Deposited Tin Oxide Thin Films Research Articles

Investigations on temperature dependent properties of spray deposited tin oxide thin films

The present study reported the temperature dependent properties of tin oxide (SnO2) thin films deposited by using conventional, cost effective and non-vacuum-based spray pyrolysis technique (SPT). The as deposited films were characterized by various characterization techniques such as X ray diffraction (XRD), UV-Vis spectroscopy and Scanning electron microscopy (SEM) to study their structural, optical and morphological properties respectively. XRD analysis revealed tetragonal rutile crystal structure of SnO2 with preferred orientation along (200) plane. The refinement of XRD data was also carried out by Rietveld refinement to obtain the fitting parameters, crystallite size and lattice parameters. UV-Vis study showed considerable change in optical absorbance and transmittance with change in substrate temperature. Effect of substrate temperature on film thickness, refractive index and band gap energy were determined by Swanepoel method and by Tauc’s plot respectively. The Urbach energy was also calculated and were correlated to the defects in SnO2 films. SEM micrograph showed the transformation from granules to nanospheres as a function of substrate temperature. Electrical properties were determined by Hall effect measurements which gives carrier concentration, electrical resistivity and mobility in the order of 1019-1020 /cm3, 10−2-10−3 Ω.cm and 4–23 cm2/Vs respectively.

Indium Tin Oxide Thin Film Deposition by Magnetron Sputtering at Room Temperature for the Manufacturing of Efficient Transparent Heaters

Indium tin oxide (ITO) thin films are widely used as transparent electrodes in electronic devices. Many of those electronic devices are heat sensitive, thus their manufacturing process steps should not exceed 100 °C. Manufacturing competitive high-quality ITO films at low temperature at industrial scale is still a challenge. Magnetron sputtering technology is the most suitable technology fulfilling those requirements. However, ITO layer properties and the reproducibility of the process are extremely sensitive to process parameters. Here, morphological, structural, electrical, and optical characterization of the ITO layers deposited at low temperature has been successfully correlated to magnetron sputtering process parameters. It has been demonstrated that the oxygen flow controls and influences layer properties. For oxygen flow between 3–4 sccm, high quality crystalline layers were obtained with excellent optoelectronic properties (resistivity <8 × 10−4 Ω·cm and visible transmittance >80%). The optimized conditions were applied to successfully manufacture transparent ITO heaters on large area glass and polymeric components. When a low supply voltage (8 V) was applied to transparent heaters (THs), de-icing of the surface was produced in less than 2 min, showing uniform thermal distribution. In addition, both THs (glass and polycarbonate) showed a great stability when exposed to saline solution.

Origin of Mangetotransport Properties in APCVD Deposited Tin Oxide Thin Films.

Transparent conducting oxides (TCO) with high electrical conductivity and at the same time high transparency in the visible spectrum are an important class of materials widely used in many devices requiring a transparent contact such as light-emitting diodes, solar cells and display screens. Since the improvement of electrical conductivity usually leads to degradation of optical transparency, a fine-tuning sample preparation process and a better understanding of the correlation between structural and transport properties is necessary for optimizing the properties of TCO for use in such devices. Here we report a structural and magnetotransport study of tin oxide (SnO2), a well-known and commonly used TCO, prepared by a simple and relatively cheap Atmospheric Pressure Chemical Vapour Deposition (APCVD) method in the form of thin films deposited on soda-lime glass substrates. The thin films were deposited at two different temperatures (which were previously found to be close to optimum for our setup), 590 °C and 610 °C, and with (doped) or without (undoped) the addition of fluorine dopants. Scanning Electron Microscopy (SEM) and Grazing Incidence X-ray Diffraction (GIXRD) revealed the presence of inhomogeneity in the samples, on a bigger scale in form of grains (80–200 nm), and on a smaller scale in form of crystallites (10–25 nm). Charge carrier density and mobility extracted from DC resistivity and Hall effect measurements were in the ranges 1–3 × 1020 cm−3 and 10–20 cm2/Vs, which are typical values for SnO2 films, and show a negligible temperature dependence from room temperature down to −269 °C. Such behaviour is ascribed to grain boundary scattering, with the interior of the grains degenerately doped (i.e., the Fermi level is situated well above the conduction band minimum) and with negligible electrostatic barriers at the grain boundaries (due to high dopant concentration). The observed difference for factor 2 in mobility among the thin-film SnO2 samples most likely arises due to the difference in the preferred orientation of crystallites (texture coefficient).

Plasma treatment to tailor growth and photoelectric performance of plasma-enhanced atomic layer deposition SnOx infrared transparent conductive thin films

The performance of atomic layer deposition films is mainly limited by precursor residues, low crystallinity and densities due to low deposition temperatures. Here, we used atomic layer deposition to deposit tin oxide thin films at a relatively low temperature of 250 °C. At this temperature, the change in the valence of Sn due to precursor residue is eliminated by layer-by-layer Ar plasma treatment, and the crystallinity of the films is improved. The effects of Ar plasma treatment power and Ar treatment time on the structural and optoelectronic properties were investigated. It was found that Ar plasma treatment time more significantly affects the surface morphology and the optical and electrical properties of the film. The film is transparent to both visible and near-infrared light over a wide range of wavelengths from 400 nm to at least 5000 nm. The film resistivity can be as low as 1.117 × 10−3 Ω·cm. The film has a relatively low level of residual stress due to the fact that there is no need to improve the crystallinity of the film by conventional high temperature annealing. On the basis of the high transparency and high conductivity of the SnOx films with layer by layer Ar plasma treatment in situ, the films can be applied as electromagnetic shielding windows for photodetectors.

Effect of F and Nb co-doping on structural, electrical and optical properties of spray deposited tin oxide thin films

F and Nb co-doped tin oxide films were deposited from monobutyltin trichloride (C4H9SnCl3) on glass substrates at 470 °C by spray pyrolysis. The evolution of the film structure and morphology was investigated by X-ray diffraction and scanning electron microscopy, respectively. All the films were a single phase with polycrystalline, exhibiting a tetragonal cassiterite structure with (200) orientation. The introduction of F and Nb contributed to the growth of the films towards (200) crystal orientation and the formation of pyramidal shape particles with (101) twin planes. Resistivity, carrier concentration, and Hall mobility values of 3.62 × 10−4 Ω cm, 7.463 × 1020 cm−3, and 27.8 cm2 V−1 s−1, respectively, were achieved in the films for a dopant concentration of 20 at.% F and 1 at.% Nb in the precursor solution. Also, the transmittance of all the films in the visible range reached about 80% and the infrared reflectivity was oscillated between 92 and 96%.

SUPERCAPACITOR BEHAVIOR OF SPRAY DEPOSITEDSnO2THIN FILMS

Tin oxide thin films were prepared via spray pyrolysis method. The structural and morphological properties of SnO2thin films have been investigated using X-ray diffraction (XRD) and scanned electron microscope (SEM) analysis. The XRD pattern confirms the tetragonal rutile structure of SnO2with preferential orientation along (200) plane. SEM image reveals the nanocrystalline nature of the SnO2films. SnO2thin films were subjected to electrochemical tests to study the supercapacitor behavior. Maximum specific capacitance of 168 F/g at a scan rate of 25 mV/s was obtained using 0.5 M KOH as the electrolyte. This is the highest value ever reported for spray deposited tin oxide thin films.

Influence of the plasma expansion dynamics on the structural properties of pulsed laser ablation deposited tin oxide thin films

Tin oxide thin films were deposited by pulsed laser ablation at different oxygen partial pressures and substrate temperatures. Information on the structural and morphological properties of the deposited thin films has been obtained by means of X-ray photoelectron, Fourier transform infrared absorption spectroscopies and scanning electron microscopy. The expansion of the laser generated plasma has been studied by means of time resolved fast photography. Different expansion regimes were observed: in vacuum the plasma follows a free expansion one while the raise of the background oxygen pressure leads to the development of a shock wave. It was found that only at 13.3 Pa of oxygen gas, in the presence of a shock wave, the deposition of stoichiometric films, at relatively low substrates temperature, is attainable. The correlation between the observed dynamics of the plasma expansion and the structural properties of the deposited films is presented and discussed.

Influence of annealing on the physical properties of filtered vacuum arc deposited tin oxide thin films

Tin oxide (SnO 2) thin films were deposited on UV fused silica (UVFS) substrates using filtered vacuum arc deposition (FVAD). During deposition, the substrates were at room temperature (RT). As-deposited films were annealed at 400 and 600 °C in Ar for 30 min. The film structure, composition, and surface morphology were determined as function of the annealing temperature using X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The XRD patterns of the SnO 2 thin films deposited on substrates at RT indicated that the films were amorphous, however, after the annealing the film structure became polycrystalline. The grain size of the annealed films, obtained from the XRD analysis, increased with the annealing temperature, and it was in the range 8–34 nm. The AFM analysis of the surface revealed an increase in the film surface average grain size from 15 nm to 46 nm, and the surface roughness from 0.2 to 1.8 nm, as function of the annealing temperature. The average optical transmission of the films in the visible spectrum was >80%, and increased by the annealing ∼10%. The films’ optical constants in the 250–989 nm wavelength range were determined by variable angle spectroscopic ellipsometry (VASE). The refractive indexes of as-deposited and annealed films were in the range 1.83–2.23 and 1.85–2.3, respectively. The extinction coefficients, k( λ), of as-deposited and annealed films were in the range same range ∼0–0.5. The optical energy band gap ( E g), as determined by the dependence of the absorption coefficient on the photon energy at short wavelengths, increased with the annealing temperature from 3.90 to 4.35 eV. The lowest electrical resistivity of the as-deposited tin oxide films was 7.8 × 10 −3 Ω cm, however, film annealing resulted in highly resistive films.

NIR diode laser spectroscopy of HF and HCl at multiple points in the atmospheric pressure CVD of tin oxide films

This paper reports the in situ application, for the first time, of simultaneous multispecies, multipoint near-infrared diode laser absorption spectroscopy (NIRDLAS) to the deposition of thin films by atmospheric pressure chemical vapour deposition (APCVD). Hydrogen fluoride as a precursor and hydrogen chloride as a reaction product were detected in tin oxide thin film deposition in a roll-to-roll pilot reactor. The process is commercially important, and we demonstrate results from the application of the technology to the production scale manufacturing process for photovoltaic coatings.

Electrochemical investigations on spray deposited tin oxide thin films

Tin oxide (SnO 2) thin films were prepared by a simple and inexpensive spray pyrolysis technique from an aqueous solution at various substrate temperatures viz. 300, 400 and 500 °C, and their electrochemical studies have been carried out. The thin films have been optically and electrochemically characterized by means of transmittance, cyclic voltammetry and chronoamperometry. The mechanism of reduction and oxidation reactions that took place during the potential cycling is presented. The samples deposited at 500 °C exhibit better performance in terms of coloration efficiency, reversibility, contrast ratio and response time.

A time-of-flight mass spectrometric study of laser fluence dependencies in SnO 2 ablation: implications for pulsed laser deposited tin oxide thin films

We report on a time-of-flight mass spectrometric study of laser fluence dependencies in the 532 nm ablation of SnO 2 targets. At all fluences investigated, SnO and Sn 2O 2 are the primary neutral gas-phase species. The relative yield of neutral tin-containing species increases exponentially up to a fluence of ∼1.9×10 8 W cm −2, and saturates at higher fluences. The yield of metal oxide clusters (primarily Sn 2O 2, Sn 4O 4) increases in the saturated region, while the yield of bare metal species (primarily Sn, Sn 2) decreases. In contrast, the peak kinetic energy of the primary neutral ablated species is insensitive to laser fluence in this range. These results support the hypothesis that the initial Sn:O stoichiometry of amorphous SnO x films grown in vacuum using pulsed laser deposition (PLD) plays an important role in the formation of α-SnO during post-deposition annealing.

Properties of spray deposited tin oxide thin films derived from tri- n-butyltin acetate

The thin films of undoped tin oxide were deposited using organotin compound tri- n-butyltin acetate onto the amorphous glass substrates at 673 K by spray pyrolysis technique. The spraying solution concentration of tri- n-butyltin acetate was varied from 12.5 to 100 mM to deposit thin films of tin oxide and their structural, electrical and optical properties have been studied, which were found to be solution concentration dependent. The thermal decomposition behaviour of the tri- n-butyltin acetate salt was studied using differential thermal analysis and thermal gravimetric analysis techniques. The preferred orientation of the film along (110) plane prevails upto 50 mM concentration, which shifts to (200) plane for higher concentrations. The values of room temperature electrical resistivity, carrier concentration and mobility of charge carrier were improved with rise in solution concentration. The samples deposited at 100 mM concentration exhibit better results than any other studied sample. The possible explanation for this is given in the present investigation.

Influence of the nanostructural characteristics on the gas sensing properties of pulsed laser deposited tin oxide thin films

Tin oxide (SnO 2) thin films doped with ∼2 at.% Pt have been deposited onto alumina substrates by reactive pulsed laser ablation of a pure SnO 2 target in an oxygen atmosphere. At a KrF laser intensity of 5×10 8 W/cm 2 and a substrate deposition temperature ( T d) of 300 °C, the pulsed laser deposition (PLD) of SnO 2 thin films was investigated under various oxygen background pressures ( P(O 2)) ranging from 1 to 200 mTorr. While all the deposited films consist of pure polycrystalline SnO 2 phase, their mean grain size and nanoporosity, as deduced from TEM observations, were found to be highly influenced by P(O 2). Indeed, the size of the nanograins that compose the SnO 2 columns was found to increase from ∼4 nm for P(O 2)≤100 mTorr to about 10 nm for P(O 2)≥150 mTorr. The SnO 2 films deposited under P(O 2)≥100 mTorr are shown to exhibit an open inter-columnar porosity, while those grown under P(O 2)=50 mTorr are characterized by randomly distributed spherical nanopores (∼1 nm). The deposited PLD SnO 2 films were integrated into gas-sensing devices and their sensing performance was evaluated for CO gas concentrations ranging from 10 to 250 ppm in synthetic air. It is pointed out that the gas sensitivity of PLD SnO 2 films, having grain size in the (3–10 nm) range, is predominantly influenced by the porosity of the nanostructure.

Structural and electrical studies on highly conducting spray deposited fluorine and antimony doped SnO 2 thin films from SnCl 2 precursor

Tin oxide thin films doped with fluorine, antimony and both have been prepared by spray pyrolysis from SnCl 2 precursor. The respective deposition temperatures of SnO 2:F, SnO 2:Sb and SnO 2:(F+Sb) are 400 °C, 350 °C and 375 °C. The as-prepared films are polycrystalline with a tetragonal crystal structure. The lattice parameter values are not changed by the addition of dopants. The films are preferentially oriented along the (200) direction. The grain sizes vary between 200 and 650 Å. The films have moderate optical transmission (up to 70% at 800 nm) and the calculated reflectivity in the infra-red region is in the range of 88–95%. The figure of merit (φ) values of SnO 2:F and SnO 2:Sb samples are 2.5×10 −3 (Ω) −1 and 1.4×10 −4 (Ω) −1, respectively. The films are heavily doped, degenerate and exhibit n-type electrical conductivity. The lowest sheet resistance ( R sh) of 5.65 Ω/□ obtained for a SnO 2:F sample, is even lower than the values reported for the spray deposited tin oxide thin films prepared from SnCl 2 precursor. The resistivity (ρ) and mobility (μ) are in the range of 10 −4–10 −3 Ω-cm and 7–17.2 cm 2 V −1 s −1. The electron density lies between 1.3×10 20 and 13.2×10 20 cm −3. A thorough electrical investigation reveals that the film's conductivity depends only on carrier concentration. It is found that ionised impurity scattering is the dominant mechanism, which limits the mobility of the carriers.

High-efficiency, low-drive-voltage, semitransparent stacked organic light-emitting device

We report a semitransparent, two-color, stacked organic light-emitting device (SOLED) with high efficiency, low drive voltage, and minimal color distortion. The SOLED emits light from both device surfaces. The external quantum efficiencies of the green and red stacked elements are 1% and 0.4%, respectively, where only the photons emitted from the substrate surface are collected. The drive voltage for the top stack element is decreased to ∼12 V by using a modified indium tin oxide thin film deposition process. Color distortion and angular dependence of the emission spectra are minimal.

Plasma cathode—surface interaction in reactive magnetron sputtering for indium—tin-oxide thin film deposition

The d.c. magnetron sputtering process of an indium-tin-oxide (ITO) target in Ar/O 2 is studied. Compared with the reactive sputtering of an aluminium target, which is very sensitive to the introduced O 2 pressure and which shows a clear transition between metal sputtering and oxide sputtering modes, the reactive sputtering of an ITO target is insensitive to the preset pressure of introduced O 2 in respect to the current-voltage characteristic. Experimental results of laser induced fluorescence measurement of sputtered indium atoms, optical emission measurement of neutral atoms in excited states, electrical measurement of discharge current-voltage characteristic, and measurement of deposited film properties (transmittance, resistivity and deposition rate) are presented. Effects of the preset pressure of introduced O 2 on these parameters are investigated under a wide variety of preset pressure ranges. The change of the sputtering process is mainly governed by a change in the surface condition of the target. An inherent supply of O 2 from the ITO target into the plasma during sputtering is an important key to understanding the reactive sputtering process of ITO target.

Comparison of properties of tin oxide films deposited by reactive-partially ionized beam, ion assisted, and hybrid ion beam methods

Abstract A hybrid ion beam (HIB) technique that consists of a reactive-partially ionized beam deposition (R-PIBD) and a gas ion gun was adopted to deposit tin oxide thin films on Si (100) substrate under various deposition conditions. Tin oxide films grown by R-PIBD showed nonstoichiometric composition and the main phases of the films consisted of Sn metal and SnO. Surface roughness of the films deposited by R-PIBD were changed from 4.7 to 27.4 nm with increasing acceleration voltage from 0 to 4 kV. The films assisted by oxygen ion show the chemical state of Sn4+ which is similar to that of a standard SnO2 powder. Also, the films represent flat surface roughness much less than the case of R-PIBD. A film with a highly preferred orientation along the SnO2 (200) plane and with grain size 80.5 nm was successfully grown by IAD. The SnOx films composed of grains with nanosize are discussed in terms of chemical state, composition ratio, crystallinity, and surface roughness.

XRD and SEM studies of reactively deposited tin oxide thin films

Stoichiometric polycrystalline tin oxide thin films were deposited by the reactive evaporation of tin and the SnO2 formation was found to be strongly dependent on the deposition parameters. The preferred orientation of the SnO2 films deposited on different substrates was varying due to the dislocation defects arising during the thin film formation. The X-ray diffraction (XRD) studies identified a tetragonal structure while the scanning electron microscopic (SEM) studies revealed a polycrystalline surface for the SnO2 films reactively deposited.

Copper-doping level effect on sensitivity and selectivity of tin oxide thin-film gas sensor

The influence of doping level of basic material on electrical resistance controlled by gas chemisorption is investigated experimentally for chemically deposited tin oxide thin films with different amounts of Cu and Sb additives. Significant modification of dependences of resistance versus temperature in oxygen-rich atmosphere and anomalous change of selectivity of resistance response to CO and H 2 gas are obtained by different doping levels of the films. The main features of the experimental results are explained by the variation of the position of the Fermi level with the concentration of bulk impurities.