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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
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Formation Mechanisms of InGaAs Nanowires Produced by a Solid-Source Two-Step Chemical Vapor Deposition
摘要： The morphologies and microstructures of Au-catalyzed InGaAs nanowires (NWs) prepared by a two-step solid-source chemical vapor deposition (CVD) method were systematically investigated using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The detailed structural characterization and statistical analysis reveal that two specific morphologies are dominant in InGaAs NWs, a zigzag surface morphology and a smooth surface morphology. The zigzag morphology results from the periodic existence of twining structures, and the smooth morphology results from a lack of twining structures. HRTEM images and energy-dispersive X-ray spectroscopy (EDX) indicate that the catalyst heads have two structures, Au4In and AuIn2, which produce InGaAs NWs in a cubic phase crystalline form. The growth mechanism of the InGaAs NWs begins with Au nanoparticles melting into small spheres. In atoms are diffused into the Au spheres to form an Au-In alloy. When the concentration of In inside the alloy reaches its saturation point, the In precipitate reacts with Ga and As atoms to form InGaAs at the interface between the catalyst and substrate. Once the InGaAs compound forms, additional precipitation and reactions only occur at the interface of the InGaAs and the catalyst. These results provide a fundamental understanding of the InGaAs NW growth process which is critical to the formation of high-quality InGaAs NWs for various device applications.
关键词： HRTEM,Morphology,Formation mechanism,InGaAs nanowires,Microstructures
更新于2025-09-09 09:28:46
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Effect of Annealing on the Surface Morphology, Optical and and Structural Properties of Nanodimensional Tungsten Oxide Prepared by Coprecipitation Technique
摘要： Tungsten oxide (WO3) nanoparticles with monoclinic structure have been synthesized by using an inexpensive coprecipitation process. The obtained nanoparticles were annealed at 400°C, 500°C, 600°C, 700°C, 800°C, and 900°C for 1 h under the same physical conditions. The morphology, structure, and optical properties of the synthesized nanoparticles were studied by x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet–visible (UV–Vis) spectrophotometry, and Raman spectroscopy. The XRD results confirmed that the synthesized nanomaterial was crystalline in nature with monoclinic phase. The crystallite size varied from 14 nm to 87 nm when changing the annealing temperature. Williamson–Hall analysis was used to investigate the change in lattice strain and crystallite size. The optical performance was investigated by using UV–visible spectroscopy. The bandgap of the prepared nanomaterials varied from 2.51 eV to 3.77 eV with the annealing temperature, due to the variation of the effect of oxygen vacancies on the electronic band structure. SEM revealed formation of uniform and irregular-sized nanoparticles. HRTEM analysis revealed that the nanoparticles grew along the [002] plane with d-spacing of 0.39 nm for the material annealed at 500°C and along the [200] plane with spacing of 0.36 nm when annealed at 800°C. The crystalline nature of the synthesized nanomaterial was confirmed by uniform and clear fringes obtained in TEM micrographs. The correlation between the peak position and width of the key band at 806 cm?1 in Raman spectroscopy band is discussed. These enhancements in the properties of WO3 nanomaterial make it an efficient material for many potential applications, e.g., in photocatalysis, electro- and photochromic devices, etc.
关键词： HRTEM,XRD,SEM,UV–Vis spectroscopy,Raman spectroscopy
更新于2025-09-04 15:30:14