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Crystallographically oriented porous ZnO nanostructures with visible-blind photoresponse: controlling the growth and optical properties
摘要： We have grown catalyst-free crystallographically oriented porous ZnO nanostructures by pulsed laser deposition (PLD) method. The deposition was performed in two stages for each sample. In the first stage, self-seeding of ZnO was performed on the quartz substrate, and the angle of deposition (seeding-angle) was varied. Thus, the growth of seeds is different here. In the second stage, the deposition was performed at a glancing angle (at 85?) for the fixed duration of time to grow the nanostructures. These PLD-grown nanostructures acquire highly oriented wurtzite structure. We find that the seeding-angle during the first stage is the determining deposition parameter which influences the growth and other properties of these nanostructures in a controllable manner. The variation in seeding-angle systematically tunes the crystallographic orientation and porosity, which in turn influences the visible-blindness and ultraviolet (UV) photoresponse of these nanonetworks. Here we report the growth of completely defect-free crystallographically oriented nanostructures with necessary porosity for application in visible-blind UV photodetection.
关键词： Crystalline ZnO,catalyst-free ZnO,glancing angle deposition (GLAD),seeding,pulsed laser deposition (PLD),nanostructures
更新于2025-11-21 11:03:13
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A novel Ag nanoparticles/TiO2 nanowires-based photodetector and glucose concentration detection
摘要： A unique vapour transport cum glancing angle deposition (VT-GLAD) technique was employed to fabricate titanium dioxide (TiO2) nanowires (NWs). The NWs were grown and assembled to form the clusters. Both brookite (412) and rutile (002) phase for TiO2 was obtained from X-ray diffraction (XRD). The d spacing of ~ 1.37 ? was calculated from the transmission electron microscopy (TEM) of TiO2 NWs, which corresponds to (002) crystal plane. The silver (Ag) nanoparticles (NPs) on TiO2 NWs were grown using thermal evaporation cum GLAD technique. The presence of Ag NPs on the TiO2 NWs enhanced the photoconduction as compared to bare TiO2 NWs device. The maximum photosensitivity of the Ag NPs/TiO2 NWs based device was recorded ~ 1.6 times compared to the bare TiO2 NWs based device at ? 2.5 V. The Ag NPs containing device was highly UV sensitive and maximum responsivity for the device was calculated to be ~ 2.3 A/W at 370 nm. The device also possessed high responsivity rejection (RR) ratio of ~ 6.5 between UV (370 nm) and visible (450 nm) light. The Ag NPs decorated TiO2 NWs based detector also showed response to white light. The different concentration of glucose into deionised (DI) water-based solution was detected precisely under white light illumination. The normalised (light/dark) detector current/glucose concentration value was decreased from ~ 0.19 to ~ 0.05 at ? 2.5 V, with an increase in glucose concentration into the solution from 40 mg/dl to 200 mg/dl.
关键词： photodetector,Ag nanoparticles,TiO2 nanowires,VT-GLAD technique,glucose concentration detection
更新于2025-11-21 11:01:37
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Plasmon-induced Ag decorated CeO <sub/>2</sub> nanorod array for photodetector application
摘要： In this work, glancing angle deposition (GLAD) has been used to grow Ag decorated CeO2 nanorod (NR) array on n-type Si substrate. The length of the NRs obtained was ～235 nm and the size of the Ag NPs varied from 13 to 41 nm. The polycrystalline and crystalline nature of CeO2 and Ag respectively was revealed via selected area electron diffraction (SAED) analysis as well as x-ray diffraction (XRD) pattern. Optical absorption measurement depicts a distinct broad peak around 413 nm that is ascribed to the localized surface plasmon resonance (LSPR) effect of Ag NPs. The Ag decorated CeO2 NR device exhibited a turn on voltage at ～3.2 V under dark, which then reduced to ～1.3 V under 35 min illumination along with the increase in device current from 2.8 to 24.5 μA cm?2 (4 V) on continuous exposure to light. Under white light illumination, a responsivity of 4.51 A W?1 was obtained at 370 nm along with the detectivity and noise equivalent power (NEP) values of 4.15×1012 jones and 0.01 pW respectively. Additionally, a fast response characteristic with rise and fall times of 74 ms and 42 ms respectively was demonstrated. Thus, these findings manifest the underlying LSPR mechanism at work in Ag/CeO2 heterojunction and reveal its high potential in UV photodetector application.
关键词： GLAD,surface plasmon,nanorod,silver,nanoparticle,cerium oxide
更新于2025-09-23 15:19:57
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Nitric oxide sensors using nanospiral ZnO thin film deposited by GLAD for application to exhaled human breath
摘要： ZnO is a promising gas sensing material for its excellent gas sensing response characteristics and long-term stability. Moreover, the improvement in the sensitivity and response speed of ZnO gas sensors can be achieved by the nanostructure fabrication. This paper proposes a facile method to deposit ZnO nanospirals using glancing angle deposition (GLAD) for application in nitric oxide (NO) sensors. ZnO nanospirals with porous characteristics have larger relative surface area and more active surfaces, compared with dense ZnO thin film. A sensor using nanospiral ZnO film shows a response factor of 16.9 to 100 ppb NO at 150 °C in 40% RH, which is 3 times larger than that of the sensor using dense ZnO film. Such a ZnO nanospiral sensor system can detect NO as low as 10 ppb which is below the NO concentration (>30 ppb) in exhaled breath of patients with asthma. The effects of working temperature and humidity on the sensor performance were investigated systematically in this work. Moreover, the sensor response showed a good selectivity to NO and high stability as the time increased up to 24 days. NO gas sensing mechanism was discussed in detail and nanospiral ZnO film sensors are promisingly applicable for exhaled human breath application compared with some other NO sensors.
关键词： exhaled breath,nitric oxide,GLAD,nanospiral,gas sensor,ZnO
更新于2025-09-23 15:19:57
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Synthesis of Anatase (Core)/Rutile (Shell) Nanostructured TiO <sub/>2</sub> Thin Films by Magnetron Sputtering Methods for Dye-Sensitized Solar Cell Applications
摘要： Currently, anatase/rutile core/shell structures are accepted as highly efficient building blocks for TiO2-based catalysts or photo-electrodes used in dye-sensitized solar cells (DSSCs). It is understood that a thin layer of rutile covering the core anatase pillar would improve the performance of DSSCs by retarding the charge recombination at the semiconductor/sensitizer/electrolyte interfaces. In this work, we report on the synthesis of core/shell nanostructured TiO2 thin films using reactive magnetron sputtering at a glancing angle with different power applying modes: well-separated pillars of pure anatase were synthesized using the DC mode, and then, high-pulse peak power was applied to the Ti target (high power impulse magnetron sputtering – HiPIMS) resulting in the covering of the anatase columns with a thin layer of rutile. The latter technique is well-known to increase the energy load during the growth of the film which is a key parameter to successfully obtain the TiO2 phase normally only achieved at high temperature, i.e. rutile. The peak current, the frequency and the pulse width were optimized in order to obtain the desired crystalline structure and thickness of the rutile top layer. Scanning Electron Microscopy (SEM) cross-section views of the synthesized films clearly show that the pillar-like structures are not affected by the energetic species striking the surface during the HiPIMS process. Grazing Incidence X-Ray Diffraction (GIXRD) suggests the presence of both anatase and rutile phases in the films. Further characterization of the anatase/rutile core/shell interface by electron transmission techniques such as Transmission Electron Microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS) mapping confirm the hypothesis and reveal that the anatase pillars are partly covered by a rutile crust.
关键词： EELS,Dye-Sensitized Solar Cells,TEM,TiO2,GLAD,Reactive Magnetron Sputtering,core/shell nanostructures,HiPIMS
更新于2025-09-12 10:27:22
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Tailoring of highly porous SnO2 and SnO2-Pd thin films
摘要： Tin oxide is a material that attracts attention due to varieties of technological applications. The main parameters that influence its properties are morphology, crystalline structure and stoichiometry. To influence these parameters researchers try to develop nanostructured thin films that would conform technological application. Here, we report the preparation and characterization of highly porous SnO2 and Pd doped SnO2 thin films. The films were deposited in form of nanorods with controllable geometry. Such morphology was achieved by utilizing glancing angle deposition (GLAD) with assisted magnetron sputtering. This arrangement allowed preparation of slanted pillars, zig-zag structure, vertically standing posts, spiral posts and “bush”-like structures. We calculated that slanted pillars possess highest surface area among the films listed. Then, sets of slanted pillars were deposited and studied in more details. The influence of substrate annealing during the film deposition and Pd doping on the morphology, crystalline structure and stoichiometry of the films are discussed. Characterizations of the tin oxide films were performed by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and synchrotron radiation photoelectron spectroscopy (SRPES). GLAD with assisted magnetron sputtering allowed us to deposit broad range of SnO2 nanostructures while annealing of the substrate during deposition affects the films crystallinity. Also, we find that doping of the SnO2 films with Pd leads to alloy phase formation. These findings can be applied in variety of applications including gas sensing, catalysis, optics and electronics.
关键词： XPS,SRPES,SnO2,tin oxide,glancing angle deposition,TEM,HRTEM,GLAD,highly porous
更新于2025-09-10 09:29:36