SnO2 Thin Films Research Articles

Impact of Ta doping on the optoelectronic and catalytic properties of SnO2 thin films

Impact of Ta doping on the optoelectronic and catalytic properties of SnO2 thin films

Enhancements of Structural and Optical Properties of MgO: SnO2 Nanostructure Films

This study investigates the structural and optical properties of MgO:SnO2 nanoparticles using the Chemical precipitation method, The thin films were deposited by the spin coating technique on glass substrates. X-ray diffraction analysis proved the crystalline structure of prepared thin films, with the peaks corresponding to the (110), (101), (200), (211), and (220) planes, with the tetragonal SnO2 crystal structure, Fourier transforms infrared (FTIR), and scanning electron microscope (SEM) used to characterize the functional groups, shape, and dimensions of synthesized metal oxide nanoparticles. The optical properties of the films were studied by UV-Vis spectroscopy, and the bandgap energy was estimated to be in the range of (3.9 - 3.4 eV). The refractive index and extinction coefficient of the films were also determined, and the results indicated that the films had good transparency in the visible region, The study concludes that MgO:SnO2 thin films obtained by spin coating technique have potential applications in optoelectronics and gas sensors.

Aluminium Doped Tin Oxide (ATO) Thin Films Grown onto Glass Substrate by Spray Pyrolysis Technique

Nanostructured Al doped Tin Oxide (ATO) thin films were deposited on cleaned glass substrate by spray pyrolysis technique at 400 °C using a solution consisting of SnCl4 starting as material and doping source AlCl3 which were dissolved in methanol and stirred four hours. The effect of changes in doping source content of Al:SnO2 thin films were investigated and studied the crystalline structure, surface morphology, transmittance and optical band gap of ATO films. The dopant concentration varied from 0 to 10%. X ray diffraction studies conformed the proper phase formation in the films are polycrystalline without any second phase with preferential orientations along the (110), (200), and (211) planes and an average grain size of 20 nm. The visible transmittance exceeds 85% and the optical band gap was estimated to be around 2.6 eV to 3.6 eV. The scanning electron microscopic (SEM) studies showed the particle size lying in the range 20 nm for undoped films and it is decreasing while increasing of Al doping.

Controlled orientation and microstructure of p-type SnO thin film transistors with high-k dielectric for improved performance

Despite its relatively high hole mobility, the electrical performance of p-type SnO thin-film transistors (TFTs) lags behind that of n-type oxide TFTs. In this study, we present an approach to enhance the performance of p-type SnO TFTs by utilizing an atomic-layer-deposited SnO/high-k structure, with crystalline HfO2 (c-HfO2) serving as a high-k dielectric. However, the grain boundaries on the c-HfO2 surface influenced the microstructure and orientation of the SnO layer, resulting in a random orientation and surface roughening. To address this issue, we modified the c-HfO2 surface with an amorphous ultrathin Al2O3 layer to eliminate the grain boundaries on the deposition surface. This enabled the alignment of the (00l) SnO planes parallel to the substrate surface and provided a smooth surface. Moreover, the introduction of ultrathin Al2O3 into SnO/high-k stacks substantially improved the electrical performance of p-type SnO TFTs. Our findings highlight the potential of integrating van der Waals semiconductors with high-k dielectrics, facilitating opportunities for advanced device applications.

Drop-Dry Deposition of SnO2 Using a Complexing Agent and Fabrication of Heterojunctions with Co3O4.

The drop-dry deposition (DDD) is a simple chemical technique of thin film deposition, which can be applied to metal oxides. The deposition solution is an aqueous solution including a metal salt and an alkali. However, some metal ions react spontaneously with water and precipitate. This work is the first attempt to use complexing agents in DDD to suppress the precipitation. SnO2 thin films are fabricated using DDD with Na2S2O3 as a complexing agent and via annealing in air. The results of the Auger electron spectroscopy measurement show that the O/Sn composition ratio of the annealed films approached two, indicating that the annealed films are SnO2. The photoelectrochemical measurement results show that the annealed films are n-type. Co3O4/SnO2 heterojunction is fabricated using p-type Co3O4 films which are also deposited via DDD. The heterojunction has rectification and photovoltaic properties. Thus, for the first time, a metal oxide thin film was successfully prepared via DDD using a complexing agent, and oxide thin film solar cells are successfully prepared using only DDD.

Atomic layer deposited SnO2/ZnO composite thin film sensors with enhanced hydrogen sensing performance

Hydrogen gas (H2) has long been regarded as a clean and renewable energy carrier alternative to the fossil fuel, therefore the development of highly sensitive and reliable hydrogen sensor is imperative for the large-scale implementation of green energy hydrogen. In this work, SnO2, ZnO thin film and SnO2/ZnO composite thin film H2 sensors were fabricated on SiO2/Si substrates by atomic layer deposition (ALD). The effect of ALD cycles and heat treatment temperatures on the sensing properties of the thin film sensors was investigated deeply. It is found that the 100-cycle SnO2/150-cycle ZnO composite film shows the best H2-sensing performance such as large response of 93 to 30 ppm H2 at 200 ℃, fast response/recovery time of 50 s/29 s, and low detection limit of 250 ppb. Moreover, the response of SnO2/ZnO composite film sensor is 10 times and 2 times higher than that of the pure ZnO and SnO2 thin film ones at working temperature of 200℃, respectively. A possible mechanism for performance improvement of the SnO2/ZnO composite film H2 sensor is proposed, attributed to the synergistic effect of the SnO2-ZnO heterojunction and the oxygen vacancies in the SnO2 film. ALD may be a feasible strategy to construct Si-based highly sensitive hydrogen sensors for micro-electromechanical system application.

Structural, optical, and dielectric characteristics of pulsed laser deposited SnO2-TiO2 composite thin films

Pulsed laser deposition was used to fabricate the thin films of SnO2 and SnO2-TiO2 composites on FTO substrates and these films were characterized to understand the effect of TiO2 on the structural, optical, and electrical properties of SnO2. The Tauc plots confirm that the composite films have a higher band gap energy than SnO2. EDX spectra demonstrate that the thin films contain Ti, Sn, and O ions. The photoluminescence (PL) spectra indicate three blue emission bands at wavelengths of 410, 435, and 460 nm and these are due to the oxygen vacancies or interstitial oxygen ions and defect-related states. These films are n-type semiconductors as verified by the Hall Effect measurements. At the interface of the film, the frequency dependence of the dielectric at room temperature reveals that as the frequency increases, the dielectric constant and dielectric losses decrease. SnO2 film has a significantly higher a.c. conductivity than the SnO2-TiO2 composite films. The correlated barrier hopping (CBH) mechanism is responsible for the conduction behaviour and obeys Johncher’s power law (n < 1). The addition of TiO2 in SnO2 affects the structural, optical, dielectric, and ac conductivity of films at room temperature.

Highly Sensitive and Selective Hydrogen Gas Sensor with Humidity Tolerance Using Pd-Capped SnO2 Thin Films of Various Thicknesses

Detecting and identifying hydrogen gas leakage before a potential disaster is a critical safety concern. To address this issue, a low-cost and simple-design sensor is required with high response and fast sensing time, capable of detecting hydrogen gas even at low concentrations of 5–500 ppm. This study investigates the use of magnetron-sputtered SnO2 thin films with palladium as a catalytic layer to achieve better sensing output. The developed Pd-caped SnO2 thin film sensors showed increased sensitivity with increasing thickness, up to 246.1 nm at an operating temperature of 250 °C. The sensor with a thickness of 246.1 nm exhibited excellent selectivity for H2 gas, even in humid conditions, and was able to distinguish it from other gases such as CO, NH3, and NO2. The sensor demonstrated high response (99%) with a response/recovery time of 58 s/35 s for (5–500 ppm) hydrogen gas. The sensor showed linear response to H2 gas concentration variation (5–500 ppm) at 250 °C. The sensor was found to be mechanically stable even after 60 days in a high-humidity environment. The LOD of sensor was 151.6 ppb, making it a suitable candidate for applied sensing applications. The Pd-caped SnO2 thin film sensor with thickness of ~245 nm could potentially improve the safety of hydrogen gas handling.

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.

UV-activated SnO2 thin film for air-atmospheric oxygen sensing at room temperature

UV-activated SnO2 thin film for air-atmospheric oxygen sensing at room temperature

Self-Powered Mechanical Energy Sensor Application of SnO2/Ag and PMMA/ITO Nanocomposites via Triboelectric Effect

The triboelectric nanogenerator is a state-of-the-art device for addressing the growing problem of meeting the world's ever-increasing energy needs by converting mechanical energy into electrical energy. Using the popular semiconductor SnO2 nanostructured thin films as a triboelectric layer over contact regions, as opposed to polymers with lesser performance, increases the output power and life time of nanogenerators. In order to design a triboelectric nanogenerator, deposited thin film SnO2 is used as a friction layer with Ag electrode after heat-treatment at 623 K with a contrary layer of PMMA poly (methyl-methacrylate) with ITO electrode. The structural and electrical properties were analyzed by using scanning electron microscopy (SEM), electro-impedance spectroscopy (EIS) and atomic force microscopy (AFM) measurements. The increased output power of the triboelectric nanogenerator is attributed to the nanoscale PMMA contact charge created by tunneling electrons in the SnO2/Ag nanocomposite thin film layer. Due to its proximity to the PMMA/ITO surface, the SnO2/Ag layer causes electron field emission, and tapping the SnO2/Ag layer may result in electron cloud overlap. Similar to a semiconductor/insulator interface, the Fermi level of SnO2 plays a crucial role in electron transport. The system efficiency stated as a touch detector in a conventional keyboard that generates its own power is revealed in part by an analysis of its operating state up to the 4V.

Effect of (Al, Zn, Cu, and Sr) doping on structural, optical and electrical properties of sprayed SnO2 thin films

Tin dioxide thin films deposited onto a glass substrate were prepared by spray pyrolysis technique, and then doped with different elements which are: Al, Zn, Cu, and Sr by electroplating method, these elements were chosen for their different atomic radii. XRD illustrate that all the films were polycrystalline with a tetragonal rutile structure and a strong preferred orientation of (200) plane. Uv-vis spectrophotometer specters showed that the highest average transmittance of Al/SnO2 film was about 86.77% in the visible region and the Sr/SnO2 film had the highest band gap of 3.95 eV. From the MEB images, the morphological characteristics improved when the SnO2 thin films doped with Al and Zn but the opposite happened when it doped with Cu and Sr. The four-point probe showed that the best sample was for Al/SnO2 because it had the highest electrical conductivity around 692.306 (Ω.cm) -1.

Flexural Strength and Vickers Microhardness of Graphene-Doped SnO2 Thin-Film-Coated Polymethylmethacrylate after Thermocycling

Removable dental prostheses are commonly fabricated using polymethylmethacrylate, a material that does not have favorable mechanical properties and needs reinforcement with particles such as graphene. The aim of this study was to evaluate the flexural strength (FS) and Vickers microhardness of a heat-polymerized polymethylmethacrylate coated with graphene-doped stannic oxide (SnO2) thin films using a thermionic vacuum arc method after thermocycling. Forty bar-shaped specimens (65 × 10 × 3 mm) were fabricated using a heat-polymerized denture base resin and divided into four groups according to the graphene-doped SnO2 thin film surface coating performed: No-coat (uncoated), Coat-15 s (coating duration of 15 s), Coat-20 s (coating duration of 20 s), and Coat-30 s (coating duration of 30 s) (n = 10). The thermionic vacuum arc method was used to coat both surfaces of the specimens of each test group with varying durations, and surface coating was verified using Fourier Transform Infrared Spectroscopy. Specimens were subjected to 10,000 cycles of thermocycling. Atomic force microscopy was used to evaluate the surfaces of all specimens before and after thermocycling. Microhardness values were measured five times and averaged. Then, each specimen was subjected to a three-point bending test, and FS values were calculated. Data were analyzed using one-way analysis of variance and Bonferroni tests (α = 0.05). Differences among test groups were nonsignificant when FS data were considered (p = 0.605). However, significant differences were observed among test groups when Vickers microhardness data were considered (p &lt; 0.001). Coat-30 s had the highest hardness (p ≤ 0.003), while the difference among remaining groups were nonsignificant (p ≥ 0.166). Graphene-doped SnO2 thin film surface coatings did not significantly affect the FS of tested heat-polymerized denture base resin but increased the Vickers microhardness when the coating duration was 30 s.

Sub-500 nm patterned synthesis of corrosion resistant SnO2 and Pt@SnO2 using metal-organic precursor

In this study, a thin film of transparent conducting metal oxide, SnO2, is obtained using a novel metal-organic precursor, Sn-TOABr complex. The precursor is synthesized by phase-transferring tin from the aqueous layer to the liquid-liquid interface. The formed precursor is used for depositing SnO2 thin films over arbitrary and even large substrates via the modified atmospheric pressure chemical vapor deposition (MAPCVD) method in a simple furnace at 450 °C. The vapor-deposited SnO2 thin films are crystalline, semiconducting, highly transparent with excellent mechanical robustness against scratch and scotch tape tests, and resistant towards corrosive media. The obtained robust thin films via this MAPCVD technology expand applications towards protective coatings for arbitrary substrates. Using a simple direct micromolding technique, sub-500 nm patterns of SnO2 and Pt@SnO2 were obtained. This single-step soft lithography patterning technique, besides being cost-effective, offers a large throughput.

Physical Properties of SnO2/WO3 Bilayers Prepared by Reactive DC Sputtering

The combination of transparent and conductive SnO2 with colored WO3 thin films has interesting uses in electrochromic windows, photovoltaic cells and photocatalytic systems, where the SnO2/WO3 bilayer can improve the device efficiency by increasing the charge separation and extending the energy range of photoexcitation. In this work, SnO2 and WO3 thin films were prepared by reactive DC sputtering from Sn and W targets, respectively. Single layers and bilayers deposited on glass substrates have been analyzed by X-ray diffraction, atomic force microscopy, spectrophotometry, and electrical measurements. SnO2 crystallizes in the cassiterite structure, whereas amorphous WO3 is obtained on bare and SnO2-coated glasses, showing higher surface roughness on the SnO2 layer. Different oxygen vacancy defects have been identified in WO3 by analyzing photoconductivity transients. The oxygen vacancy defects are responsible for the sub-bandgap absorption that causes coloration in the WO3 films. Regarding SnO2, it shows a high transmittance of about 90% in the visible and near-infrared spectral ranges.

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

Transparent and conductive thin films of cadmium doped tin oxide fabricated by pulsed laser deposition technique

Transparent conducting thin films of cadmium doped tin oxide (CTO) were successfully fabricated on glass substrates by pulsed laser deposition technique. Several analytical tools were employed to explore the causes of changes in the structural, optical and electrical properties of these films as a function of doping concentration. The 3 wt % Cd doped films showed lowest electrical sheet resistance of 300.9Ω/□ with electrical resistivity of 2.407×10−3Ωcm. The CTO films are optically transparent with more than 80% transmission in the visible and near IR region of the electromagnetic spectrum. The optical energy gap of CTO films marginally varied from 3.40 eV to 3.49 eV for different doping amount. The AFM studies showed an increase in the surface smoothness of the film with Cd doping concentration. The X-ray diffraction study revealed the tetragonal structure of the film with lattice parameters a=4.742Å and c=3.177Å. The enhanced electrical conductivity and optical transmittance characteristics in these pulsed laser deposited Cd:SnO2 thin films, are suitable, for photo anode/electrode applications in solar cells and display panels.

Moderate temperature deposition of RF magnetron sputtered SnO2-based electron transporting layer for triple cation perovskite solar cells

The perovskite solar cells (PSCs) are still facing the two main challenges of stability and scalability to meet the requirements for their potential commercialization. Therefore, developing a uniform, efficient, high quality and cost-effective electron transport layer (ETL) thin film to achieve a stable PSC is one of the key factors to address these main issues. Magnetron sputtering deposition has been widely used for its high quality thin film deposition as well as its ability to deposit films uniformly on large area at the industrial scale. In this work, we report on the composition, structural, chemical state, and electronic properties of moderate temperature radio frequency (RF) sputtered SnO2. Ar and O2 are employed as plasma-sputtering and reactive gases, respectively. We demonstrate the possibility to grow a high quality and stable SnO2 thin films with high transport properties by reactive RF magnetron sputtering. Our findings show that PSC devices based on the sputtered SnO2 ETL have reached a power conversion efficiency up to 17.10% and an average operational lifetime over 200 h. These uniform sputtered SnO2 thin films with improved characteristics are promising for large photovoltaic modules and advanced optoelectronic devices.

SnO2-Based Optoelectronic Synapses for Artificial Visual Applications

Optoelectronic synapse units have been drawing a strong interest lately due to their obvious crucial role in the evolution of optoelectronic integration-based neuromorphic computing. Here, optoelectronic synaptic devices are fabricated based on stannic oxide (SnO2) film and with the structure of ITO/SnO2/P++-Si. Using optical stimulation, we found that the synaptic sandwich devices are highly responsive and exhibit fast switching behavior. These optically stimulated synaptic devices accurately could imitate synaptic functions, including paired-pulse facilitation (PPF), excitatory postsynaptic current (EPSC), learning experience behavior, and the conversion from short-term memory (STM) to long-term memory (LTM). The EPSC of such devices could be tuned via light, contributing to an LTM-based analog of optical memory and enhancing learning across affective situations. The work presented here advances the research and manufacture of optoelectronic synapses based on the SnO2 thin films for neuromorphic computing applications.

Defect Location in Laterally Aligned Tin Oxide Nanowires: The Role of Growth Direction, Interface Dimensionality, and Catalyst

Laterally aligned SnO2 nanowires, which exhibit planar growth along crystallographically defined directions of a sapphire substrate surface, are superior for bio- and gas-sensing applications. Little is known about their cross-sectional geometry and the defect distribution within the nanowire cross section, although this substantially determines the electronic properties of the nanowires. In this study, SnO2 nanowires were grown on r-plane sapphire substrates. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) reveal the highly oriented growth of the SnO2 nanowires toward the substrate edges. High-resolution transmission electron microscopy (HRTEM) of the NW cross section and strain mapping allowed for analyzing the crystallographic alignment of the SnO2 NW to the sapphire substrate and the defect distribution within the SnO2 nanowire cross section. These techniques revealed a defect-free SnO2–Al2O3 interface and a high alignment of the SnO2 NW lattice toward the sapphire substrate along the NW width. The determined high defect density close to the nanowire surface will be discussed in comparison to freestanding SnO2 nanowires and SnO2 thin films on sapphire substrates considering the differences in the growth direction and the interface dimensionality.