Nanostructured Tin Oxide Films Research Articles

Nanostructured tin oxide films: Physical synthesis, characterization, and gas sensing properties

Nanostructured tin oxide (SnO2) films are synthesized using physical method i.e. thermal evaporation and are further characterized with X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy measurement techniques for confirming its structure and morphology. The chemiresistive properties of SnO2 films are studied towards different oxidizing and reducing gases where these films have demonstrated considerable selectivity towards oxidizing nitrogen dioxide (NO2) gas with a maximum response of 403% to 100ppm @200°C, and fast response and recovery times of 4s and 210s, respectively, than other test gases. In addition, SnO2 films are enabling to detect as low as 1ppm NO2 gas concentration @200°C with 23% response enhancement. Chemiresistive performances of SnO2 films are carried out in the range of 1–100ppm and reported. Finally, plausible adsorption and desorption reaction mechanism of NO2 gas molecules with SnO2 film surface has been thoroughly discussed by means of an impedance spectroscopy analysis.

Characterization of Nano-Structured Tin Oxide Film Prepared by Anodic Oxidation Process

In this study, synthesis of tin oxide by anodic oxidation of tin foils at room temperature in oxalic acid has been investigated. The prepared structure was characterized by field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). FESEM results showed that the anodization process leads to formation of nanoporous, cuboid and granular structures. EDS analysis in all tested samples showed the constituents of tin and oxygen.

Surfactant assisted growth of nanostructured tin oxide films for gas sensing applications

Porous nanostructured SnO2 films have been prepared using an ultrasonic spray pyrolysis technique in conjunction with cationic, anionic and non ionic surfactants namely CTAB (Cetyl trimethyl ammonium bromide), SDS (sodium dodecyl sulphate) and PEG (polyethylene glycol) respectively. The effect of surfactants on the structural, electrical, optical and gas sensing properties of SnO2 films were investigated by using different techniques such as X-ray diffraction (XRD), Field emission scanning electroscope microscopy (FESEM), two probe technique and Photoluminiscence (PL) studies. The results reveal that the addition of surfactants in the precursor solutions leads to reduction in crystallite size with significant changes in porosity of SnO2 films. PL studies of the films show emissions in the visible region which exhibit changes in the intensities upon variation of surfactants in the precursor solutions. The prepared films were tested for their sensing behaviour towards chlorine and the results reveal that the films prepared in conjunction with cationic surfactant CTAB exhibits a sensing response of 53.5% towards 20 ppm chlorine at a low operating temperature of 150°C.

Photosensitivity Characterization of Nanostructured Tin Oxide Films and Alternative Photodetector Application

In this paper, we present an analysis of the photosensitivity property of electrical resistance of nanostructured porous tin oxide films (SnO2) deposited on Si substrates using a spray method. Based on this property, we propose a new application for this material as an element in a photodetector device. As we verified that the film photosensitivity is influenced by room temperature, to develop a photodetector device, we propose a microcontroller-based algorithm for compensating temperature changes in a certain range. The morphological and chemical structure of the sample films revealed by atomic force microscopy (AFM) and Raman spectroscopy are also discussed. The dynamics of the photodetector have been tested by varying the frequency of light excitation and the temperature of the film. The results show that the device works properly for intermediate ranges of frequency and temperature, but its response degrades as the frequency or temperature rises.

Sol–Gel Derived Nanostructured Tin Oxide Film for Glucose Sensor

Sol–Gel Derived Nanostructured Tin Oxide Film for Glucose Sensor

SnO 2 thin-films prepared by a spray–gel pyrolysis: Influence of sol properties on film morphologies

Nanostructured tin oxide films were prepared by depositing different sols using the so-called spray–gel pyrolysis process. SnO 2 suspensions (sols) were obtained from tin (IV) tert-amyloxide (Sn( t-OAm) 4) or tin (IV) chloride pentahydrate (SnCl 4·5H 2O) precursors, and stabilized with ammonia or tetraethylammonium hydroxide (TEA-OH). Xerogels from the different sols were obtained by solvent evaporation under controlled humidity. The Relative Gelling Volumes (RGV) of these sols strongly depended on the type of precursor. Xerogels obtained from inorganic salts gelled faster, while, as determined by thermal gravimetric analysis, occluding a significant amount of volatile compounds. Infrared spectroscopic analysis was performed on raw and annealed xerogels (300, 500 °C, 1 h). Annealing removed water and ammonium or alkyl ammonium chloride, increasing the number of Sn–O–Sn bonds. SnO 2 films were prepared by spraying the sols for 60 min onto glass and alumina substrates at 130 °C. The films obtained from all the sols were amorphous or displayed a very small grain size, and crystallized after annealing at 400 °C or 500 °C in air for 2 h. X-ray diffraction analysis showed the presence of the cassiterite structure and line broadening indicated a polycrystalline material with a grain size in the nanometer range. Results obtained from Scanning Electron Microscopy analysis demonstrated a strong dependence of the film morphology on the RGV of the sols. Films obtained from Sn( t-OAm) 4 showed a highly textured morphology based on fiber-shape bridges, whereas the films obtained from SnCl 4·5H 2O had a smoother surface formed by “O-ring” shaped domains. Lastly, the performance of these films as gas sensor devices was tested. The conductance (sensor) response for ethanol as a target analyte was of the same order of magnitude for the three kinds of films. However, the response of the highly textured films was more stable with shorter response times.

Core-shell Pd nanoparticles embedded in SnOx films. Synthesis, analytical characterisation and perspective application in chemiresistor-type sensing devices

A two-step bottom up preparation protocol is proposed as a useful tool for the controlled modification of tin oxide films by means of Pd nanoparticles (PdNPs). Colloidal palladium is prepared via an electrolytic process that affords for a core-shell particle structure, while nanostructured tin oxide films are prepared following a sol–gel process. Pd/SnOx composite layers are obtained adding a proper aliquot of pre-formed PdNPs to the tin oxide precursor solution. The nanomaterials surface chemical composition is addressed by X-ray Photoelectron Spectroscopy. Preliminary results on the application of Pd/SnOx as active layers in chemiresistor-type gas-sensing devices are reported, as well.

SnO 2 nanostructured films obtained by pulsed laser ablation deposition

Nanostructured tin oxide films were deposited on Si(1 0 0) substrates at room temperature using the PLAD method. Depositions were achieved by using a XeCl * laser, with a fluence of 10 J/cm 2 to ablate a SnO 2 target either in vacuum or in an atmosphere containing a relatively low partial pressure (10 −2 to 100 Pa) of O 2. A range of spectroscopic diffraction and real space imaging techniques, SEM, EDS, XRD, and XPS were used in order to characterize the surface morphology, structure, and composition of films. XPS results indicate that the film deposited in vacuum comprises a mixture of Sn, SnO and SnO 2. In contrast, films deposited in oxygen comprise only SnO and SnO 2. This indicates that the deposition of tin oxide films in relatively low partial pressures of O 2 prevents the accumulation of unreacted tin metal within the resulting film. SEM studies reveal a sub-micron grain size structure, while XRD analyses indicate that the samples are crystalline, with no evidence for the presence of amorphous material. In this paper we discuss the significance and implications of these findings in terms of the optimization of tin oxide films for use in gas sensing devices and other technological applications.

Buffer layer effect in nanostructured tin electrodeposition on insulating and conducting substrates

The electroplating techniques for metal aggregates and films deposition commonly use an electric current to reduce metal ions in solution, but are restricted to conducting substrate. This new electrochemical technique permits coating of insulating or conducting substrates with metals having controlled aggregate size and growth speed. The basis of our approach is the progressive outward growth of the metal from an electrode in contact with the substrate, with the cell geometry chosen in such a way that the electron current providing the reduction passes through the growing deposit. The nanostructured deposit is composed of branched nanoaggregates from a quasi-continuous film to a more dendritic morphology dependant on current conditions. This approach has been used to elaborate tin electrodeposited thin films composed of a homogeneous distribution of nanoparticles on conducting or insulating substrates. In our works, when a non-continuous buffer gold coating is used, spontaneous mixing of tin atoms into AuSn nanoparticles takes place even at room temperature forming a nanostructured fractal film, if the substrate is conducting or insulating. Without a gold buffer layer , the deposit is composed of large pure tin micro-crystals with a large size distribution, less adapted to tin oxide nanoparticle formation. Indeed, from these tin metal deposits, the final goal is to elaborate functional nanostructured tin oxide films by oxidation for gas sensor applications .

Preparation and Characterization of Nanostructured Tin Oxide Films by Electrochemical Deposition

In this study, a novel process for depositing tin oxide thin films by electrodeposition has been developed. Amorphous phase of the as-deposited film was obtained at the temperature of 85°C. Nanocrystalline having tetragonal structure with a grain size in the range of 4 to 7 nm was obtained by heat-treatment at 400°C in a vacuum for 4 h. Porous, dense, and uniform morphologies for the deposits can be obtained by controlling current density during deposition. Results of infrared spectra, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses were described and correlated with the process of deposition and characteristics of the resulting films. © 2002 The Electrochemical Society. All rights reserved.

Pulsed laser deposition of nanostructured tin oxide films for gas sensing applications

Pulsed laser deposition (PLD) technique has been successfully used to not only deposit nanostructured tin dioxide (SnO 2) thin films, on alumina substrates, but also to concomitantly achieve their in-situ doping by Pt metal catalyst. The deposition of PLD SnO 2 films was investigated at a substrate deposition temperature of 300°C under both vacuum and an oxygen background pressure of 150 mTorr. While the crystalline structure and the composition of the PLD SnO 2 films were systematically determined by means of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, respectively, their morphology and nanostructure were investigated by scanning and transmission electron microscopies (SEM and TEM, respectively). The PLD films deposited under oxygen consist of polycrystalline pure SnO 2 phase, are stoechiometric and exhibit a columnar growth morphology with an apparent inter-columnar porosity. In contrast, those deposited under vacuum consist of a mixture of both a-SnO and poly-SnO 2 phases. TEM observations have revealed that the SnO 2 columns (of few 10 s nm diameter) that constitute the films are, in turn, composed of almost spherical nanograins. On the other hand, the newly developed in-situ doping approach has been shown not only to provide uniform Pt-doping all through the film thickness, but also to be effective in fabricating high-performance gas sensors. A Pt-doping level of ∼2 at.% was identified as the optimal concentration that leads to the highest sensitivity at an operating temperature of the sensors as low as 200°C. The sensing performances of the developed SnO 2 sensors for detecting CO in synthetic air background, over the (10–500 ppm) CO concentration range, are presented.