The optical absorption spectra and structural properties of samples series consisting of AZO oxide films with an intermediate layer of silver nanoparticles with different sol compounds were investigated. TEM analysis of the obtained coatings showed that the nanoparticles in the AZO film form an ordered structure, and the distance between them depends on the sol composition and the film annealing temperature. Optical measurements showed that a position of the nanoparticle plasmon peak in AZO also depends on them.
We fabricate the samples with two layers of silver nanoparticles embedded in ZnO film exploring sol–gel method by varying the annealing temperatures. The structural properties of the samples are determined by transmission electron microscopy. The effect of the annealing temperature on the nanoparticles plasmon absorption spectra is studied. Annealing at 570 °C results in a shift of the plasmon absorption maximum from 580 nm to 620 nm, due to an increase in the nanoparticles average size from 63 nm to 74 nm. Increasing the annealing temperature to 650 °C results in a shift of plasmon absorption maximum back to 580 nm due to a decrease in the nanoparticles size to 61 nm. Before annealing, the silver nanoparticles of the upper layer locate on top of the nanoparticles of the bottom layer, however, in the plane of the layers, they are arranged randomly at a distance of 30 to 150 nm from each other. As a result of the annealing, the system tended to be ordered, as a result, the nanoparticles in the layers become to be distributed equidistant at 40–70 nm between them; the nanoparticles of the upper layer tend being located between the nanoparticles of the bottom layer.
This paper presents the study of oxide film heterojunction made of CuAlCrO2 and ZnO:Al (AZO) deposited on fused quartz by sol-gel spin coating. Transmission electronmicroscopy (TEM) analysis has showed that the solvent, which was used to prepare the AZO sol, affects the thickness and planarity of the applied layers and the grain size of the polycrystalline film. The formation of a fine-grained structure of AZO films (grain size is up to 12 nm) leads to the formation of a smoother p-CuAlCrO2 / n-AZO heterojunction. X-ray diffraction (XRD) analysis and TEM have revealed that the heterojunction was formed by AZO polycrystals, which orient axes [101] and [100] against the [101] and [006] directions in CuAlCrO2 polycrystals. The optical transmission of the heterojunction in the visible range reached 70 %. The current -voltage (I-V) characteristics of p-CuAlCrO2 / n-AZO corresponds to a diode one in the range from 4 up to 4 V. For the large values of the reverse bias, an increase in the leakage current is observed, which is associated with tunneling breakdown of heterojunction. The ideality factor of fabricated p-CuAlCrO2 / n-AZO heterojunction is more than 2, which indicates the mechanisms of conductivity by defect-levels. In additional, it has been observed the response of the current-voltage characteristics to the green illumination (532 nm) of the diode that is associated with indirect band-gap absorption in CuAlCrO2. The impact of the white LED illumination had no effect on the current-voltage characteristics of the diode.
The paper presents the results of the optical and structural properties studies of samples consisting of ZnO:Al (AZO) oxide films with an intermediate silver nanoparticles layer. Obtaining samples were carried out by the method of sol-gel technology using different types of composition, and the conditions for drying and final annealing of the samples were varied. The study of the samples optical properties consisted of the optical absorption spectra measurements, and their structural properties were determined by X-ray diffraction and small-angle X-ray scattering. Comparison of data obtained from measurements of optical and structural properties of samples confirmed the results obtained from modeling in the Comsol Multiphysics software. X-ray diffraction demonstrated that the AZO films have a polycrystalline structure and are highly textured in the [002] direction. Zinc oxide grains are 10-15 nm. Silver nanoparticles are the comparable with AZO grains and have dimensions of several tens of nanometers. An increase in the annealing temperature of the films leads to a redistribution of silver nanoparticles in the AZO film, the distance between the particles increases. Consequently, the effect of the plasmon eigenmodes of the nanoparticles prevails over the effect of the system of particles oscillations interacting with each other. The analysis of the coatings obtained by the method of small-angle X-ray scattering showed that nanoparticles in the AZO film form an ordered structure.
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