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VO2 microrods synthesized from V2O5 thin films
摘要： Self-assembled single crystal VO2 microrods (MRs) with a length up to 600 μm have been synthesized on Si and sapphire substrates by the annealing of V2O5 thin films. The nucleation and growth of VO2 MRs from V2O5 thin films were investigated. The morphology and microstructure evolutions of the intermediate phases during the reduction process were characterized by SEM, HRTEM, XPEEM, and Raman spectroscopy. The results have shown that the conversion of V2O5 thin films to VO2 MRs is dominated by a melting-nucleation-growth mechanism. The growth of VO2 MRs can be controlled by V2O5 melting process and a consistent feeding of V2O5 liquids to the growing VO2 MR would lead to ultra-long VO2 MRs. Further, epitaxial growth of VO2 MRs can be induced by using an r-cut sapphire substrate.
关键词： Growth mechanism,Reduction,V2O5 thin films,VO2 microrods,Epitaxial growth
更新于2025-09-23 15:23:52
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SbSI microrod based flexible photodetectors
摘要： In this paper, SbSI microrods is prepared by using a simple hydrothermal method via sulfur powder as sulfur source. The as-synthesized SbSI microrods with sulfur as sulfur powder source has better flexibility than that of SbSI with thiourea as sulfur source due to decreasing force constant between Sb and S atom. SbSI microrod based flexible photodetectors exhibit higher specific detectivity of up to 5.43×1010 Jones, fast response speed (rise time and fall time of 61 ms and 128 ms, respectively) and also show low dark current less than 50 pA. Especially, the photoresponse performance of the SbSI microrod based flexible photodetectors are almost unchanged after different bending curvatures and bending times more than 2000 times.
关键词： higher specific detectivity,fast response speed,SbSI microrods,flexible photodetector
更新于2025-09-23 15:19:57
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Facile synthesis of ZnO microrod photodetectors by solid-state reaction
摘要： In this study, ZnO microrods were directly synthesized via a single-step solid-state reaction using ZnO powders mixed with graphite without a catalyst under an air atmosphere, instead of using vacuum systems and flowing gases. The structure, growth mechanism, and electrical and optical properties of the microrods were investigated under varying growth conditions. The high-resolution transmission electron microscopy images confirmed the formation of single-crystal ZnO microrods. The photoluminescence spectra of the microrods showed green emission, suggesting the formation of non-stoichiometric ZnO microrods due to the formation of oxygen vacancies during sintering. The length and width of the ZnO microrods could be modulated by controlling the graphite content, sintering temperature, and residual time. A simple photodetector consisting of a single-crystal ZnO microrod on a SiO2-coated Si substrate was fabricated. The photodetector exhibited a linear current–voltage curve in visible light. The slope of the curve increased under ultraviolet (UV) irradiation, maintaining a linear shape of the curve. The curve reversibly returned to the initial shape in the absence of UV illumination. The UV on-off current ratio increased because of the decrease in the off-current by compensating for the oxygen vacancies through annealing in an oxygen atmosphere. Thus, in this study, we proposed a simple and efficient approach to fabricate single-crystal ZnO microrods for application in low-cost photodetectors.
关键词： oxygen vacancies,solid-state reaction,single-crystal,ZnO microrods,photodetector
更新于2025-09-19 17:13:59
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Preparation and NH3 Gas-Sensing Properties of Double-Shelled Hollow ZnTiO3 Microrods
摘要： A novel double-shelled hollow (DSH) structure of ZnTiO3 microrods was prepared by self-templating route with the assistance of poly(diallyldimethylammonium chloride) (PDDA) in an ethylene glycol (EG) solution, which was followed by calcining. Moreover, the NH3 gas-sensing properties of the DSH ZnTiO3 microrods were studied at room temperature. The morphology and composition of DSH ZnTiO3 microrods films were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The formation process of double-shelled hollow microrods was discussed in detail. The comparative gas-sensing results revealed that the DSH ZnTiO3 microrods had a higher response to NH3 gas at room temperature than those of the TiO2 solid microrods and DSH ZnTiO3 microrods did in the dark. More importantly, the DSH ZnTiO3 microrods exhibited a strong response to low concentrations of NH3 gas at room temperature.
关键词： room-temperature,NH3 gas sensor,ZnTiO3 microrods,Double-shelled hollow
更新于2025-09-16 10:30:52
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Photovoltaic Performance of Dye-Sensitized Solar Cells Containing ZnO Microrods
摘要： At an elevated temperature of 90 °C, a chemical bath deposition using an aqueous solution of Zn(NO3)2·6H2O and (CH2)6N4 resulted in the formation of both nanoflowers and microrods of ZnO on F-doped SnO2 glass with a seed layer. The nanoflowers and microrods were sensitized with dyes for application to the photoelectrodes of dye-sensitized solar cells (DSSCs). By extending the growth time of ZnO, the formation of nanoflowers was reduced and the formation of microrods favored. As the growth time was increased from 4 to 6 and then to 8 h, the open circuit voltage (Voc) values of the DSSCs were increased, whilst the short circuit current (Jsc) values varied only slightly. Changes in the dye-loading amount, dark current, and electrochemical impedance were monitored and they revealed that the increase in Voc was found to be due to a retardation of the charge recombination between photoinjected electrons and I3? ions and resulted from a reduction in the surface area of ZnO microrods. A reduced surface area decreased the dye contents adsorbed on the ZnO microrods, and thereby decreased the light harvesting efficiency (LHE). An increase in the electron collection efficiency attributed to the suppressed charge recombination counteracted the decreased LHE, resulting in comparable Jsc values regardless of the growth time.
关键词： microrods,nanoflowers,Dye-sensitized solar cell,ZnO
更新于2025-09-11 14:15:04
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Impact of activator incorporation on red emitting rods of ZnGa2O4:Cr3+ phosphor
摘要： Chromium doped zinc gallium oxide (ZnGa2O4:Cr3+) microrods were synthesized by simple solid state reaction method. The transformation on crystal structure and optical properties with molar concentration of Cr3+ were analyzed. The cubic spinel nature of ZnGa2O4:Cr3+phosphor and their crystalline nature were con?rmed from x-ray di?ractogram. The average grain size of the samples range between 24 and 29 nm, with lattice parameter values greater than that of bulk. Lattice strain produced in the lattice on doping was estimated from the Williamson–Hall plot. It increases on Cr3+ doping up to 3 mol% and then decreases. Rod like nature of zinc gallate was observed from the surface morphological analysis using SEM. X-ray photoelectron spectroscopy was used for the chemical state identi?cation of the constituent elements in the compound. The photoluminescense spectra consists of various emission lines originated from the chromium ion in the spinel lattice. The purity of red emissions were observed from chromaticity diagram with a concentration quenching initiated from the dipole–dipole interaction, with increase in dopant concentration. Band gap of the samples were estimated using Kubelka-Munk equation which exhibited red shift compared to bulk due to band tailing e?ect.
关键词： Band tailing,Microrods,Cr3+ activator,Quenching
更新于2025-09-09 09:28:46
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Simultaneous Dual-mode Emission and Tunable Multicolor in the Time Domain from Lanthanide-doped Core-shell Microcrystals
摘要： The dual-mode emission and multicolor outputs in the time domain from core-shell microcrystals are presented. The core-shell microcrystals, with NaYF4:Yb/Er as the core and NaYF4:Ce/Tb/Eu as the shell, were successfully fabricated by employing the hydrothermal method, which con?nes the activator ions into a separate region and minimizes the effect of surface quenching. The material is capable of both upconversion and downshifting emission, and their multicolor outputs in response to 980 nm near-infrared (NIR) excitation laser and 252 nm, and 395 nm ultraviolet (UV) excitation light have been investigated. Furthermore, the tunable color emissions by controlling the Tb3+-Eu3+ ratio in shells and the energy transfer of Ce3+→Tb3+→Eu3+ were discussed in details. In addition, color tuning of core-shell-structured microrods from green to red region in the time domain could be obtained by setting suitable delay time. Due to downshifting multicolor outputs (time-resolved and pump-wavelength-induced downshifting) coupled with the upconversion mode, the core-shell microrods can be potentially applied to displays and high-level security.
关键词： multicolor emission,dual-mode emission,emission spectra,time-resolved,NaYF4:Yb/Er@NaYF4:Ce/Tb/Eu microrods
更新于2025-09-04 15:30:14
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Axial p–n Junctions in GaN Microrods
摘要： GaN microrods with an axial p–n junction are grown by metal-organic vapor phase epitaxy (MOVPE). Scanning electron microscopy in combination with cathodoluminescence measurements have been performed to visualize the microrod sections consisting of n- and p-type GaN and the p–n junction. Current–voltage measurements are carried out between different microrod sections to prove the successful formation of a p–n junction. Photovoltaic and photodetecting properties have been determined by illumination of the p–n junction with a UV laser. The shorter p-type sections in axial microrods and the presence of large diameter rods suggest a growth mode change from vertical to lateral growth during p-type deposition.
关键词： microrods,cathodoluminescence,MOVPE,GaN
更新于2025-09-04 15:30:14