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Abstract:SnO 2 nanowires and nanobelts have been grown by the thermal evaporation of Sn powders. The growth of nanowires and nanobelts has been investigated at different temperatures (750-1000°C). The field emission scanning electron microscopic and transmission electron microscopic studies revealed the growth of nanowires and nano-belts at different growth temperatures. The growth mechanisms of the formation of the nanostructures have also been discussed. X-ray diffraction patterns showed that the nanowires and nanobe… Show more
“…IR spectra presented in Fig. 6 correspond well with the results published in the literature, especially since the 563 cm −1 band present in the 1D SnO 2 nanostructure in the current study was also reported to exist in 1D structures by others [23]. The presence of this extra absorption band in the 560–570-cm −1 region is known as a characteristic feature of 1D SnO 2 structures, but the nature of their presence still requires clarifications.Fig.…”
Section: Resultssupporting
confidence: 90%
“…There are many papers recently published that study either 0D or 1D nanostructured SnO 2 [ 15 , 16 , 23 , 24 ]. However, the direct comparison of performance of these structurally very different materials is lacking.…”
Zero- and 1D (one-dimensional) tin (IV) oxide nanostructures have been synthesized by thermal evaporation method, and a comparison of their morphology, crystal structure, sorption properties, specific surface area, as well as electrical characteristics has been performed. Synthesized SnO2 nanomaterials were studied by X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM), N2 sorption/desorption technique, IR spectroscopy and, in addition, their current-voltage characteristics have also been measured. The single crystalline structures were obtained both in case of 0D (zero-dimensional) SnO2 powders and in case of 0D nanofibers, as confirmed by electron diffraction of TEM. It was found that SnO2 synthesis parameters significantly affect materials’ properties by contributing to the difference in morphology, texture formation, changes in IR spectra of 1D structure as compared to 0D powders, increases in the specific surface area of nanofibers, and the alteration of current-voltage characteristics 0D and 1D SnO2 nanostructures. It was established that gas sensors utilizing of 1D nanofibers significantly outperform those based on 0D powders by providing higher specific surface area and ohmic I–V characteristics.
“…IR spectra presented in Fig. 6 correspond well with the results published in the literature, especially since the 563 cm −1 band present in the 1D SnO 2 nanostructure in the current study was also reported to exist in 1D structures by others [23]. The presence of this extra absorption band in the 560–570-cm −1 region is known as a characteristic feature of 1D SnO 2 structures, but the nature of their presence still requires clarifications.Fig.…”
Section: Resultssupporting
confidence: 90%
“…There are many papers recently published that study either 0D or 1D nanostructured SnO 2 [ 15 , 16 , 23 , 24 ]. However, the direct comparison of performance of these structurally very different materials is lacking.…”
Zero- and 1D (one-dimensional) tin (IV) oxide nanostructures have been synthesized by thermal evaporation method, and a comparison of their morphology, crystal structure, sorption properties, specific surface area, as well as electrical characteristics has been performed. Synthesized SnO2 nanomaterials were studied by X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM), N2 sorption/desorption technique, IR spectroscopy and, in addition, their current-voltage characteristics have also been measured. The single crystalline structures were obtained both in case of 0D (zero-dimensional) SnO2 powders and in case of 0D nanofibers, as confirmed by electron diffraction of TEM. It was found that SnO2 synthesis parameters significantly affect materials’ properties by contributing to the difference in morphology, texture formation, changes in IR spectra of 1D structure as compared to 0D powders, increases in the specific surface area of nanofibers, and the alteration of current-voltage characteristics 0D and 1D SnO2 nanostructures. It was established that gas sensors utilizing of 1D nanofibers significantly outperform those based on 0D powders by providing higher specific surface area and ohmic I–V characteristics.
“…Considering the accepted value of 3.60 eV for the energy-gap of the SnO 2 nanobelts [19,20] , the ionization energy of the acceptor and the donor level involved in the optical transitions eA° and DAP could also be determined to be, E A = 240 meV and E D1 = 80 meV. The donor level E D1 could also be defined by the IR-UV peaks, 2.07 and 1.47 eV, since both are broad peaks, the value of E D1 obtained was 60 meV, so in order to corroborate with the other transition the donor state were defined to be in the range of E D1 = 60-80 meV.…”
The Persistent Photoconductivity (PPC) effect was studied in individual tin oxide (SnO 2 ) nanobelts as a function of temperature, in air, helium, and vacuum atmospheres, and low temperature Photoluminescence measurements were carried out to study the optical transitions and to determine of the acceptor/donors levels and their best representation inside the band gap. Under ultraviolet (UV) illumination and at temperatures in the range of 200 to 400K we observed a fast and strong enhancement of the photoconductivity, and the maximum value of the photocurrent induced increases as the temperature or the oxygen concentration decreases. By turning off the UV illumination the induced photocurrent decays with lifetimes up to several hours. The photoconductivity and the PPC results were explained by adsorption and desorption of molecular oxygen at the surface of the SnO 2 nanobelts. Based on the temperature dependence of the PPC decay an activation energy of 230 meV was found, which corresponds to the energy necessary for thermal ionization of free holes from acceptor levels to the valence band, in agreement with the photoluminescence results presented. The molecular-oxygen recombination with holes is the origin of the PPC effect in metal oxide semiconductors, so that, the PPC effect is not related to the oxygen vacancies, as commonly presented in the literature.
“…3(B) shows PL emission spectra, the emission peak appearing in all spectra at ~ 366 nm is usually attributed to the free exciton electron hole recombination [8]. The broad emission peak is suggestive of the formation of oxygen deficient nanostructured SnO 2 [9]. It also has been found that as the particle size increases the PL intensity decreases.…”
SnO 2 nanopowders were synthesized by different sol-gel preparation methods using SnCl 4 .5H 2 O and variable concentration of ammonia water as precursor in different solvents in order to obtain different particle size for their gas sensing applications. These nanopowders were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV-Vis spectroscopy and PL spectroscopy. XRD study confirmed the formation of SnO 2 nanoparticles and particle size was estimated using Scherrer's formula. SEM micrographs also suggested the formation of well crystallized, finer grain size and slightly agglomerated nanoparticles. UV-Vis spectroscopy was used to deduce the band gap of nanostructured SnO 2 . PL spectroscopy suggested the formation of oxygen deficient nanostructured SnO 2 . A comparative study of these measurements carried out on synthesized SnO 2 nanopowders by different methods, in order to obtain suitable properties for their gas sensing applications, is presented and discussed in the paper.
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