Nanocrystalline Tin Oxide Research Articles

Nanocrystalline SnO2 thin films: Structural, morphological, electrical transport and optical studies

Sol–gel spin coating method has been successfully employed for preparation of nanocrystalline tin oxide (SnO2) thin films. The effect of processing temperature on the structure, morphology, electrical conductivity, thermoelectric power and band gap was studied using X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction pattern, atomic force microscopy, two probe technique and UV–visible spectroscopy. X-ray diffraction (XRD) analysis showed that SnO2 films are crystallized in the tetragonal phase and present a random orientation. Field emission scanning electron microscopy (FESEM) analysis revealed that surface morphology of the tin oxide film consists nanocrystalline grains with uniform coverage of the substrate surface. Transmission electron microscopy (TEM) of SnO2 film showed nanocrystals having diameter ranging from 5 to 10nm. Selected area electron diffraction (SAED) pattern confirms tetragonal phase evolution of SnO2. Atomic force microscopy (AFM) analysis showed surface morphology of SnO2 film is smooth. The dc electrical conductivity showed the semiconducting nature with room temperature electrical conductivity increased from 10−7 to 10−5 (Ωcm)−1 as processing temperature increased from 400 to 700°C. Thermo power measurement confirms n-type conduction. The band gap energy of SnO2 film decreased from 3.88 to 3.60eV as processing temperature increased from 400 to 700°C.

Elaboration and high resolution TEM characterization of SnO2 nanowires

Graphical abstractDisplay Omitted Highlights? SnO2 nanowires were synthesized by electrodeposition and oxidation in AAO template. ? The growth mechanism of Sn nanowires is a brick-stacked wirelike growth. ? SEM and TEM studies have shown the uniform structures of these nanowires. ? Tetragonal SnO2 phase has been identified by XRD and confirmed by HRTEM. ? HRTEM image shows polycrystalline nanowire with grains size equal to 5nm. Tin dioxide is a wide-band gap (3.6eV) semiconductor with numerous potential applications in batteries, gas sensors, and dye-sensitized solar cells. In this study nanocrystalline tin oxide nanowires have been synthesized by electrochemical deposition and oxidation in anodic aluminum oxide template. Electrochemical synthesis has been controlled by chronoamperometry and oxidation by X-ray diffraction. Polycrystalline nanowires with 140nm in diameter and 3µm in length have been obtained. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies have highlighted a uniform nanowire structure. High resolution transmission electron microscope (TEM FEI Tecnai G2-20 twin) was employed to characterize the crystalline structure of 5nm diameter tin oxide grains. Tetragonal tin oxide phase has been characterized by X-ray powder diffraction and the interplanar distance of 0.32nm corresponding to the SnO2 crystal obtained by HRTEM has confirmed the structure.

Nano-environment effects on the luminescence properties of Eu3+-doped nanocrystalline SnO2 thin films

Nanocrystalline tin (IV) oxide thin films doped with Eu(3+) ions are synthesized using a simple spin-coating method followed by postannealing in an O(2) flow at 700 °C. Transmission electron microscopy and x-ray photoelectron spectroscopy studies illustrate the incorporation of Eu(3+) ions in the films with a high atomic percentage of 2.7%-7.7%, which is found to be linearly dependent on the initial concentration of Eu(3+) in the precursor solution. Glancing incidence x-ray diffraction results show that the crystalline grain sizes decrease with increasing the Eu(3+) concentration and decreasing the postannealing temperature with the emergence of the Eu(2)Sn(2)O(7) phase at high Eu(3+) concentrations (≥5.3 at.%). Luminescence spectra of these doped samples show the characteristic narrow-band magnetic dipole emission at 593 nm and electric dipole emission at 614 nm of the Eu(3+) ions, arising from UV absorption at the SnO(2) band-edge followed by energy transfer to the emission centers. Manipulating the crystallite size, composition, and defect density of the samples greatly affects the absorption edge, energy transfer, and therefore the emission spectra. These modifications in the environment of the Eu(3+) ions allow the emission to be tuned from pure orange characteristic Eu(3+) emission to the broadband emission corresponding to the combination of strong characteristic Eu(3+) emission with the intense defect emissions.

Effect of stirring time on size and dielectric properties of SnO2 nanoparticles prepared by co-precipitation method

Chemical co-precipitation method is employed to examine the effect of stirring time on particle size and dielectric properties of SnO2 nanoparticles. XRD patterns followed by Rietveld analysis revealed the as-prepared SnO2 samples to be pure tetragonal (P42/mnm) with rutile structure. The average crystalline size increases from 26nm to 32nm as the stirring time is increased from 5min to 20min and is confirmed from TEM measurements. The appearance of additional Raman peak at about 540, 574 and 696cm−1 is an indicative of the characteristic of crystal symmetry due to the nano-size and agglomeration of grains in nanocrystalline tin oxide. XPS analysis reveals that in SnO2 Sn exist in 4+ oxidation state. The dielectric constant and loss tangent of 5min stirred SnO2 sample is greatest as compared to samples prepared at increased stirring time.

Swift heavy ion induced topography changes of Tin oxide thin films

Monodisperse tin oxide nanocrystalline thin films are grown on silicon substrates by electron beam evaporation method followed by 100MeV silver ion bombardment with varying ion fluence from 5×1011 ionscm−2 to 1×1013 ionscm−2 at constant ion flux. Enhancement of crystallinity of thin films with fluence is observed from glancing angle X-ray diffraction studies. Morphological studies by atomic force microscopy reveal the changes in grain size from 25nm to 44nm with variation in ion fluence. The effect of initial surface roughness and adatom mobility on topography is reported. In this work correlation between ion beam induced defect concentration with topography and grain size distribution is emphasized.

Photoluminescence Studies on Nanocrystalline Tin Oxide Powder for Optoelectronic Devices

Nanocrystalline tin oxide (SnO2) powders have been synthesized by a low temperature chemical precipitation method. As-prepared and heated powders were characterized by XRD, SEM and luminescence studies. Crystallographic parameters such as crystallite size, lattice parameters and dislocation density in SnO2 nanocrystalline powders were calcu- lated by Rietveld analysis. The average crystallite size of 9 - 43 nm was obtained for SnO2 powders through controlled heat treatment process. The washed powders morphology was almost spherical in shape and average agglomerate crystal size was between 0.2 - 0.4 μm. A Photoluminescence (PL) study was measured at an excitation wavelength of 265 nm for as-prepared and annealed powders; it showed a broad emission peak at 417 nm for all powders. The highest PL emission was attained for the powder annealed at 500℃. The synthesized nanocrystalline SnO2 oxide semiconductor material could be suitable for making optoelectronic and sensor devices.

Synthesis and Characterization of Nano Crystalline Tin(IV) Oxide from Tin(II) Chloride Using Combined Microwave and Traditional Calcinations Procedures

Synthesis and Characterization of Nano Crystalline Tin(IV) Oxide from Tin(II) Chloride Using Combined Microwave and Traditional Calcinations Procedures

Pulsed direct current magnetron sputtered nanocrystalline tin oxide films

The nanocrystalline tin oxide (SnO2) films were deposited on glass substrates by pulsed magnetron sputtering technique and subsequently annealed from 200 to 500°C. The structural, microstructural, electrical, and optical properties of as deposited and annealed SnO2 films were studied. The crystallinity degree of the films increased with annealing temperature. Photoluminescence (PL) measurements showed that the emission peaks have low intensity and are positioned at 535nm (2.31eV) and 605nm (2.05eV) in as deposited SnO2 films. The intensity of PL peak increases sharply with the increasing of annealing temperature. The as deposited films exhibited high electrical resistivity and low optical transmittance. After annealing at 500°C, the electrical resistivity of the films decreased to the lowest value of 0.015Ωcm, being the optical transmittance 90%.

Studies on the resistive response of nickel and cerium doped SnO2 thick films to acetone vapor

Undoped and Ni, Ce-doped nanocrystalline tin oxide were synthesized by co-precipitation route. Doped as well as undoped SnO2 compositions revealed single phase structure without any impurity. The lattice constant of SnO2 increases and the grain size decreases with doping of Ni and Ce. The responses of the sensing elements are evaluated by measuring the resistance change upon exposure to various test gases such as liquid petroleum gas (LPG), acetone, ethanol and ammonia. In comparison to LPG, ethanol, and ammonia the response towards acetone vapor increases markedly on simultaneous doping of Ni and Ce. For acetone vapors with 500ppm at 300°C, the undoped SnO2 shows 31% response, while with individual Ni or Ce doping it increases to 38 and 60%, respectively, however with simultaneous doping of Ni and Ce there is a significant enhancement up to 92%. The results of gas sensing measurements reveal that the thick films deposited on alumina substrates using screen printing technique give selectively a high response of (87%) with fast recovery (∼1min) towards 100ppm acetone at 300°C.

Effect of propylene carbonate as a plasticizer on (PEO)50AgCF3SO3:SnO2 nanocomposite polymer electrolyte

This work deals with the incorporation of propylene carbonate (PC) as a plasticizer in conjunction with poly (ethylene oxide) (PEO), silver triflate (AgCF3SO3) and nanocrystalline tin oxide (SnO2) for obtaining the nanocomposite polymer electrolyte system (PEO)50AgCF3SO3:2 wt% SnO2 + x wt% PC (x = 10, 20, 30 and 40) by solution casting method. The present electrical conductivity data extracted by means of complex impedance spectroscopic analysis in the frequency range 20 Hz–1 MHz and over the temperature domain 298–373 K have demonstrated that the maximum electrical conductivity value of 5.9 × 10−5 S cm−1 at 298 K would be possessed by the specimen containing 30 wt% PC incorporated into the optimized nanocomposite system (PEO)50AgCF3SO3:2 wt% SnO2. Silver ionic transference number (tAg+) data evaluated using AC/DC polarization technique have indicated that the highest tAg+ value of 0.52 could be realized in the case of the specimen (PEO)50AgCF3SO3:2 wt% SnO2 + 30 wt% PC, whereas the complexation of the plasticizer within the nanocomposite electrolyte has been deduced from the detailed Fourier transform infrared spectroscopic investigation owing to the fact that such results have revealed the appearance of absorption bands corresponding to free triflate ions (CF3SO3−) and PC. Surface morphological features of pure PEO and (PEO)50AgCF3SO3:2 wt% SnO2 + 30 wt% PC nanocomposite systems were analysed through scanning electron microscope. The feasibility of a reduction in the degree of crystallinity of the plasticized system has been indicated by the X-ray diffraction data and confirmed from differential scanning calorimetric results obtained in terms of quantification of crystallinity and reduction in the glass transition temperature due to the addition of the chosen plasticizer into the nanocomposite polymer electrolyte matrix. Interestingly, the all solid-state cell based on the nanocomposite polymer electrolyte, namely, (PEO)50AgCF3SO3:2 wt% SnO2 + 30 wt% PC and silver anode has exhibited an open circuit voltage of 676 mV and short circuit current of 192 μA at room temperature.

Temperature dependent structural and optical properties of tin oxide nanoparticles

Nanocrystalline tin oxide (SnO2) powders were synthesized through wet chemical route using tin metal as precursor. The morphology and optical properties, as well as the effect of sintering on the structural attributes of SnO2 particles were analyzed using Transmission electron microscopy (TEM), UV–visible spectrophotometry (UV–vis) and X-ray diffraction (XRD), respectively. The data revealed that the lattice strain plays a significant role in determining the structural properties of sintered nanoparticles. The particle size was found to be 5.8nm, 19.1nm and 21.7nm for samples sintered at 300°C, 500°C, and 700°C, respectively. Also, the band gaps were substantially reduced from 4.1eV to 3.8eV with increasing sintering temperatures. The results elucidated that the structural and optical properties of the SnO2 nanoparticles can be easily modulated by altering sintering temperature during de novo synthesis.

Strong metal–support interaction as activity requirement of palladium-supported tin oxide sol–gel catalyst for water denitration

Two nanocrystalline palladium-supported tin oxide catalysts for water denitration were synthesized by a modified sol–gel technique using appropriate chloride precursors for both support and active phases, and citric acid to tune the rate of hydrolysis and condensation. The difference among sample preparation procedures refers to the moment of the noble metal loading to the support, as well as to the calcination temperature altitude followed. Thus, mesoporous tin oxide was synthesized by a sol–gel method following calcination at 700°C. The palladium active phase was introduced afterwards by means of palladium chloride solution impregnation, followed by calcination at 400°C (sample 1). Alternatively, simultaneous complexation of both metal and support precursors followed by single calcination at 700°C was applied for preparation of sample 2. The former sample showed higher activity and selectivity in hydro-denitration of water model system initially containing 100 ppm of nitrates. This was explained by preferential textural, morphological and structural properties accomplished by early contact of metal and support nanoparticles, while achieved by calcination at high single temperature forcing diffusion of palladium ions into the tin oxide matrix. The outcome is very well distribution of palladium and strong metal–support interaction leading to multivalent tin. This indicates partly reduced tin oxide formation in the course of its reduction in hydrogen, which may act as active site in denitration reaction.

NANOCRYSTALLINE TIN OXIDE THIN FILM AS A LOW LEVEL H2S GAS SENSOR

Tin oxide thin films were deposited on alumina substrates at 350°C by spray pyrolysis technique. The films were studied after annealing them in air at different temperatures 550°C, 750°C and 950°C for 30 min. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical absorption spectroscopy technique. The grain size was observed to be increased, ranging from 40 to 56.1 nm, with the increase in annealing temperature. Absorbance spectra were taken to examine the optical properties. The band gap energy was observed to be decreased with the increase in annealing temperature. These films were tested to various gases at different operating temperature ranging from 50°C to 450°C. The Tin Oxide film showed maximum sensitivity to H2S gas. The H2S sensing property of the SnO2 films was investigated with different annealing temperatures of the films and at different concentrations of H2S gas. It was found that the annealing temperature of the film significantly affects the sensitivity of the SnO2 to the H2S gas. The maximum sensitivity was found in case of the film annealed at temperature 950°C at the operating temperature 100°C. The sensitivity was found to be increased by 24% in case of the film annealed at 950°C as compared to the sensitivity of the film annealed at 550°C. The observed response of the film was for gas concentration of 10 ppm for H2S with reasonable sensitivity. The quick response and fast recovery are the main features of this film. The effect of annealing temperature on the structural, microstructural, optical and gas sensing properties of the nanocrystalline tin oxide thin films were studied and discussed.

Optical generation of free charge carriers in nanocrystalline tin oxide for gas sensor application

Nanocrystalline films of tin oxides SnO 2 with nanocrystal sizes of about 100 nm and thickness of 600 nm prepared by thermal oxidation of metallic tin layers were investigated by using the infrared (IR) spectroscopy, Raman scattering and current–voltage measurements in different molecular environments. An increase of the absorption in the middle IR spectral range was detected at room temperature after illumination of the samples by UV light with photon energy of 3.3 eV, which was below the band gap of SnO 2 . The effect was explained as an evidence of the absorption by non-equilibrium free charge carriers (electrons) in SnO 2 nanocrystals. The concentration of photo-generated free charge carriers was calculated from the IR-spectroscopy data according to the Drude model and it was up to 10 18 cm −3 . An effect of the molecular adsorption of iodine on the electrical conductivity of the films was investigated by current–voltage measurements, which revealed a strong increase of the sensor response for nanocrystalline SnO 2 under the UV excitation at room temperature. Possible mechanisms of the observed photo-generation of free charge carriers in SnO 2 nanocrystals and feasible applications of this effect in gas sensors are discussed.

The effect of substrate temperature on the electrical and optic properties of nanocrystalline tin oxide coatings produced by APCVD

Tin oxide thin films were grown by atmospheric pressure chemical vapor deposition (APCVD) on glass substrates at temperatures of 400, 500 and 600 °C with various deposition times from 15 to 60 min with 15 min time intervals. A homemade horizontal reactor was used for deposition from SnCl 2+2H 2O precursors with pure oxygen flowing at a rate of 5 ccpm. Optical and electrical properties were studied for determining the relationship between physical properties and production parameters of the resultant thin films. The structure was analyzed by scanning electron microscopy and X-ray diffraction methods. Electrical and optical properties were studied to determine resistivity, visible light transmission and infrared transmission optical transmittance of the coatings for different, specific application areas.

Effect of doping level on physical properties of antimony doped nanocrystalline tin oxide films fabricated using low cost spray technique

Antimony doped nanocrystalline tin oxide (SnO2∶Sb) films have been fabricated using a low cost and simple fabrication technique using a perfume atomiser. The X-ray diffraction patterns of the antimony doped tin oxide (ATO) films show that the films are polycrystalline with tetragonal cassiterite structure having (110) plane parallel to the surface of the substrate. The preferred orientation remains constant for all the doping levels (0·5–3·0 at-%) and the degree of preferred orientation increases with increasing doping concentration in the starting solution. The intensity of the (110) plane steadily increases as the doping concentration of antimony increases. The fine quality of AFM images show that the films have homogeneous and uniform surface. The sheet resistance is found to decrease with increasing antimony doping level, attain a minimum value (6·34 Ω sq−1) when the doping concentration is 2·5 at-% and then increase for further doping.

Nanomaterial Preparations by Microwave-Assisted Solution Combustion Method and Material Properties of SnO<sub>2</sub> Powder - A Status Review

A nanocrystalline tin oxide (SnO2) powders have been prepared by a simple, low-temperature initiated, self-propagating and gas producing by microwave-assisted solution combustion process. The effects of temperature on crystalline phase formation and particle size of nanocrystalline SnO2 and its structure have been investigated. It is observed that heat-treated upto 800°C shows tetragonal phase SnO2. It was observed that the average crystallite size of the annealed SnO2 samples is in the range 9 - 43 nm through controlled heat treatment process. The crystal density of the as-prepared powder is 5.850g cm-3 where as the bulk density is 6.998 g cm−3. The microstructure and morphology were studied by scanning electron microscope (SEM) and HRTEM it is interesting to note that as-prepared SnO2 sample are almost spherical in shape and average agglomerate crystal size of 0.2 – 0.4 μm with increase in calcination temperature, the samples become better morphology than the as-prepared sample. The crystallographic parameters were refined by XRD pattern and Rietveld refinement using TOPAS-3 and Diamond software was used to construct the structural parameters.

Tracing the Incorporated Fluorine in Spray Deposited Nanocrystalline Tin Oxide Thin Film

Tracing the Incorporated Fluorine in Spray Deposited Nanocrystalline Tin Oxide Thin Film

EXAFS and Raman scattering studies of Y and Zr doped nano-crystalline tin oxide

Nanocrystals of Y and Zr doped SnO2 have been prepared by sol-gel route and annealed at 200, 400, 600, 800 and 1000 ºC. The X-ray diffraction (XRD) results showed the average size of the particles in the freshly prepared samples to be ~ 3 nm. The Extended Absorption Fine Structure (EXAFS) technique was used to study the dopant environments in nanocrystalline tin oxide. In all Y-doped samples, except the one annealed at 1000 ºC, there is clear evidence that Y has not entered the SnO2 lattice. This is clearly supported by the Raman scattering results. In all Zr-doped samples, there is a simple substitution for Sn by Zr.

Effect of post-annealing temperature on nano-structure and energy band gap of indium tin oxide (ITO) nano-particles synthesized by polymerizing–complexing sol–gel method

In this paper, we report on the structural, microstructural and optical properties of nano-crystalline indium tin oxide (ITO) particle, which has been synthesized by sol–gel process using a simple starting hydro-alcoholic solution consisting of In(NO 3) 3.5H 2O, SnCl 4.5H 2O, citric acid as complexing and ethylene glycol as polymerization agents. The structural properties of indium tin oxide nano-powders annealed at different temperatures ( T=350–650 °C) have been characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. The XRD patterns show In 2O 3-cubic phase in nano-powders without any indication of crystalline SnO x as an additional phase. The TEM images show the nano-particles as nearly spherical shaped with size in the range of 10–45 nm as the size of grains increases by increasing the annealing temperatures. The optical direct band gap of ITO nano-particles was calculated to be about 3.39–4.02 eV in the temperature range 350–650 °C by optical absorption measurements. The optical band gap shifts to a higher energy with increasing annealing temperature is due to the improvement of the crystallinity, thereby increasing the carrier concentration as determined from the Burstein–Moss effect.