct visualization of halide anion interdiffusion in CsPbCl3–CsPbBr3 single crystalline perovskite nanowire heterojunctions using wide-field and confocal photoluminescence measurements. The combination of nanoscale imaging techniques with these single crystalline materials allows us to measure intrinsic anionic lattice diffusivities, free from complications of microscale inhomogeneity. Halide diffusivities were found to be between 10?13 and ～10?12 cm2/second at about 100 °C, which are several orders of magnitudes lower than those reported in polycrystalline thin films. Spatially resolved photoluminescence lifetimes and surface potential measurements provide evidence of the central role of halide vacancies in facilitating ionic diffusion. Vacancy formation free energies computed from molecular simulation are small due to the easily deformable perovskite lattice, accounting for the high equilibrium vacancy concentration. Furthermore, molecular simulations suggest that ionic motion is facilitated by low-frequency lattice modes, resulting in low activation barriers for vacancy-mediated transport. This work elucidates the intrinsic solid-state ion diffusion mechanisms in this class of semisoft materials and offers guidelines for engineering materials with long-term stability in functional devices.
关键词： anion diffusivity,nanoscale imaging,molecular simulation,halide perovskite nanowire,soft lattice
更新于2025-09-23 15:21:01
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Direct Electrochemical Preparation of Nanostructured Silicon Carbide and Its Nitridation Behavior
摘要： Silicon carbide was synthesized from mixtures of SiO2 and graphite by applying the concept of the FFC-Cambridge process and several fundamental aspects of the synthesis route were investigated. Porous disks composed of powders of SiO2 and graphite in molar ratios of 1:0.5, 1:1 and 1:1.5 were prepared by sintering in inert atmosphere and subjected to electro-deoxidation in molten CaCl2 at 1173 K under a range of experimental conditions. Disks of molar ratio 1:1.5, reduced at an applied voltage of 2.8 V for a duration of 6 h, yielded exclusively phase-pure SiC of nanowire morphology as the reaction product, while the other precursor compositions provided significant amounts of calcium silicides. Voltages lower than 2.8 V gave mixtures of SiC with elemental Si and graphite, and voltages higher than that gave CaSi alone. Shorter electro-deoxidation times led to incomplete reduction and allowed for the identification of CaSiO3 as a transient phase. Based on the experimental results a multipath reaction mechanism is proposed, consisting of the electrochemical reduction of SiO2 and CaSiO3 to Si and the subsequent in-situ carbonization of the Si formed to SiC. The effect of N2 at high temperature on the electrochemically synthesized SiC was investigated and the formation of nanowire Si2N2O was observed. Overall, the process presented is a facile single-step and low-temperature method for the synthesis of SiC with possible commercial prospects.
关键词： electro-deoxidation,Silicon carbide,Si2N2O,molten CaCl2,FFC-Cambridge process,nanowire morphology
更新于2025-09-23 15:21:01
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Cd(OH)2@ZnO nanowires thin-film transistor and UV photodetector with a floating ionic gate tuned by a triboelectric nanogenerator
摘要： The adsorbed ions on the surface of nanowires thin-film, such as O2-, are acted as a floating gate, modulating significantly the thin-film’s electronic and optoelectronic properties. However, due to the lack of tuning means for surface ions, the floating ionic gate has not been applied in developing electronic and optoelectronic nanodevices. Here, based on the gas discharge induced by a triboelectric nanogenerator (TENG), the tuning of surface ions on Cd(OH)2@ZnO nanowires thin-film is achieved, and the thin-film transistor (TFT) and thin-film photodetector (TFP) have been fabricated by using the surface ions as a floating ionic gate. In the TFT with a floating ionic gate, the current can be tuned step-by-step as the operation cycles of TENG is controlled, and the maximum on-off ratio of current reaches 4.0×105. In the UV light TFP with a floating ionic gate, the on-off ratio and recovery time constant of photocurrent reach 2.7×107 and 0.53 s, achieving a simultaneous enhancement of sensitivity and recovery speed by a factor of 1350 and 946 times, respectively. O2- is identified as the surface ions on the nanowire thin-film, and the tuning mechanism has been discussed. Because of the low cost and easy operation of the TENG, the floating ionic gate technology based on TENG provides a promising strategy for developing novel electronic and optoelectronic nanodevices with enhanced performances by constructing a device system.
关键词： TENG,UV photodetector,ZnO nanowire film,air discharge
更新于2025-09-23 15:21:01
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Vectorial control of the spin-orbit interaction in suspended InAs nanowires
摘要： Semiconductor nanowires featuring strong spin-orbit interactions (SOI), represent a promising platform for a broad range of novel technologies, such as spintronic applications or topological quantum computation. However, experimental studies into the nature and the orientation of the SOI vector in these wires remain limited despite being of upmost importance. Typical devices feature the nanowires placed on top of a substrate which modifies the SOI vector and spoils the intrinsic symmetries of the system. In this work, we report experimental results on suspended InAs nanowires, in which the wire symmetries are fully preserved and clearly visible in transport measurements. Using a vectorial magnet, the non-trivial evolution of weak anti-localization (WAL) is tracked through all 3D space, and both the spin-orbit length lSO and coherence length l? are determined as a function of the magnetic field magnitude and direction. Studying the angular maps of the WAL signal, we demonstrate that the average SOI within the nanowire is isotropic and that our findings are consistent with a semiclassical quasi-1D model of WAL adapted to include the geometrical constraints of the nanostructure. Moreover, by acting on properly designed side gates, we apply an external electric field introducing an additional vectorial Rashba spin-orbit component whose strength can be controlled by external means. These results give important hints on the intrinsic nature of suspended nanowire and can be interesting for the field of spintronics as well as for the manipulation of Majorana bound states in devices based on hybrid semiconductors.
关键词： weak anti-localization,spin-orbit interaction,Rashba effect,indium arsenide,nanowire
更新于2025-09-23 15:21:01
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A Predictive Model for the Electrical Transport Within Nanowire Networks
摘要： Thin networks of high aspect ratio conductive nanowires can combine high electrical conductivity with excellent optical transparency, which has led to a widespread use of nanowires in transparent electrodes, transistors, sensors, and ?exible and stretchable conductors. Although the material and application aspects of conductive nanowire ?lms have been thoroughly explored, there is still no model which can relate fundamental physical quantities, like wire resistance, contact resistance and nanowire density, to the sheet resistance of the ?lm. Here we derive an analytical model for the electrical conduction within nanowire networks based on an analysis of the parallel resistor network. The model captures the transport characteristics and ?ts a wide range of experimental data, allowing for the determination of physical parameters and performance limiting factors, in sharp contrast to the commonly employed percolation theory. The model thus constitutes a useful tool with predictive power for the evaluation and optimization of nanowire networks in various applications.
关键词： nanowires,electrical transport,model,percolation,carbon nanotubes,nanowire network,silver nanowires
更新于2025-09-23 15:21:01
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Suppression of Ag migration by low-temperature sol-gel zinc oxide in the Ag nanowires transparent electrode-based flexible perovskite solar cells
摘要： Silver nanowires (Ag NWs) network is an excellent candidate as flexible transparent electrode applying in flexible perovskite solar cells, owing to their excellent electrical and optical properties. However, several problems including large surface roughness, chemical reaction between Ag and perovskite precursor, and migration of Ag limited the application in high performance perovskite solar cells. Aiming to solve these problems, the composite electrode combining the spray coated Ag nanowires and the low-temperature sol-gel zinc oxide was developed in this work. The optimized concentration and annealing temperature of sol-gel ZnO were 0.45 M and 150°C. The introduction of zinc oxide with suitable concentration caused slight impact on the transmittance and sheet resistant of transparent composite electrode, and promoted mechanical and chemical stability in air relative to the pristine Ag NWs electrode. The use of the composite flexible electrode could decrease the surface roughness of the Ag NWs electrode, passivate the reaction of perovskite and silver electrode, and prevent the migration of Ag. As a consequence, the performance of the flexible device significantly improved from 9.51% to 13.12%. Under the AM 1.5G constant illumination, the optimization device has a remarkably improved stability than pristine device. This study demonstrates that spray Ag NWs as bottom electrode is suitable for flexible perovskite solar cells. Meanwhile, it’s an effective method using sol-gel ZnO to construct composite electrode to promote the device performance and stability.
关键词： Ag nanowire electrode,Ag migration,Flexible perovskite solar cells,Sol-gel ZnO,Bending resistance
更新于2025-09-23 15:21:01
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A Si-based InP/InGaAs nanowire array photodetector operating at telecommunication wavelength
摘要： A Si-based vertical nanowire heterostructure array photodetector is designed and studied by a coupled three-dimensional optoelectronic simulation. Each nanowire is composed of an InP/In0.53Ga0.47As/InP axial p-i-n junction, which is designed to operate at telecommunication wavelengths. The results show that the absorption of the nanowire array strongly depends on the D/P ratio and nanowire diameter. By tuning the D/P ratio and diameter simultaneously, the peak absorption wavelength could be fixed at 1550 nm. Due to the light-trapping and light-concentrating properties, the nanowire array photodetector exhibits a remarkable responsivity beyond 0.8 A/W, several times higher than its thin film counterpart with the equivalent thickness. This work suggests that the III-V nanowire array is promising for high-performance Si-based photodetectors applied in optical telecommunication systems.
关键词： Nanowire array,Light-trapping,Optical communication,Si-based,InGaAs/InP
更新于2025-09-23 15:21:01
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Structural properties of silicon–germanium and germanium–silicon core–shell nanowires
摘要： Core–shell nanowires made of Si and Ge can be grown experimentally with excellent control for different sizes of both core and shell. We have studied the structural properties of Si/Ge and Ge/Si core–shell nanowires aligned along the [1 1 0] direction, with diameters up to 10.2 nm and varying core to shell ratios, using linear scaling density functional theory. We show that Vegard’s law, which is often used to predict the axial lattice constant, can lead to an error of up to 1%, underlining the need for a detailed ab initio atomistic treatment of the nanowire structure. We analyse the character of the intrinsic strain distribution and show that, regardless of the composition or bond direction, the Si core or shell always expands. In contrast, the strain patterns in the Ge shell or core are highly sensitive to the location, composition and bond direction. The highest strains are found at heterojunction interfaces and the surfaces of the nanowires. This detailed understanding of the atomistic structure and strain paves the way for studies of the electronic properties of core–shell nanowires and investigations of doping and structure defects.
关键词： Vegard’s law,nanowire,linear scaling density functional theory,core–shell
更新于2025-09-23 15:21:01
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Efficient metallic nanowire welding using eddy current method
摘要： In this study, M-NWs such as silver nanowires (AgNWs) and copper nanowires (CuNWs) were welded only at junction resistively by a novel method using indirect Eddy current through the inductive power transfer. By applying the inductive power of 45 kHz alternating current (AC) power indirectly for 6 s to the M-NW network deposited on polymer substrates, the decrease of sheet resistance up to ~67.9 % for AgNW and ~49.9 % for CuNWs could be obtained without changing the optical transmittance. For AgNWs, after the welding the decrease of surface roughness from 44.5 nm to 26.3 nm which is similar to a height of single layer AgNW (22.2 nm) for a bilayer junction could be also observed. For AgNWs coated on transparent flexible substrate, after the cyclic bending of 10,000 times, no change of resistance (ΔR/R0) of the AgNWs after the welding was observed and the welded AgNWs were not easily peeled off from the substrate. It is believed that this novel welding method can be applied not only to all kinds of metal nanowires on various flexible low-temperature polymer substrates but also to large area at a short time and at low-cost.
关键词： nanowelding,inductive coil system,Eddy current,nanowire
更新于2025-09-23 15:21:01