Nanocrystalline SnO2 Thin Films Research Articles

Effect of Annealing on the Physical Properties of Chemically Synthesized Nanocrystalline SnO2 Thin Films

Effect of Annealing on the Physical Properties of Chemically Synthesized Nanocrystalline SnO2 Thin Films

Surface-disorder and cationic-site defect-induced ferromagnetism and correlated Raman vibrational modes in Sn0.9 In0.1O2 nanocrystalline thin-films

Exploration of magnetism in otherwise nonmagnetic wide-band oxides through defect-engineering has been become a new challenge to achieve the goal of room-temperature ferromagnetic semiconductor for potential applications in spintronics. In this backdrop, we report surface-disorder and cationic-site defect-induced FM in series of Sn0.9In0.1O2 nanocrystalline thin films prepared using pulsed laser deposition different Argon (Ar) pressure. With the increase of deposition pressure, surface morphology of Sn0.9In0.1O2 nanocrystalline thin-films changes as nanoclusters, nanofibres, nanoflakes and nanowires respectively, crystallite size decreases and surface disorder increases gradually. Raman, X-ray photoelectron and Photoluminescence spectroscopic analysis confirm the formation tin-vacancy (VSn) and associated combinational defects that significantly increase the ferromagnetic signal in In-doped SnO2 thin-films. The substitution of trivalent In3+ in Sn site also cause serious lattice distortion which transform the Raman inactive modes A2g and Eu modes into Raman active modes and thus appeared at 574 cm−1 and 354 cm−1 respectively. The nanowires of Sn0.9In0.1O2 are found to possess highest concentration of VSn defects and therefore it exhibits strongest ferromagnetic moment (MS) ∼ 11.1 emu/cm3 and highest Curie temperature (TC) ∼ 572 K. The gradual decrease in carrier concentration with the increasing deposition pressure suggests stabilization of hole-mediated VSn-induced room temperature FM in series of In-doped SnO2 nanocrystalline thin-films.

Reliable liquified petroleum gas sensing at room temperature by nanocrystalline SnO2 thin film deposited by Langmuir–Blodgett method

Reliable liquified petroleum gas sensing at room temperature by nanocrystalline SnO2 thin film deposited by Langmuir–Blodgett method

Room temperature sputtered nanocrystalline SnO2 thin films sensitized with Pd nanoparticles for high performance CO gas sensing application

In the present work, we have reported that Pd sensitized nanocrystalline SnO2 thin films sputtered at room temperature are quite promising for development of CO gas sensors. The investigation of materials quality and to understand the sensing mechanism, various characterization techniques such as the GIXRD, FESEM, PL and XPS were used. The sensing characteristics of prepared samples have been measured for different concentration of CO gas and at different temperatures. An excellent sensor response (∼ 94.5%) has been achieved for Pd sensitized SnO2 at 100 °C temperature for CO gas of 91 ppm concentration than SnO2 thin film (sensor response ∼ 13.6%). The maximum sensor responses ∼ 99.5% and ∼ 84.3% were observed at 200 °C temperature, respectively for both samples. Also, a very fast response and recovery time of about ∼ 8 s and ∼ 15 s was achieved for Pd sensitized SnO2 thin film. Further, it was observed that Pd sensitized SnO2 thin film was highly selective for CO gas compared to NH3, H2S, NO2 and NO gases and highly stable even after preserved for about six months. Thus, rough surface or nano-pillars/cracks on the surface can also improve the gas sensing.

Annealing Effect on Nanocrystalline SnO2 Thin Films Prepared by Spray Pyrolysis Technique

In recent years, a transparent conducting oxide (TCO) SnO2 semiconductor have gained considerable attention due to their potential application in gas sensors. More number of studies on TCO oxide have focused on the semiconducting metal oxides in which an intensive argument is that the transparent semiconductors. The SnO2 thin films were deposited at 400 °C and then annealed at 500 °C and 600 °C and its structural, optical and electrical properties were characterized. The doping stoichiometric ratio was maintained as 4% and the resulting solution was sprayed on glass substrate which was kept at nozzle distance of 25 cm and the spray rate was 10 mL/min. The prepared pure SnO2 thin films have been characterized by different methods such as XRD, FESEM, UV-Vis NIR and EDAX analyses. It was found that the nanocrystalline SnO2 grains possesses structural features of the tetragonal rutile structure. Hence the prepared thin films are justified to be nanocrystalline and also the mean crystalline size decreased with respect to annealing temperature.

A NOVEL pH SENSITIVITY OF SnO2THIN FILM BASED EGFET PREPARED USING CHEMICAL BATH METHOD

Nanocrystalline (NC) tin dioxide (SnO2) thin film has been prepared using chemical bath method at low working temperature onto SiO2/Si substrates. The structural and morphological properties were studied through X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The as-deposited thin film appeared with tetragonal rutile structure. The crystallization of SnO2film was achieved when the film was exposed to anneal at [Formula: see text]C. NC SnO2thin film was successfully utilized as an extended gate field-effect transistor (EGFET) pH sensing. NC SnO2film based pH-EGFET sensor displayed a notable pH sensing performance, where the sensitivity and the linearity values are equal to 25.7 (mV/pH) and 0.8489 within 2–12 range consecutive. The NC SnO2thin film sensor has shown good pH sensor stability and reliability; thus it can be considered the best choice for flexible and disposable biosensors.

Microplotter-Printed On-Chip Combinatorial Library of Ink-Derived Multiple Metal Oxides as an "Electronic Olfaction" Unit.

Information about the surrounding atmosphere at a real timescale significantly relies on available gas sensors to be efficiently combined into multisensor arrays as electronic olfaction units. However, the array's performance is challenged by the ability to provide orthogonal responses from the employed sensors at a reasonable cost. This issue becomes more demanded when the arrays are designed under an on-chip paradigm to meet a number of emerging calls either in the internet-of-things industry or in situ noninvasive diagnostics of human breath, to name a few, for small-sized low-powered detectors. The recent advances in additive manufacturing provide a solid top-down background to develop such chip-based gas-analytical systems under low-cost technology protocols. Here, we employ hydrolytically active heteroligand complexes of metals as ink components for microplotter patterning a multioxide combinatorial library of chemiresistive type at a single chip equipped with multiple electrodes. To primarily test the performance of such a multisensor array, various semiconducting oxides of the p- and n-conductance origins based on pristine and mixed nanocrystalline MnOx, TiO2, ZrO2, CeO2, ZnO, Cr2O3, Co3O4, and SnO2 thin films, of up to 70 nm thick, have been printed over hundred μm areas and their micronanostructure and fabrication conditions are thoroughly assessed. The developed multioxide library is shown to deliver at a range of operating temperatures, up to 400 °C, highly sensitive and highly selective vector signals to different, but chemically akin, alcohol vapors (methanol, ethanol, isopropanol, and n-butanol) as examples at low ppm concentrations when mixed with air. The suggested approach provides us a promising way to achieve cost-effective and well-performed electronic olfaction devices matured from the diverse chemiresistive responses of the printed nanocrystalline oxides.

Thickness dependence of nanocrystalline tin oxide thin films in capacitive biosensor characterization

Nanocrystalline SnO2 thin films of varying thicknesses (250–50 nm) have been prepared on p-type Si by Langmuir Blodgett technique. Nanocrystalline SnO2/polyaniline (Si/SnO2/PANI) thin film heterostructure has been studied for label free, real time electrochemical detection for model immunoglobulin interactions. Sensor responses were studied using impedance methods, wherein transient capacitance gave fast response for antigen-antibody interaction in picomolar concentration range. From the study of sensor structures with varying film thicknesses, it was observed that SnO2 film with less than 200 nm thickness were effected with insulating (dielectric) properties whereas for thickness higher than 200 nm, it was n-type semiconducting characteristics. This is due to effects of charge on the surface adsorbed species as revealed by capacitance voltage characteristics, suggesting these characteristics as indicators of ionic transport effects in nanostructured metal oxide films in electrochemical cell configuration. The current study clearly states the possibility of fabricating cost effective and stable capacitive sensors with SnO2 films with thickness less than 100 nm. The study helps in optimizing the sensing method for capacitive/conductive biosensors based on nanostructured semiconductor thin films.

Low cost preparation technique for conductive and transparent Sb doped SnO2 nanocrystalline thin films for solar cell applications

The spray pyrolysis , as a non-vacuum cost-effective technique was used to develop high-quality thin films of SnO 2 and Sb-doped SnO 2 on Soda-lime glass substrates as transparent conductive oxides (TCOs). The surface morphology of the thin films under study was checked by the atomic force microscope. The average particle size and surface roughness of SnO 2 and Sb-doped SnO 2 thin films mainly depend on the Sb doping level. The structural identification of the as-deposited thin films has been investigated by the X-ray diffraction technique (XRD). XRD patterns have confirmed that the as-deposited thin films have a nanocrystalline structure with the tetragonal phase for all thin-film samples. The optical distribution of the transmittance and absorbance has been studied in a wide range of the wavelength (200–2500 nm). The absorption coefficient , optical band gap, and refractive index have been obtained by using the Swanepoel model. The optoelectronic properties for the thin films under study have been evaluated as TCOs films for photovoltaic applications. The sheet resistance and optical conductivity also have been determined for the thin film under investigation depending on the Sb doping level. • Conductive and transparent films can be obtained by cost-effective spray pyrolysis technique and abundant materials. • X-ray diffraction and atomic force microscope showed the nanocrystalline nature of the SnO 2 and Sb doped SnO 2 films. • The transmission, optical band and sheet resistance values confirm the use of these films as a conductive window layer. • The figure of merit values of these films showed a good opportunity to be applicable in thin-film solar cells.

Singlet Fission and Electron Injection from the Triplet Excited State in Diphenylisobenzofuran–Semiconductor Assemblies: Effects of Solvent Polarity and Driving Force

Singlet fission has emerged as a promising way to overcome the Shockley-Queisser limit in solar energy conversion devices, and a few studies have claimed proof-of-principle results using dye-sensitized photoelectrodes. However, a detailed understanding of what factors govern the fate of the excited state on mesoporous surfaces is still lacking. Here, we have studied how the excitation progresses into singlet fission, electron injection, or formation of molecular charge separated states in diphenylisobenzofuran derivatives with flexible carbon linkers attached to nanocrystalline mesoporous ZrO2, TiO2, and SnO2 thin films. We show that singlet fission occurs for the molecule attached to ZrO2 films when the assembly is immersed in nonpolar solvents, and that singlet fission is hampered by the formation of a molecular charge separated state in more polar solvents. On TiO2 surfaces, direct electron injection from the singlet excited state outcompetes the singlet fission. Instead, triplet formation occurs via charge recombination from the conduction band of TiO2 in nonpolar solvents. When the molecule is attached to SnO2 films, singlet fission partly outcompetes electron injection from the singlet excited state and the two processes occur in parallel. Subsequent to singlet fission on SnO2, triplet injection into the conduction band of SnO2 is observed. The results presented here provide a detailed picture of the singlet fission dynamics in molecules attached to mesoporous semiconductor surfaces, demonstrating that both the semiconductor substrate as well as the environment around the molecules have a large impact, which can be useful in the design of future devices.

Hydrogen gas sensing based on nanocrystalline SnO2 thin films operating at low temperatures

Nanocrystalline (NC) SnO2 thin film has been prepared using sol-gel technique on Al2O3 substrates at low temperature. X-ray diffraction emerged that SnO2 thin film reveals the crystalline nature of NC SnO2 with a tetragonal rutile structure. Field emission scanning electron microscopy image emerged that the morphology of SnO2 thin film is uniform structure a polycrystalline. Hydrogen (H2) gas sensing measurements were performed when the sensor exposed to very low H2 concentration levels in the range 3–100 ppm at operating temperatures ranging from room temperature up to 125 °C. The NC SnO2 thin film sensor was found to be active for H2 sensing, with high sensitivity (48%, 3 ppm and 180%, 100 ppm) respectively at room temperature. Moreover, the sensitivity of the sensor increased with increasing operating temperature, where the sensitivity value at 125 °C (902%, 3 ppm and 3475%, 100 ppm) of H2 gas respectively. The obtained values were significantly higher as compared to the results in the literature. These findings attributed to increasing adsorption/desorption processes of gas molecules that lead to improving sensing properties of a gas sensor.

Controlled optoelectronic properties and abrupt change in photosensitivity by suppressing density of oxygen vacancies in SnO2 nanocrystalline thin films prepared at various spray-deposition temperatures

Nanostructured SnO2 thin films were synthesized at various substrate temperatures using a modified chemical spray pyrolysis (MCSP) technique. The x-ray diffraction (XRD) patterns confirmed the presence of a rutile SnO2 with tetragonal structure for all the resultant film samples. The XRD results ascertained increase in the grain growth rate and consequent enhancement in crystallinity with increasing the spray-deposition temperature. The optical spectroscopic analysis revealed a significant increase in the optical transmission within the visible region as well as a considerable increase in the optical bandgap by increasing the deposition temperature. However, the spectral distribution of the absorption coefficient ascertained the dominance of direct allowed transition for the SnO2 film samples. The analysis of the current-voltage characteristic curves revealed that the variation of the spray-deposition temperature strongly influences the photosensitivity of the film samples. Based on the electrical results, these film samples reveal a semiconductor behaviour of the transport property over the entire investigated range of the working temperature, with two different conduction mechanisms. The optical and electrical results were combined to evaluate the influence of varying the deposition temperature on the figure of merit (FOM) factor for the SnO2 film samples.

Preparation and Characterization of Al doped SnO2 Nanocrystalline Thin Films by Spray Pyrolysis Technique

Preparation and Characterization of Al doped SnO2 Nanocrystalline Thin Films by Spray Pyrolysis Technique

Aviation kerosene sensors based on nanocrystalline SnO2 thin films with various catalysts

Gas-sensitive characteristics of aviation kerosene sensors based on nanocrystalline SnO2 thin films with various catalysts have been studied as a function of the operating temperature and gas concentration in the air. Thin tin dioxide films were grown in magnetron by sputtering of a tin–antimony alloy target in oxygen–argon plasma. It is shown that the sensors are characterized by a high sensitivity to aviation kerosene vapors and by a good stability of parameters during long-term tests and under the variation of humidity.

Synthesis, Characterization And Gas Sensing Performance Of Sol-Gel Prepared Nanocrystalline Sno2 Thin Films

abstract Nanocrystalline SnO2 thin films were successfully prepared using sol-gel dip coating technique. The starting precursor was used as tin chloride dihydrate (SnCl2.2H2O), ethanol and glycerin. As the prepared films were fired at 500oC. These films were characterized using XRD, FE-SEM and TEM to known crystal structure, surface morphology and microstructure property. Elemental composition was studied using energy dispersive spectrophotometer (EDAX). The H2 gas sensing performance of nanocrystalline SnO2 thin films were investigated and presented. It was found that the nanocrystalline SnO2 thin films gives maximum gas response (S= 360) at 75 oC. The sensor shows fast speed of response (TResponse = 2 s) and quick recover (Trecover = 8 s).

Hydrogen Gas Sensing Characterizations Based on Nanocrystalline SnO<sub>2</sub> Thin Films Grown on SiO<sub>2</sub>/Si and Al<sub>2</sub>O<sub>3</sub> Substrates

High-quality nanocrystalline (NC) SnO2 thin films were grown on SiO2/Si and Al2O3 substrates using sol–gel spin coating method. The structural properties, surface morphologies and gas sensing properties of the NC SnO2 were investigated. XRD measurements showed a tetragonal rutile structure and the diffraction peaks for NC SnO2 thin films grown on Al2O3 substrates outperformed those of NC SnO2 films grown on SiO2/Si substrates. The surface morphology of the annealed SnO2 thin films at 500 °C appeared as polycrystalline with uniform nanoparticle distribution. Hydrogen (H2) gas sensing performance of the NC SnO2 was examined for H2 concentrations ranging from 150 ppm to 1000 ppm at different temperatures (room temperature, 75 and 125 °C) for over 50 min. The room temperature sensitivities for H2 gas sensors based on NC SnO2 thin films grown on Al2O3 and SiO2/Si substrates was 2570% and 600%, respectively upon exposure to 1000 ppm of H2 gas. While the sensitivity values at 125 °C increased to 9200% and 1950%, respectively.

Influence of multilayer deposition on characteristics of nanocrystalline SnO2 thin films produce by sol-gel technique for gas sensor application

Nanocrystalline SnO2 thin films have been prepared on glass substrates using sol-gel dip-coating technique. The deposited films were annealed in air at 500°C for one hour. Structural, optical, electrical, and sensing properties of the films were studied for different number of layers. X-ray diffraction spectra reveal the polycrystalline nature of the SnO2 films with tetragonal crystal structure, and have preferred growth direction along (110). The crystallite size of the thin films increased with increasing number of layers. AFM and SEM results indicated that the average grain size increased as number of layers increased. The optical band gap energy and transmittance of dip-coated films decreased as number of layers increased. The electrical properties of SnO2 films include DC electrical conductivity, showing that the films have two activation energies, namely, Ea1 and Ea2, which increase as number of layers increases. The films were further investigated in terms of their sensing abilities for carbon monoxide (CO) and nitrogen dioxide (NO2) gases at 50ppm by measuring their sensitivity to these gases at different times and temperatures. Our results demonstrated that dip-coated prepared films were highly sensitive to CO and NO2 at 200°C.

Microstructural properties and carrier transport mechanism in Bi-doped nanocrystalline SnO2 thin films

Tin oxide (SnO2) thin films, doped with different concentrations of bismuth (Bi), are prepared by the magnetron reactive sputtering technique. Microstructural, spectroscopic and electric transport measurements are performed and the results have been correlated. The crystallite size, which is evaluated from power X-ray diffraction (XRD) studies is in the 10–20nm range. Bi is doped into SnO2 lattice as +5 valence state, leading to n type conductivity. The doped samples show the deterioration of the crystallinity with increase in Bi doping concentration, evidenced by the smaller crystallites and rougher surface compared with undoped ones. Due to highly disordered defects in the Bi-doped SnO2 films, the first order Raman-active mode inherent to SnO2 lattice shifts to lower wavenumber with the increasing of the Bi concentration. Based on Hall effect measurements, it is found that the sheet resistance dramatically increases up to 3.2×104Ω/□ with Bi doping level of 2at.%, accompanied by a sharp decrease of the electron mobility μ. The temperature dependence of the resistance presents different functional relationship relying on the doping concentration, and a possible crossover of the carrier transport mechanism from 2D to 3D behavior is established when discussed in the framework of the weak localization and electron-electron interactions.

Metal–organic-framework derived porous conducting frameworks for highly efficient quantum dot-sensitized solar cells

Metal–organic-framework (MOF) derived carbon framework was buried inside nanocrystalline SnO2thin film as an electron highway to increase the transporting rate of electrons in QD-sensitized thin film.

Acetone and Ethanol Sensors Based on Nanocrystalline SnO2 Thin Films with Various Catalysts

The electrical and gas-sensitive characteristics of sensors based on nanocrystalline SnO2 thin films with noble metals (Pt, Pd, Au) and 3d-transition metals (Co, Ni) additives in the bulk and on the surface have been studied. Thin (~100 nm) tin dioxide films were grown in magnetron by DC sputtering of a tin–antimony alloy target in oxygen–argon plasma. It was shown that the obtained sensors can detect acetone and ethanol vapors at 1 ppm level. The detecting of acetone vapors needs higher temperatures than detecting of ethanol. In a temperature range T 700 K, the sensors with deposited Pt, Pd catalysts on the surface as well as the sensors with Ni and Co additives in the bulk are characterized by a higher sensitivity to acetone than to ethanol. The use of different operating temperatures allows detecting selectively acetone and ethanol vapors.