Search Results (62)

The tin dioxide (SnO₂) thin films in this work were prepared by using plasma-enhanced atomic layer deposition (PEALD), and a systematic analysis was conducted to evaluate the influence of post-deposition annealing at various temperatures in a nitrogen–hydrogen mixed atmosphere on their surface morphology, optical behavior, and electrical performance. The SnO₂ films were characterized by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Hall effect measurements. With increasing annealing temperatures, the SnO₂ films exhibited enhanced crystallinity, a higher oxygen vacancy (O_V) peak area ratio, and improved mobility and carrier concentration. These enhancements make the annealed SnO₂ films highly suitable as electron transport layers (ETLs) in perovskite solar cells (PSCs), providing practical guidance for the design of high-performance PSCs. Full article

Se-doped CdTe thin films were grown employing a simple two-electrode electrochemical deposition method using glass/tin-doped indium oxide (glass/ITO). Cadmium acetate dihydrate [Cd (CH₃CO₂)₂. 2H₂O], selenium dioxide (SeO₂), and tellurium dioxide (TeO₂) were used as precursors. Instruments including X-ray diffraction for structural investigation, UV-Vis spectrophotometry for optical properties, and scanning probe microscopy for morphological properties were employed to investigate the physico-chemical characteristics of the resulting Se-doped CdTe thin-film. The films are polycrystalline with a cubic phase, according to X-ray diffraction (XRD) data. More ions are deposited on the substrate, which makes the material more crystalline and intensifies the characteristic peaks that are seen. It is observed from the acquired optical characterization that the film’s bandgap is greatly influenced by the deposition time. The bandgap dropped from 1.92 to 1.62 as the deposition period increased from 25 to 45 min, making the film more transparent and absorbing less light at shorter deposition durations. Images from scanning electron microscopy (SEM) show that the surface morphology is homogenous with closely packed grains and that the grain forms become less noticeable as the deposition time increases. This work is novel in that it investigates the influence of the deposition time on the structural, optical, and morphological properties of Se-doped CdTe thin films deposited using a cost-effective, simplified two-electrode electrochemical method—a fabrication route that remains largely unexplored for this material system. Full article

In this paper, we investigated fractal cluster structures of colloidal particles in tin dioxide films obtained from lyophilic film-forming systems SnCl₄/EtOH/NH₄OH with different pH levels. It was revealed that at the ratio Sn > Cl₂ > O₂, N₂ = 0, and pH = 1.42, the growth of cross-shaped and flower-shaped structures of various sizes from several μm to tens of μm is observed. At the ratio Cl₂ > Sn > O₂ > N₂ and pH = 1.44, triangular and hexagonal structures are observed, the sizes of which are on the order of several tens of micrometers. The growth of hexagonal structures is probably affected by the presence of nitrogen in the film, according to the elemental analysis data. At the ratio Sn > Cl₂ > O₂ > N₂ and solution pH of 1.49, the growth of hexagonal and cross-shaped structures is observed, whereas flower-shaped structures are not observed. Hierarchical flower-like and cross-shaped structures are fractal. The shape of microstructures is directly related to the shape of the elementary cells of SnO₂ and NH₄Cl. A direct dependence of the formation of hierarchical structures on the volume of ammonium hydroxide additive was found. This allows for controlling the shape and size of the synthesized structures when changing the ratio of the initial precursors and influencing the final physicochemical characteristics of the obtained samples. Full article

This paper aims to enhance the sensitivity of fiber-optic surface plasmon resonance (SPR) sensors by innovatively applying TRIZ (Theory of Inventive Problem Solving). To identify the key challenges faced by current SPR sensors, methods such as functional analysis, causal analysis, and the Nine-Window method are employed. Utilizing TRIZ tools, including Technical Contradiction, Physical Contradiction, the Smart Little Man method, and object–field analysis, innovative solutions are proposed, involving transparent indium tin oxide (ITO) thin films, an asymmetric photonic crystal fiber structure with elliptical pores, and titanium dioxide (TiO₂) thin films. Experimental results reveal a significant improvement in sensitivity, with an average of 9961.90 nm/RIU and a peak of 12,503.56 nm/RIU within the refractive index range of 1.33061 to 1.40008, representing a 456% increase compared to the original gold-film fiber-optic SPR sensor. These findings have potential applications in biosensing, environmental monitoring, and food safety. Full article

This study explores the surface chemistry and electrical responses of ultra-high-sensitivity SnO₂ MEMS arrays to enable a novel sequential detection methodology for detecting nitrogen dioxide (NO₂) and ethanol (C₂H₅OH) as a route to achieve selective gas sensing in electronic nose (E-nose) applications. Utilizing tin oxide (SnO₂) thin films deposited via atomic layer deposition (ALD), the array achieves the lowest reported detection limits of 8 parts per billion (ppb) for NO₂. The research delves into the detection mechanisms of NO₂ and C₂H₅OH, both individually and in subsequent exposures, assessing the sensor’s dynamic response across various operating temperatures. It demonstrates rapid response and recovery times, with averages of 48 s and 277 s for NO₂ and 40 and 48 for C₂H₅OH. Understanding the role of individual gases on the SnO₂ surface chemistry is paramount in discerning subsequent gas exposure behavior. The oxidizing behavior of C₂H₅OH following NO₂ exposure is attributed to interactions between NO₂ and oxygen vacancies on the SnO₂ surface, which leads to the formation of nitrate or nitrite species. These species subsequently influence interactions with C₂H₅OH, inducing oxidizing properties, and need to be carefully considered. Principal component analysis (PCA) was used to further improve the sensor’s capability to precisely identify and quantify gas mixtures, improving its applicability for real-time monitoring in complex scenarios. Full article

This paper presents the results of a study on the characteristics of semiconductor sensors based on thin SnO₂ films modified with antimony, dysprosium, and silver impurities and dispersed double Pt/Pd catalysts deposited on the surface to detect carbon monoxide (CO). An original technology was developed, and ceramic targets were made from powders of Sn-Sb-O, Sn–Sb-Dy–O, and Sn–Sb-Dy-Ag–O systems synthesized by the sol–gel method. Films of complex composition were obtained by RF magnetron sputtering of the corresponding targets, followed by technological annealing at various temperatures. The morphology of the films, the elemental and chemical composition, and the electrical and gas-sensitive properties were studied. Special attention was paid to the effect of the film composition on the stability of sensor parameters during long-term tests under the influence of CO. It was found that different combinations of concentrations of antimony, dysprosium, and silver had a significant effect on the size and distribution of nanocrystallites, the porosity, and the defects of films. The mechanisms of degradation under prolonged exposure to CO were examined. It was established that Pt/Pd/SnO₂:0.5 at.% Sb film with optimal crystallite sizes and reduced porosity provided increased stability of carbon monoxide sensor parameters, and the response to the action of 100 ppm carbon monoxide was G₁/G₀ = 2–2.5. Full article

This article presents the results of the formation of hierarchical micro–nano structures in nanostructured tin dioxide films obtained from the lyophilic film-forming system SnCl₄/EtOH/NH₄OH. The classification of the shape and size of the synthesized structures, in relation to the pH of the solution, is presented. Measurements were carried out on an X-ray diffractometer to study the crystal structure of the samples analyzed. It was found that SnO₂ and NH₄Cl crystallites participate in the formation of the synthesized hierarchical structures. It is shown that the mechanism of the formation of hierarchical structures depends on the amount of ammonium hydroxide added. This makes it possible to control the shape and size of the synthesized structures by changing the ratio of precursors. Full article

In this study, titanium dioxide (TiO₂) was deposited onto a fluorine-doped tin oxide (FTO) substrate using the sol–gel spin coating method. Through the implementation of calcination treatment on the thin film, enhancements were observed in terms of structural, optical, and morphological properties. Various calcination temperatures were explored, with TiO₂ annealed at 600 °C identified as the optimal sample. Analysis of the X-ray diffraction spectroscopy (XRD) pattern revealed the prominent orientation plane of (101), indicating the presence of anatase TiO₂ with a tetragonal pattern at this temperature. Despite fluctuations in the optical spectrum, the highest transmittance of 80% was observed in the visible region within the wavelength range of 400 nm. The estimated band-gap value of 3.45 eV reaffirmed the characteristic of TiO₂. Surface analysis indicated the homogeneous growth of TiO₂, uniformly covering the FTO substrate. Cross-sectional examination revealed a thickness of 263 nm with dense and compact nature of TiO₂ thin film. No presence of defects or pores reflects a well-organized structure and high-quality formation. Significant electrical rectification properties were observed, indicating the successful formation of a p–n junction. In summary, calcination treatment was found to be crucial for enhancing the properties of the thin film, highlighting its significance in the development of solar cell applications. Full article

In this work, we have studied the microstructure and unusual ferromagnetic behavior in epitaxial tin dioxide (SnO₂) films implanted with 40 keV Co⁺ ions to a high fluence of 1.0 × 10¹⁷ ions/cm² at room or elevated substrate temperatures. The aim was to comprehensively understand the interplay between cobalt implant distribution, crystal defects (such as oxygen vacancies), and magnetic properties of Co-implanted SnO₂ films, which have potential applications in spintronics. We have utilized scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), differential thermomagnetic analysis (DTMA), and ferromagnetic resonance (FMR) to investigate Co-implanted epitaxial SnO₂ films. The comprehensive experimental investigation shows that the Co ion implantation with high cobalt concentration induces significant changes in the microstructure of SnO₂ films, leading to the appearance of ferromagnetism with the Curie temperature significantly above the room temperature. We also established a strong influence of implantation temperature and subsequent high-temperature annealing in air or under vacuum on the magnetic properties of Co-implanted SnO₂ films. In addition, we report a strong chemical effect of ethanol on the FMR spectra. The obtained results are discussed within the model of two magnetic layers, with different concentrations and valence states of the implanted cobalt, and with a high content of oxygen vacancies. Full article

The acid etching mechanism of FTO film using zinc powders has been explored, and sulfuric and hydrochloric acid solutions of different concentrations were tested as etching agents. Compact and mesoporous films of titanium dioxide were prepared by spin-coating and doctor blade techniques on FTO glass. Tin sulfide films were formed through a successive ionic layer adsorption and reaction (SILAR) process using different numbers of deposition cycles, and TiO₂/SnS nanocomposites were synthesized. The thin films and the prepared composites were characterized using X-ray diffraction, UV-Vis spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses. In this study, the principal characteristics of deposited tin sulfide films on two different types of TiO₂ films are shown. Full article

Tin dioxide (SnO₂) has recently been recognized as an excellent electron transport layer (ETL) for perovskite solar cells (PSCs) due to its advantageous properties, such as its high electron mobility, suitable energy band alignment, simple low-temperature process, and good chemical stability. In this work, nitrogen-doped graphene quantum dots (N-GQDs) were prepared using a hydrothermal method and then used to fabricate N-GQD:SnO₂ nanocomposite ultrathin films. N-GQD:SnO₂ nanocomposite ultrathin films were investigated and applied as electron transport layers in planar PSCs. The presence of N-GQDs with an average size of 6.2 nm in the nanocomposite improved its morphology and reduced surface defects. The excitation–emission contour map indicated that the N-GQDs exhibited a remarkably enhanced light-harvesting capability due to the possibility of absorbing UV light and producing emissions in the visible range. The quenching of photoluminescence spectra showed that the N-GQDs in nanocomposite ultrathin films improved electron extraction and reduced charge recombination. As a result, the power conversion efficiency (PCE) of our planar PSCs fabricated with the optimized N-GQD:SnO₂ nanocomposite electron transport layer was improved by 20.4% over pristine SnO₂-based devices. Full article

This work reports the effect of tin (Sn) doping on the infrared (IR) and terahertz (THz) properties of vanadium dioxide (VO${}_2$) films. The films were grown by hydrothermal synthesis with a post-annealing process and then fully characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and temperature-controlled electrical resistivity as well as IR and THz spectroscopy techniques. Utilizing (NH${}_4$)${}_2$SnF${}_6$ as a Sn precursor allows the preparation of homogeneous Sn-doped VO${}_2$ films. Doping of VO${}_2$ films with Sn led to an increase in the thermal hysteresis width while conserving the high modulation depth in the mid-IR regime, which would be beneficial for the applications of VO${}_2$ films in IR memory devices. A further analysis shows that Sn doping of VO${}_2$ films significantly affects the temperature-dependent THz optical properties, in particular leading to the suppression of the temperature-driven THz transmission modulation. These results indicate Sn-doped VO${}_2$ films as a promising material for the development of switchable IR/THz dichroic components. Full article

Tin oxide (SnO₂) and titanium dioxide (TiO₂) are recognized as attractive energy materials applicable for lead halide perovskite solar cells (PSCs). Sintering is one of the effective strategies for improving the carrier transport of semiconductor nanomaterials. Using the alternative metal-oxide-based ETL, nanoparticles are often used in a way that they are dispersed in a precursor liquid prior to their thin-film deposition. Currently, the creation of PSCs using nanostructured Sn/Ti oxide thin-film ETL is one of the topical issues for the development of high-efficiency PSCs. Here, we demonstrate the preparation of terpineol/PEG-based fluid containing both tin and titanium compounds that can be utilized for the formation of a hybrid Sn/Ti oxide ETL on a conductive substrate (F-doped SnO₂ glass substrate: FTO). We also pay attention to the structural analysis of the Sn/Ti metal oxide formation at the nanoscale using a high-resolution transmission electron microscope (HR-TEM). The variation of the nanofluid composition, i.e., the concentration of tin and titanium sources, was examined to obtain a uniform transparent thin film by spin-coating and sintering processes. The maximum power conversion efficiency was obtained for the concentration condition of [SnCl₂·2H₂O]/[titanium tetraisopropoxide (TTIP)] = 25:75 in the terpineol/PEG-based precursor solution. Our method for preparing the ETL nanomaterials provides useful guidance for the creation of high-performance PSCs using the sintering method. Full article

Tin dioxide (SnO₂) is one of the most used materials for sensing applications operating at high temperatures. Commonly, “undoped SnO₂” is made by precursors containing elements that can have a deleterious impact on the operation of SnO₂ sensors. Here, we employ experimental and theoretical methods to investigate the structural properties and electronic structure of the rutile bulk and surface SnO₂, focusing on unintentional doping due to precursors. Unintentional doping from precursors as well as intrinsic doping can play an important role not only on the performance of gas sensors, but also on the properties of SnO₂ as a whole. The theoretical calculations were performed using density functional theory (DFT) with hybrid functionals. With DFT we examine the changes in the electronic properties of SnO₂ due to intrinsic and unintentional defects and we then discuss how these changes affect the response of a SnO₂-based gas sensor. From an experimental point of view, we synthesized low-cost SnO₂ thin films via sol–gel and spin-coating processes. To further enhance the performance of SnO₂, we coated the surface with a small amount of platinum (Pt). The crystalline structure of the films was analyzed using x-ray diffraction (XRD) and scanning electron microscopy (SEM), while for the determination of the elements contained in the sample, X-ray photoelectron spectroscopy (XPS) measurements were performed. Furthermore, we investigated the effect of temperature on the band structure of SnO₂ in air, in a vacuum and in nitrogen and hydrogen chemical environments. To optimize the response, we used current–voltage characterization in varying environments. The aim is to associate the response of SnO₂ to various environments with the changes in the band structure of the material in order to gain a better understanding of the response mechanism of metal oxides in different pressure and temperature environments. We found that the resistance of the semiconductor decreases with temperature, while it increases with increasing pressure. Furthermore, the activation energy is highly affected by the environment to which the thin film is exposed, which means that the thin film could respond with lower energy when exposed to an environment different from the air. Full article

Non-conventional crystallization techniques have been developed in recent years. Non-conventional crystallization techniques use primary structural elements (for example, clusters) rather than atoms and molecules. Modern nanomaterial science is going through great changes as an entirely new approach of non-conventional growth mechanisms is emerging due to cluster coupling, catalyzing interest in cluster physics. The formation of fractal and percolation clusters has increased. We carried out step-by-step modeling and an experimental study of the formation of fractal and percolation clusters based on tin dioxide and silicon dioxide and formed by sol–gel technology. In this paper, the growth of fractal aggregates (clusters) from sol particles SnO₂ and SiO₂ based on the modified models of diffusion-limited and cluster–cluster aggregation is discussed. A percolation model using simulated fractal clusters of SnO₂ and SiO₂ particles is proposed. Experimental data on the sol–gel percolation structure of porous nanocomposites are presented. The modeling of SnO₂ and SiO₂ particles, which also consist of clusters (the next step in the hierarchy), is shown. We propose a generalized hierarchical three-dimensional percolation cluster model that allows calculating the surface area, knowing the experimental sizes of macropores and taking into account the micro- and mesopores (sizes less than a few nanometers). Full article