SnO2 Thin Films Research Articles

Experimental Investigation and DFT Study of Tin-Oxide for Its Application as Light Absorber Layer in Optoelectronic Devices

Experimental investigation of SnO film has been performed to analyse the effect of oxygen ratio variation on its optical and electrical properties. The oxygen composition in SnO film has been varied and correspondingly its extinction coefficient and band gap have been obtained. Also, density functional theory (DFT) study of SnO film has been carried out in order to obtain its optical properties such as extinction coefficient and corresponding bandgap. The experimental and theoretical trends related to its optical properties are in good agreement with each other. The SnO film may be used as a prospective light absorber layer in various opto-electronic sensor devices, solar cell in particular, and its optoelectronic properties can be tuned with change in oxygen mole fraction ratio of SnO films which are detailed out in this paper. Further, some important electrical parameters of such as Hall mobility, carrier concentration and resistivity of SnO films for its different Sn and O ratios have been obtained. The investigation of tunable optical and electrical properties of SnO thin film will pave the way for a wide range of opto-electronic devices.

Multi-pulse atomic layer deposition of p-type SnO thin films: growth processes and the effect on TFT performance

P-type SnO thin films have been deposited using multiple pulses of a novel Sn(ii) precursor per ALD cycle. The study looks at the effect on TFT performance and AFM analysis has explored the change in the growth processes during deposition.

Synthesis and characterization of thermally evaporated Er-doped SnO2 thin films for photonic applications

In this study, different compositions of transparent films of erbium-doped tin oxide were created utilizing the thermal evaporation process on glass substrates. The tetragonal phase is verified by XRD analysis. The visible spectrum's strong transmittance was seen in the films. The films' transmission spectra ranged from 75 to 85% transmittance in the visible range with varying Er concentrations. Using Tauc's relation, values of the optical direct band gap have been calculated. The rutile phase of tin oxide is indicated by the Raman scattering peaks. PL measurements show thatonly the emission-related on a peak at 656 nm of Er3+ ions due to transition from 4I15/2 to 4F9/2 level and with the presence of doping, this emission becomes more intense. From the AFM measurements, the RMS roughness and grain size of films were computed. The results obtained show that these samples have wide applications in optoelectronic devices.

Effect of deposition parameters on optical and electrical properties of ZnO–In2O3–SnO2 thin films

A combinatorial study was carried out using a magnetron sputtering system to determine suitable ternary compositions of ZnO–In2O3–SnO2 (ZITO) thin films for optoelectronic applications. Samples were obtained on glass substrates via the co-sputtering of high purity oxide targets. Parameters such as the sputtering gas pressure, deposition time and substrate temperature were studied as the process variables and their effects on the composition, optical, and electrical properties of the thin films were examined in detail. The results have revealed that the samples deposited under a sputtering gas pressure of 10 mTorr and deposition time of 45 min in the Zn-rich region presented the best optical properties (max. 84%), whereas In-rich compositions exhibited better electrical properties (min. 14 Ω/□). More specifically, 61.7 at.% Zn, 31.4 at.% In, and 6.9 at.% Sn was determined as the most suitable ZITO composition for various optoelectronic applications. In addition, the increase in deposition temperature enhanced the optoelectronic properties of the thin film samples as well as their crystal quality.

Enhanced infrared transmittance by modulation of electrical and optical properties of Sm-doped SnO2 thin films

Although metal oxides exhibit high electrical conductivity and high transparency in the visible wavelength range, they suffer from low transmittance in the infrared (IR) spectral range. This paper reports the deposition of Sm-doped SnO2 thin films with high IR transparency by modulating the electrical and optical properties. The Sm-doped SnO2 thin films grown by spray pyrolysis showed a directional columnar structure and a change in crystal structure from tetragonal to orthorhombic with increasing Sm doping content. The undoped SnO2 thin film exhibited intrinsic n-type conductivity with a high background charge carrier concentration, which resulted in low IR transmittance of <20%. As the Sm doping content increased, the charge carrier concentration decreased drastically, resulting in an increase in IR transmittance of SnO2 thin films from 18.8 to 85.2%. The Sm element acted a critical role in controlling the electrical and optical properties of SnO2 thin films by acting as a reducing agent and dopant.

Influence of Ru doping on the structural, morphological, optical, electrical and optoelectronic properties of SnO2 thin films

Tin oxide (SnO2) and various concentrations (1, 2, 3 and 4 wt%) of ruthenium (Ru)-doped tin oxide (SnO2:Ru) films were deposited on microscope glass slides using an economical laboratory-made spray pyrolysis method. The influence of Ru doping on the physical properties of SnO2 films was studied using X-ray diffraction (XRD), UV–visible–near-infrared spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, photoluminescence (PL), micro-Raman spectroscopy and Hall measurement analyses. The XRD result corroborates that all the prepared films belong to tetragonal crystal structure with P42/mnm space group and reveals that crystallite size decreases from 29.06 to 22.41 nm. The 3 wt% Ru-doped SnO2 film has a high average optical transmittance (88%) in the range of 400–1100 nm. The calculated optical band gap ranges within 3.50–3.76 eV. The SEM micrographs reveal the morphology changes and grain size decrement as a function of Ru doping. Metal oxide vibration (O–Sn–O) is confirmed using FT-IR and micro-Raman spectral analyses. The PL spectra measured at room temperature exhibit a strong blue emission at 420 nm for all films. All prepared thin films show resistivity of the order of 10−3 Ω cm. The highest figure of merit of 2.627 × 10−4 Ω−1 is obtained for 3 wt% of Ru doping in the wavelength range of 400–1100 nm. The present investigation clearly shows that the structural, optical, morphological, electrical and optoelectronic properties of SnO2 thin films are effectively modified by the Ru dopant. Particularly, the 3 wt% of Ru-doped SnO2 films could be useful for the electron transport layer in solar cells and other optoelectronic applications.

Effects of Substrate Temperature on Properties of Sb-doped SnO2 Thin Film

Effects of Substrate Temperature on Properties of Sb-doped SnO2 Thin Film

Spray Pyrolyzed Praseodymium Doped SnO2 Thin Film with Fast Response to LPG: Analysis Based on Microstructural Features

Praseodymium (Pr) doped (0.1 to 6 wt. %) nanostructured SnO2 thin films are prepared via nebulizer assisted spray deposition process at a deposition temperature of 320 °C. The analyses show that the films grow in (110), (301) and (310) preferred orientations. The fabricated sensing films are exposed to LPG at 500 ppm concentration and at different operating temperatures. In 500 ppm of LPG, at an operating temperature of 350 °C, a commendable sensor response of 99 % with fast response time of 9 s and recovery time of 11 s is shown by 1wt.% Pr doped film, which is appreciable compared to pristine SnO2 film. The sensor response reduces at lower operating temperatures. Microstructural investigations justify the gas sensing performance of 1 wt.% Pr doped SnO2 thin film. Raman and photoluminescence studies give an insight into oxygen vacancies and trapped states that have a crucial influence on gas sensing.

The influence of different complexing agents on the properties of tin dioxide (SnO2) deposited thin films through chemical bath approach

The present study explores the effect of disodium ethylenediamine tetraacetic acid and triethanolamine as alternative complexing agents to synthesize SnO2 thin films by employing simplistic chemical bath deposition method. The as-deposited tin dioxide thin films have been characterized by various analytical techniques particularly X-rays diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive x-ray analysis (EDX), and Raman spectroscopy. The XRD and Raman spectroscopy reveal the crystalline nature pertaining small crystal grains of the as-deposited SnO2 thin films with a tetragonal rutile structure. The SEM analysis unfolds that as-synthesized thin films using disodium ethylenediamine tetraacetic acid and triethanolamine, the grains of the films exhibit different shapes. The bandgap energies of the films have been estimated from the absorbance spectra through Tauc plot and the respective optical band gap of SnO2-EDTA and SnO2 -TEA exhibits the values as ∼4.2 eV and ∼3.8 eV, respectively. These findings suggest as-deposited tin dioxide thin films to be pertinent for use in solar radiation absorption applications.

Nonlinear optical properties of cobalt doped SnO2 thin films

In this study, the nonlinear optical properties of (0–5 at% Co/Sn) doped tin oxide thin films is investigated. The linear spectroscopy using UV-Vis spectrometry in the spectral range 300–900 nm reveals that the films have a direct band gap energy between 3.74 and 3.79 eV, and Urbach energy in 0.64 – 1.1 eV range. The non-linear refractive index and the associated third order nonlinear susceptibility χ(3)(ω) are estimated from self-Kerr effect. The dependence with respect to the photon energy have been drawn for all samples, as results it is shown that all samples have strong nonlinear susceptibilities in the near of ultraviolet range.

Detection of ammonia gas at room temperature through Sb doped SnO2 thin films: Improvement in sensing performance of SnO2

This paper presents the effects of Sb doping on the gas-sensing properties of SnO2 thin films prepared through a nebulizer-assisted spray pyrolysis technique. An improvement in the inherent characteristics of the transparent conducting oxide after 0 to 5 wt% Sb doping is reported. The deposited films were used to sense the presence of 50 to 250 ppm of ammonia at room temperature. Various analytical techniques were used to analyze the properties of the Sb-doped SnO2 films. X-ray diffraction spectra revealed the tetragonal structure of crystallites, and the maximum crystallite size was observed in the 2-wt%-Sb-doped SnO2 film. The morphological images showed spherical grains in pristine SnO2 films and their transformation to a trigonal shape after Sb doping; particularly, a large grain size was observed at 2 wt% doping. PL studies of the materials revealed that a large number of oxygen vacancies exist in the 2-wt%-Sb-doped SnO2 thin film. The transmittance of the films remained at approximately 75%, and the band gap varied from 3.94 to 4.01 eV as the doping concentration varied from 1 to 5%. A high response of 138% was observed for 250 ppm of ammonia in the case of the 2-wt%-Sb-doped SnO2 film, with a 42 s response time and a 11 s recovery time. Thus, the 2-wt%-Sb-doped SnO2 thin film has suitable characteristics for application as an efficient gas sensor to detect ammonia.

High-κ SrTiO3 thin film as gate dielectric of a solution processed SnO2 thin film transistor

High dielectric constant (high-κ) gate insulating material is an essential component for low operating voltage thin film transistor (TFT) fabrication. Among different high-κ materials, a number of perovskite oxides are widely studied due to their unusually high dielectric constant. Out of them, strontium titanate (SrTiO3) is a well-known perovskite oxide material that has both good insulating behaviors with a very high-κ value. This work demonstrated the SrTiO3 thin film deposition by simple solution processed technique and its application for sol-gel derived SnO2 TFT fabrication. Although this SnO2 TFT can be operated within a low voltage range (<2 V) due to the high-κ value of SrTiO3 thin film, the device can be operating in the high voltage range (>15 V) as well because of its high breakdown voltage. Experimental data of this study indicates, in the low voltage range (<2 V), both output and transfer characteristics of the devices are hysteresis free. However, in the higher voltage range (>5 V), TFT characteristics show some hysteresis. An optimized TFT has carrier mobility ∼0.20 cm2/V.s. with an On/Off ratio of 2.3 × 104 in the low operating voltage range (<2 V) range. Whereas, carrier mobility is reduced a bit in the higher voltage range with a lower On/Off ratio due to the interface charge trapping.

Structural, morphological, optical and electrical properties of Ni-doped SnO2 thin films by pneumatic spray pyrolysis method

Structural, morphological, optical and electrical properties of Ni-doped SnO2 thin films by pneumatic spray pyrolysis method

Black phosphorus nanodot incorporated tin oxide hollow-spherical heterojunction for enhanced properties of room-temperature gas sensors

The marriage of traditional gas-sensing semiconductors with low dimensional nanostructures is expected to exhibit interesting properties in the detection of hazardous gases. Herein, novel hollow-spherical heterojunctions are assembled for thin film gas sensors by using p-type black phosphorus (BP) and n-type tin oxide (SnO2). Green synthesis strategies are employed to prepare BP nanodots and SnO2 quantum dots. The aerosol-assisted chemical vapor deposition is used to prepare thin films with hollow-spherical heterojunctions. The BP incorporation significantly improves the gas-sensing properties of SnO2-based thin films, which demonstrate excellent response and repeatability to H2S at room temperature. The BP-SnO2 heterojunction demonstrates more than twice the response and sensitivity of pristine SnO2 thin film. Moreover, the recovery ability is significantly improved and LOD is decreased to 50 ppb. The hollow-spherical heterojunction has a joint gas-sensing mechanism contributed by both of SnO2 and BP. The SnO2 provides fundamental receptor function for gas detection while incorporated BP facilitates the adsorption of target H2S and provides additional electrons through the p-n junction tunnel. In addition, a slight negative dependence on humidity is observed for the gas sensor. It is ascribed to the competitive adsorption of water molecules on the BP-SnO2 heterojunction surface against H2S molecules and chemisorbed oxygen. This work not only proposes novel heterojunction nanostructures for room-temperature gas detection, but also contributes to the functional integration of traditional gas-sensitive materials and emerging 2D materials in sensor technology.

Influence of multi-layer TiO2/SnO2 heterojunctions on fast and sensitive ethanol detection

The fabrication of MEMS gas sensors based on SMO sensing materials has become popular in commercials. However, due to the dense surface, the MEMS gas sensor based on sputtered sensing film always shows low sensitivity and slow response. Herein, we report multi-layer TiO2/SnO2 heterojunctions sensing film deposited by sputtering techniques. SnO2 and TiO2 thin film have an approximate thickness of 265.34 nm and 66.28 nm, respectively. The effects of different-layer TiO2/SnO2 heterojunctions and annealing temperatures to sensing film on gas sensing properties were investigated. The different samples with the same surface and annealed temperature exhibit different gas sensing properties, which indicates that more layer heterojunctions may decrease the positive effects of heterojunctions and oxygen adsorptions on the gas sensing properties. The two-layer TiO2/SnO2 heterojunctions sensing film with an annealed temperature of 400 °C in air obtain the best gas sensing properties, which has a response value of 7.54 and response/recovery time of 33/298 s to 50 ppm ethanol at 260 °C. Furthermore, the MEMS gas sensor based on two-layer TiO2/SnO2 heterojunctions sensing film can detect ethanol ranging from 1 ppm to 1000 ppm with excellent linearity.

Morphological and structural study on low cost SnO2 counter electrode and its applications in quantum dot sensitized solar cells with polysulfide electrolyte

Fabrication of efficient CdS quantum dot sensitized solar cell with a novel stable counter electrode based on a thin film of SnO2 is revealed. The film was characterized by using Scanning Electron Microscopy (SEM), High-Resolution Tunneling Microscopy, X-ray diffraction (XRD) and UV–Visible spectroscopic techniques. Photovoltaic performances and Electrochemical Impedance Spectroscopic techniques (EIS) were performed on FTO/TiO2/CdS/polysulfide/SnO2/FTO device under the light illumination of 100 mW cm−2 and comparison was done with the conventional Pt counter electrode. Impressive 43 % efficiency enhancement in these solar cells was achieved compared with the Pt based devices. Porous thick nanostructure of SnO2 with crystal defects such as oxygen vacancies and Sn vacancies arising from lattice structures as confirmed by SEM, Raman and, XRD spectroscopy could be some of the reasons for this enhancement. Excellent photo enhanced electrocatalytic activity against the polysulfide electrolyte is confirmed by EIS and Cyclic Voltammetry studies.

Synthesis of Co, Fe co-doped SnO2: characterization and applications

Thin films of iron and cobalt co-doped tin oxide were deposited by spray pyrolysis technique on heated glass at 480°C with moving nozzle method. The weight ratio of Fe/Co co-doped SnO2 (Fe CTO) changed in the range of 4-16 wt.%. The structural, optical and biological characteristics were carried out by using different characterization techniques, Results from XRD, SEM, EDX and UV-Vis analyses demonstrated successful synthesis shows polycrystalline structures with cassiterite tetragonal crystal phase with a preferential orientation for co-doped SnO2 toward (211), The average grain size of the thin films was found to be 39.29 nm, SEM images showed that all sample having uniform morphology with variant shape upon increasing dopant concentration, Transmittance spectra of all the thin films display high transparency more than 80% in the visible region, and band gap (Eg) varies from 3.49 to 3.75 eV. Antibacterial activity of the doped SnO2 thin films is studied were investigated by agar method as showed good activity against both Gramnegative Escherichia coli (E.coli) and Gram-positive bacteria Staphylococcus aureus (S.aureus).confirming these as future broad-spectrum antibacterial. Thus the preparation is a good candidate for further development into therapeutic formulations.

Al3+ doping induced changes of structural, morphology, photoluminescence, optical and electrical properties of SnO2 thin films as alternative TCO for optoelectronic applications

Highly transparent and conductive pure (SnO2) and aluminum doped tin oxide (Al:SnO2) thin films were deposited on glass substrates by the sol-gel spin-coating method. The structural, morphological, optical and electrical properties of the prepared thin films at different doping rates have been studied. X-ray diffraction results revealed that all the films were polycrystalline in nature with a tetragonal rutile structure. SEM images of the analyzed films showed a homogeneous surface morphology, composed of nanocrystalline grains. The EDS results confirmed the presence of Sn and O elements in pure SnO2 and Sn, O, Al in doped SnO2 thin films. The optical results revealed a high transmittance greater than 85% in the visible and near infrared and a band gap varying between 3.82 and 3.89 eV. PL spectra at room temperature showed that the most dominant defects correspond to oxygen vacancies. A low resistivity of order varying between 10−3 and 10−4 Ω cm and a high figure of merits ranging between 10−3 and 10−2 Ω−1 in the visible range were obtained. The best performances were obtained for samples containing 2 at. % Al, which could be used as an alternative TCO layer for future optoelectronic devices.

Nanostructuring of SnO2 Thin Films by Associating Glancing Angle Deposition and Sputtering Pressure for Gas Sensing Applications

SnO2 thin films were prepared by conventional and Glancing Angle Deposition reactive sputtering, and their gas sensing properties were investigated. The porosity of the as-prepared films was widely assessed using optical methods, and the sensing performances of these active layers were correlated with the evolution of surface and film porosity as a function of deposition conditions and annealing treatment. The sensor made of inclined columns grown at high sputtering pressure (6 × 10−3 mbar) and annealed at 500 °C in air exhibited the best response to benzene, with a limit of detection of 30 ppb. In addition, successful BTEX (i.e., benzene, toluene, ethylbenzene, and xylenes) discrimination was achieved by combining the sensing signals of four nanostructured tin-oxide-based gas sensors.

High-performance Atomic-Layer-Deposited SnO thin film transistors fabricated by intense pulsed light annealing

In this study, SnO films were grown by atomic layer deposition using Sn(dmamp)2 and H2O as the Sn-precursor and reactant, respectively, at a low temperature of 120 °C. Intense pulsed light (IPL) annealing was employed to obtain high-quality polycrystalline SnO films with excellent hole transport characteristics. The amorphous SnO film could be crystallized by IPL annealing, particularly at a light pulse number between 200 and 300, and the degree of crystallinity increased with increasing IPL treatment. The Sn2+ oxidation state of the SnO film was almost maintained after IPL annealing, with no apparent phase transformation from SnO to SnO2 or Sn. In addition, the IPL-annealed SnO films exhibited a smooth surface morphology with a root-mean-squared roughness of 0.22–0.50 nm. Finally, bottom-gated staggered-structured thin-film transistors (TFTs) were fabricated with 6–30 nm-thick IPL-annealed SnO channel layers. Excellent p-type SnO-based TFT performance was achieved with a field-effect hole mobility of 4.31 cm2/V·s and an on-to-off current ratio of 8.2 × 104.