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ALD of ZnO:Ti: Growth Mechanism and Application as an Efficient Transparent Conductive Oxide in Silicon Nanowire Solar Cells
摘要： In the quest for replacement of indium-tin-oxide (ITO), Ti-doped zinc oxide (TZO) films have been synthesized by atomic layer deposition (ALD) and applied as n-type transparent conductive oxide (TCO). TZO thin films were obtained from titanium (IV) i-propoxide (TTIP), diethyl zinc and water, by introducing TiO2 growth cycle in a ZnO matrix. Process parameters such as the order of precursor introduction, the cycle ratio and the film thickness were optimized. The as-deposited films were analyzed for their surface morphology, elemental stoichiometry, optoelectronic properties and crystallinity, using a variety of characterization techniques. The growth mechanism was investigated for the first time by in situ quartz-crystal microbalance measurements. It evidenced different insertion modes of titanium depending on the precursor introduction, as well as the etching of Zn-Et surface groups by TTIP. Resistivity as low as 1.2 × 10-3 Ω cm and transmittance > 80% in the visible range were obtained for 72-nm thick films. Finally, the first application of ALD-TZO as TCO was reported. TZO films were successfully implemented as top electrodes in silicon nanowire solar cells. The unique properties of TZO combined with conformal coverage realized by ALD technique make it possible for the cell to show almost flat EQE response, surpassing the bell-like EQE curve seen in devices with sputtered ITO top electrode.
关键词： TCO,silicon nanowire solar cells,n-type,ZnO:Ti,Atomic Layer Deposition,QCM studies
更新于2025-09-23 15:19:57
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Novel Heteroleptic Ruthenium(II) Complexes with 2,2a?2- Bipyridines Containing a Series of Electron-Donor and Electron-Acceptor Substituents in 4,4a?2-Positions: Syntheses, Characterization, and Application as Sensitizers for ZnO Nanowire-Based Solar Cells
摘要： A novel series of complexes of the formula [Ru(4,4′-X2-bpy)2(Mebpy-CN)](PF6)2 (X = ?CH3, ?OCH3, ?N(CH3)2; Mebpy-CN = 4-methyl-2,2′-bipyridine-4′-carbonitrile) have been synthesized and characterized by spectroscopic, electrochemical, and photophysical techniques. Inclusion of the electron-withdrawing substituent ?CN at one bpy ligand and di?erent electron-donor groups ?X at the 4,4′-positions of the other two bpy ligands produce a ?ne tuning of physicochemical properties. Redox potentials, electronic absorption maxima, and emission maxima correlate well with Hammett’s σ p parameters of X. Quantum mechanical calculations are consistent with experimental data. All the complexes can be anchored through the nitrile moiety of Mebpy-CN over ZnO nanowires in dye-sensitized solar cells that exhibit an improvement of light to electrical energy conversion e?ciency as the electronic asymmetry increases in the series.
关键词： Electron-donor and Electron-acceptor substituents,Ruthenium(II) complexes,ZnO nanowire-based solar cells,Dye-sensitized solar cells,2,2′-Bipyridines
更新于2025-09-23 15:19:57
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A surface photovoltaic effect-related high-performance photodetector based on a single CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3</sub> micro/nanowire
摘要： With the decrease of materials to the nanoscale, their surface states will play a crucial role in their performance. Here, an individual CH3NH3PbI3 micro/nanowire-based photodetector can show excellent sensitivity and responsivity to light with a wide wavelength range from 200 to 850 nm. A surface state-related photovoltaic effect associated with a surface barrier can be formed due to a depletion of majority carriers (holes) in the surface space charge region. At a low operation voltage, the photodetector can exhibit a low dark current. Upon illuminating near the end connected to the positive electrode, the light-induced decrease of the surface barrier leads to enhanced conduction, showing a large photocurrent. At zero bias, additionally, the photodetector can show a relatively large photogenerated voltage and current when only the vicinity of one end is illuminated. Based on the CH3NH3PbI3 micro/nanostructure performance herein, surface photovoltaic-controlled photodetectors with superior performance will have important applications in new-generation optoelectronic devices.
关键词： CH3NH3PbI3,optoelectronic devices,photodetector,surface photovoltaic effect,micro/nanowire
更新于2025-09-23 15:19:57
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On-chip single-mode CdS nanowire laser
摘要： By integrating a free-standing cadmium sulfide (CdS) nanowire onto a silicon nitride (SiN) photonic chip, we demonstrate a highly compact on-chip single-mode CdS nanowire laser. The mode selection is realized using a Mach-Zehnder interferometer (MZI) structure. When the pumping intensity exceeds the lasing threshold of 4.9 kW/cm2, on-chip single-mode lasing at ~518.9 nm is achieved with a linewidth of 0.1 nm and a side-mode suppression ratio of up to a factor of 20 (13 dB). The output of the nanowire laser is channelled into an on-chip SiN waveguide with high efficiency (up to 58%) by evanescent coupling, and the directional coupling ratio between the two output ports can be varied from 90 to 10% by predesigning the coupling length of the SiN waveguide. Our results open new opportunities for both nanowire photonic devices and on-chip light sources and may pave the way towards a new category of hybrid nanolasers for chip-integrated applications.
关键词： Mach-Zehnder interferometer,single-mode lasing,nanowire laser,on-chip nanophotonics,silicon nitride waveguide
更新于2025-09-23 15:19:57
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Electrical control of a spin qubit in InSb nanowire quantum dots: Strongly suppressed spin relaxation in high magnetic field
摘要： In this paper we investigate the impact of gating potential and magnetic ?eld on phonon induced spin relaxation rate and the speed of the electrically driven single-qubit operations inside the InSb nanowire spin qubit. We show that a strong g factor and high magnetic ?eld strength lead to the prevailing in?uence of electron-phonon scattering due to deformation potential, considered irrelevant for materials with a weak g factor, like GaAs or Si/SiGe. In this regime we ?nd that spin relaxation between qubit states is signi?cantly suppressed due to the con?nement perpendicular to the nanowire axis. We also ?nd that maximization of the number of single-qubit operations that can be performed during the lifetime of the spin qubit requres single quantum dot gating potential.
关键词： spin qubit,spin relaxation,Rabi frequency,InSb nanowire,quantum dots
更新于2025-09-23 15:19:57
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Submicron fulla??color LED pixels for microdisplays and microa??LED main displays
摘要： We demonstrate a bottom-up approach to the construction of micro-LEDs as small as 150 nm in lateral dimension. Molecular beam epitaxy (MBE) is used to fabricate such nanostructured LEDs from InGaN, from the blue to red regions of the spectrum, providing a single material set useful for an entire RGB display.
关键词： nanowire,light-emitting diode,selective area growth,GaN,quantum dot,display
更新于2025-09-23 15:19:57
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Review on III-V Semiconductor Single Nanowire-Based Room Temperature Infrared Photodetectors
摘要： Recently, III-V semiconductor nanowires have been widely explored as promising candidates for high-performance photodetectors due to their one-dimensional morphology, direct and tunable bandgap, as well as unique optical and electrical properties. Here, the recent development of III-V semiconductor-based single nanowire photodetectors for infrared photodetection is reviewed and compared, including material synthesis, representative types (under different operation principles and novel concepts), and device performance, as well as their challenges and future perspectives.
关键词： nanowire,III-V semiconductor,infrared photodetector
更新于2025-09-23 15:19:57
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Study of nanometer-scale structures and electrostatic properties of InAs quantum dots decorating GaAs/AlAs core/shell nanowires
摘要： The configurations of core/shell nanowires (NWs) and quantum dots (QDs) decorating NWs have found great applications in forming optoelectronic devices thanks to their superior performances, and the combination of the two configurations would expect to bring more benefits. However, the nanometer-scale electrostatic properties of the QD/buffer layer/NW heterostructures are still un-revealed. In this study, the InAs QDs decorating GaAs/AlAs core/shell NWs are systemically studied both experimentally and theoretically. The layered atomic structures, chemical information, and anisotropic strain conditions are characterized by comprehensive transmission electron microscopy (TEM) techniques. Quantitative electron holography analyses show large number of electrons accumulating in the InAs QD especially at the dot apex, and charges of reversed signs and similar densities are observed to distribute at the sequential interfaces, leaving great amount of holes in the NW core. Theoretical calculations including simulated heterostructural band structures, interfacial charge transfer, and chemical bonding analysis are in good accordance with the experimental results, and prove the important role of AlAs buffer layer in adjusting the heterostructural band structure as well as forming stable InAs QDs on the NW surfaces. These results could be significant for achieving related optoelectronic devices with better stability and higher efficiency.
关键词： quantum dot,transmission electron microscopy,atomic structure,core/shell nanowire,electrostatic property
更新于2025-09-23 15:19:57
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Wafer-scale HfO<sub>2</sub> encapsulated silicon nanowire field effect transistor for efficient label-free DNA hybridization detection in dry environment
摘要： Silicon nanowire (SiNW) charge based biosensors are attractive for DNA sensing applications due to their compactness and large surface-to-volume ratio. Small feature size, low production cost, repeatability, high sensitivity and selectivity are some of the key requirements for biosensors. The most common e-beam manufacturing method employed to manufacture sub-nm SiNWs is both cost and time intensive. Therefore, we propose a highly reproducible CMOS industry grade low-cost process to fabricate SiNW based field effect transistors on 4”-wafers. The 60 nm wide SiNWs reported in this paper are fabricated using the sidewall transfer lithography process which is a self-aligned-double-patterning I-line lithography process that also facilitates encapsulation of the SiNW surface with a thin HfO2 layer on which DNA probes are grafted to finalize the biosensors. Upon DNA hybridization, SiNW devices exhibit threshold voltage shift larger than the noise introduced by the exposition to saline solutions used for the bioprocesses. More specifically, based on a statistical analysis, we demonstrate that 85% of the tested devices exhibit a positive threshold voltage shift after DNA hybridization. These promising results make way for the monolithic integration of SiNW biosensors and CMOS circuitry to realize a point of care device which can offer reliable real time electrical readout.
关键词： HfO2 passivation,silicon nanowire hybridization,silicon nanowire,DNA sensing,pattern transfer lithography,biosensor
更新于2025-09-19 17:15:36
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Determination of size dependent carrier capture in InGaN/GaN quantum nanowires by femto-second transient absorption spectroscopy: effect of optical phonon, electron-electron scattering and diffusion
摘要： Understanding the ultrafast processes corresponding to carrier capture, thermalization and relaxation is essential to design high-speed optoelectronic devices. Here, we have investigated size dependent carrier capture process in InGaN/GaN 20 nm, 50 nm nanowires and quantum well systems. Femto-second transient absorption spectroscopy reveals that the carrier capture is a two-step process. The carriers are captured in the barrier by polar optical phonon scattering. They further scatter into the active region by electron-electron and polar optical phonon scatterings. The capture is found to slow down for quantum confined structures. A significant number of carriers are found to disappear from the barrier during the diffusion process. All the experimental observations are explained in a simulation framework depicting various scattering mechanisms.
关键词： nanowire,polar optical phonon scattering,electron-electron scattering,transient absorption spectroscopy,carrier capture,electron and phonon dynamics
更新于2025-09-19 17:15:36