SnO2 Phase Research Articles

Fabrication of Cu2ZnSnS4 (CZTS) by co-electrodeposition of Cu-Zn-Sn alloys, and effect of chemical composition of CZTS on their photoelectrochemical water splitting

Sulfide kesterite Cu2ZnSnS4 (CZTS), an intrinsic p-type semiconductor, provides an attractive low-cost, environmentally friendly photoelectrochemical (PEC) water splitting to evolve hydrogen. The purpose of this study was to clarify the effect of the chemical composition of CZTS on the PEC properties and the correlation with their structures. The CZTS was fabricated on a Mo/glass by a non-vacuum process, i.e., co-electrodeposition (co-ED) of Cu-Zn-Sn (CZT) alloys, followed by sulfurization with solid sulfur. To optimize the chemical composition of CZTS, the bath concentrations, applied potentials and amounts of electric charge for preparation conditions of the CZT precursors were examined. The CZTS with Cu-poor and Sn-rich composition compared with stoichiometry was found to exhibit relatively effective PEC water splitting. It was suggested that the high PEC performance was attributed to efficient charge carrier transport due to the presence of a small amount of SnO2 phase on the CZTS surface.

Effect of oxygen flow ratio on the performance of RF magnetron sputtered Sn-doped Ga2O3 films and ultraviolet photodetector

This work explored the properties of RF magnetron sputtered Sn-doped Ga2O3 films grown on sapphire substrates at different oxygen flow ratios from 0.0 to 2.5%. The in situ optical emission spectroscopy was conducted to monitor the plasma radicals generated during the films’ deposition. All the films deposited at room temperature show amorphous structures with some nanoparticles. The deposition rate decreased monotonically with increasing oxygen flow ratio. The proposed conductive mechanism of the films can be mainly attributed to the changes in the ratio of substitutional Sn (Sn4+ valance state) atoms replacing lattice Ga sites (Ga3+ valance state) and the SnO2 phase in the films. Metal–semiconductor–metal solar-blind photodetectors were developed and analyzed to illustrate the effect of oxygen flow ratio. A high performance photodetector with a low dark current of 1.14 pA, high on/off ratio of 812 and short rise/decay time of 0.05 s/0.12 s was realized at an optimization growth condition. The elaboration of the conductive mechanism and effect of oxygen flow ratio on the performance of Sn-doped Ga2O3 films and their photodetectors is crucial for the preparation of high-quality Sn-doped Ga2O3 films and its application in optoelectronic devices.

Improving the p-Type Conductivity and Transparency of Pure Phase SnO by Ga and Na Doping

Tin monoxide (SnO) has attracted much attention as a p-type transparent conducting oxide (TCO) with high hole mobility, which was attributed to its relatively delocalized valence band. Nominally undoped SnO can achieve a free hole concentration of >1018 cm–3 due to the low formation energy of the Sn vacancy acceptor. Although several calculations showed that many acceptors have low formation energies and were considered efficient acceptors in SnO, very few experimental works have been reported. In this work we explore the electrical and optical properties of Ga- and Na-doped SnO thin films synthesized by room temperature magnetron sputtering. We find that all as-grown films are amorphous and insulating but become polycrystalline with a tetragonal structure after post-growth rapid thermal annealing (RTA) at temperatures >400 °C. While the resistivity ρ of pure phase SnO is slightly lowered from ∼0.9 Ω·cm for undoped to ∼0.2 Ω·cm with 1.2% Ga doping, a much lower ρ of ∼0.01 Ω·cm with a high hole concentration of 4–5 × 1019 cm–3 and a high mobility of >10 cm2/(V·s) can be achieved with ∼2.3–2.8% Na doping. However, the visible transparency Tvis of these highly p-type SnO:Na is only ∼50%, lower than the ∼65% of SnO:Ga films. This is likely due to the presence of excess Sn in SnO:Na films. Detailed variable temperature Hall measurements reveal that the acceptor ionization energies for the substitutional Ga and Na (GaSn and NaGa) to be 52 ± 3 and 20 ± 5 meV, respectively. Moreover, all films have a wide band gap of ∼2.7–2.9 eV. We believe that with further optimization in the growth and annealing process, SnO:Na films with ρ < 10–2 Ω·cm and Tvis > 65% can be realized. These results demonstrate that Ga and Na are effective acceptors in SnO, where Na acceptor has a lower formation as well as ionization energies and, hence, can achieve a higher free hole concentration and lower resistivity. Therefore, with appropriate doping, SnO is a high-performance p-type transparent oxide that has technological potential for the advancement of transparent optoelectronics.

In situ construction of SnO-NiO derived from metal-organic frameworks on nickel foam for energy storage devices

Background: Metal-organic frameworks (MOFs) have concerned substantial research attention as potential electrode materials in the field of electrochemical storage owing to their high porosity. However, their low cycling stability and rapid capacity fading hinder the practical application of MOFs because of the structural instability of the electrodes during cycling. Existing studies have shown that MOF-derived materials are helpful in improving their performance due to controllable functionalities, permanent porosities, and high surface area.Methods: We demonstrated an efficient strategy to solve these problems by combining the beneficial redox properties of Sn and Ni metal precursor and benzene-1,3,5-tricarboxylate (BTC) organic linker. SnONiO derived from Sn-Ni MOFs were in situ deposited on nickel foam (i.e., Sn-Ni MF@Ni nanostructures) by solvo-hydrothermal approach.Significant findings: The all-solid-state asymmetric supercapacitor device, Sn-Ni MF@Ni//AC, exhibited excellent electrochemical storage capacity (214.67 F/g at 1.0 A/g) and excellent high-rate cycling stability of 90% over 6000 cycles. The Sn-Ni MF@Ni//AC nanostructured device exhibited high energy and power densities of 66.87 Wh/kg at 747.67 W/kg, respectively, at a discharge time of 322 s. The remarkable electrochemical storage properties of Sn-Ni MF@Ni nanostructures can be attributed to their unique SnO and NiO bimetallic oxide phases on NF substrates. They are comparable to those of drop-cast Sn-Ni MFs on NF electrodes.

Production of biodiesel from waste cooking oil using mesoporous MgO-SnO2 nanocomposite

Mesoporous, bifunctional MgO-SnO2 nanocatalysts with enhanced surface area are used for producing biodiesel from waste cooking oil. Biodiesel with yield of 80% is achieved within the first 20 min when transesterification is carried out at an optimum condition of 18:1 methanol to oil ratio, 2 wt% of nanocatalyst, and at a reaction temperature of 60 °C. The conversion gives a maximum yield of 88% when transesterification is allowed to continue for 120 min. The waste cooking oil used in this work is dominated with linoleic acid and oleic acid, which during transesterification gets converted into methyl linoleate and 9-octadecenoic acid methyl ester. These nanocatalysts are fabricated using a composite of rutile (tetragonal) phase SnO2 and cubic phase MgO nanostructures with prominent crystal orientation along [211] and [200] plane respectively. The MgO-SnO2 nanocomposites with an enhanced surface area of 31 m2/g, basic sites of 2 mmol/g, and particle size of ~15 nm are synthesized by novel sequential thermal decomposition and sol-gel technique. The synthesized wide band gap nanocomposites have Mg and Sn in the ratio of 15:1 and do not have any impurity phases as observed in the X-ray diffraction pattern and EDS spectrum. The presence of surface oxygen states and Mg2+ and Sn4+ oxidative states is responsible for the catalytic activity and recyclability displayed by the composites. This work signifies the role of nanocomposites and their synthesis conditions in improving the rate of transesterification. These metal oxide nanocomposites which are nontoxic, stable, cost effective, and easier to synthesis are promising catalysts for large-scale transesterification of waste cooking oil to biodiesel.

Room-Temperature Fabrication of p-Type SnO Semiconductors Using Ion-Beam-Assisted Deposition.

Over the past decade, SnO has been considered a promising p-type oxide semiconductor. However, achieving high mobility in the fabrication of p-type SnO films is still highly dependent on the post-annealing procedure, which is often used to make SnO, due to its metastable nature, readily convertible to SnO2 and/or intermediate phases. This paper demonstrates a fully room-temperature fabrication of p-type SnOx thin films using ion-beam-assisted deposition. This technique offers independent control between ion density, via the ion-gun anode current and oxygen flow rate, and ion energy, via the ion-gun anode voltage, thus being able to optimize the optical band gap and the hole mobility of the SnO films to reach 2.70 eV and 7.89 cm2 V-1 s-1, respectively, without the need for annealing. Remarkably, this is the highest mobility reported for p-type SnO films whose fabrication was carried out entirely at room temperature. Using first-principles calculations, we rationalize that the high mobility is associated with the fine-tuning of the Sn-rich-related defects and lattice densification, obtained by controlling the density and energy of the oxygen ions, both of which optimize the spatial overlap of the valence bands to form a continuous conduction path for the holes. Moreover, due to the absence of the annealing process, the Raman spectra reveal no significant signatures of microcrystal formation in the films. This behavior contrasts with the case involving the air-annealing procedure, where a complex interaction occurs between the formation of SnO microcrystals and the formation of SnOx intermediate phases. This interplay results in variations in grain texture within the film, leading to a lower optimum Hall mobility of only 5.17 cm2 V-1 s-1. Finally, we demonstrate the rectification characteristics of all-fabricated-at-room-temperature SnOx-based p-n devices to confirm the viability of the p-type SnOx films.

A comparative study on the photocatalytic activity and formation mechanism of nanostructured Cu2ZnSnS4 prepared by thermal and mechano-thermal methods

In this paper, a nanostructured Cu2ZnSnS4 (CZTS) was synthesized from elemental constituents through two simple methods: thermal and mechano-thermal. The thermal analysis was applied to determine the appropriate heat treatment conditions. Wet ball milling was employed in mechano-thermal synthesis to obtain a uniform activated powder, and the optimum conditions were investigated. The X-ray diffraction (XRD) and Raman results confirmed the formation of kesterite structure CZTS after annealing the mixture at 550 °C for 1 h in thermal synthesis, while the annealing temperature for CZTS formation is reduced to 410 °C in mechano-thermal synthesis. For mechano-thermally synthesized sample, the scanning electron microscopy (SEM) and the transmission electron microscopy (TEM) results showed the agglomerated powders with average particle sizes of 123 and 139 nm, respectively. The surface and optical properties of samples were compared through Brunauer-Emmett-Teller (BET), diffusion reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. DRS results demonstrated considerable absorbance over the entire range of visible light wavelengths with bandgap energies of about 1.48–1.51 eV. The photocatalytic activities of synthesized samples, degradation kinetics and mechanisms, and the effect of SnO2 phase formation have been investigated through photodegradation of methylene blue (MB) dye under visible light irradiation. The optimum mechano-thermally synthesized sample as the photocatalyst led to 94% degradation after 120 min. Mechanism explained by scavenger studies revealed that holes were the main reactive radicals responsible for the degradation process.

Facile strategy for advanced selectivity and sensitivity of SnO2 nanowire-based gas sensor using chemical affinity and femtosecond laser irradiation

This study proposes an effective strategy to improve the selectivity and response of SnO2 nanowire (NW)-based gas sensors. Self-assembled monolayer (SAM) functionalization of SnO2 NWs enhances the gas selectivity by tuning the surface chemical states. Different chemical moieties with alkyl and fluoroalkyl of the SAM molecules are adopted for the chemical affinities toward the corresponding target gas molecules. The alkyl and fluoroalkyl moieties show excellent selectivity toward CH4 and C3F8, respectively, owing to the strong chemical affinity between the moieties and gases. Post-treatment femtosecond (FS) laser irradiation with different laser fluences is applied to the SAM-functionalized SnO2 NW-based gas sensor. The FS laser-irradiated SnO2 NWs show an enhanced sensor response with higher resistance values and shorter response and recovery times compared to those of the pristine SnO2 NWs. Transmission electron microscopy analysis reveals that the FS laser irradiation induces the formation of embossing surface on the SnO2 NW, creating additional gas adsorption sites. Moreover, twin structures develop on the SnO2 NWs with increasing laser fluences. Electron energy loss spectroscopy analysis supports that the FS laser irradiation creates non-stoichiometric SnO and SnOx phases, providing O vacancies and improved response.

Sintering densification behavior of ZnO–SnO2 binary ceramic targets

AbstractIn this work, high‐performance ZnO–SnO2 binary ceramic targets for magnetron sputtering of transparent conductive oxide (TCO) films were prepared by pressureless oxygen atmosphere sintering. The sintering behavior and densification mechanism of the ZnO–SnO2 binary targets were analyzed by systematically studying the oxide powder state, formation process of the solid reaction phase, and evolution of the target microstructure. The data revealed that the ZnO–SnO2 powder treatment improved the sintering activity and the powder dispersion; furthermore, it promoted a mutual reaction between the different components during sintering and the homogeneity of the target composition. The densification of the pure SnO2 ceramic target was difficult to achieve, and the addition of ZnO led to a continuous interaction between the ZnO and SnO2 components. The Zn2SnO4 phase started to form, and a temporary shrinkage of the target occurred above 800°C. After formation of the stable Zn2SnO4 and SnO2 phases, the target shrunk rapidly with increasing temperature, densification occurred during growth, and the two phases started to interact. The sintering temperature provided the driving force for the target densification, with the densification activation energy of the ZnO–SnO2 binary ceramic target estimated to be 580 kJ/mol based on the master sintering curve. A binary ceramic target with a high density (99.78% relative density), a fine grain size, and a homogeneous phase structure was achieved at a temperature of 1600°C. These findings are promising for the further improvement and performance enhancement of SnO2‐based materials.

Effects of Cobalt Doping on the Structural, Optical, and Electrical Properties of SnO2 Nanostructures Synthesized by SILAR Method

Undoped and cobalt (Co) doped tin oxide (SnO2) films were prepared onto glass slides via the successive ionic layer adsorption and reaction (SILAR). Variable characterization methods were applied to examine the effects of cobalt impurities on physical properties of SnO2 films. The performed characterization measurements were X-ray diffraction, Ultraviolet–visible spectrometer, Photoluminescence, and Raman. No peak ascribed to Co, SnO, or Sn was found in the XRD spectrum which may indicate the integration of cobalt in SnO2 crystal lattices. And the obtained XRD peaks may be related to the tetragonal rutile phase of pure SnO2. SEM images exposed that the Co dopant atoms affectedthe sample morphologies. The optical analyses showed that the transmittance and reflectance percentages dropped by the introduction of impurities to the SnO2 system as the absorbance values of doped SnO2 samples increased. Thus,a red shift (2.6–1.8 eV) occurred in the bandgapsas Co concentration changed in the films. The Raman spectra of pure SnO2 and Co:SnO2 samples exhibited major peaksaround 481 cm−1, 571 cm−1 and 602 cm−1. In photoluminescence spectrum, it was noted that the emission intensity can both increase or decrease due to the different cobalt doping ratios in the SnO2 nanostructures. Resistance measurements displayed that the resistivity increased with the increment of doping concentration. However, it was shown that the electrical conductivities could be increased after the heat treatment of glass substrates up to 500 oC, a common behavior of semiconductor materials.

Deposition Mechanism and Characterization of Plasma-Enhanced Atomic Layer-Deposited SnOx Films at Different Substrate Temperatures.

The promising functional tin oxide (SnOx) has attracted tremendous attention due to its transparent and conductive properties. The stoichiometric composition of SnOx can be described as common n-type SnO2 and p-type Sn3O4. In this study, the functional SnOx films were prepared successfully by plasma-enhanced atomic layer deposition (PEALD) at different substrate temperatures from 100 to 400 °C. The experimental results involving optical, structural, chemical, and electrical properties and morphologies are discussed. The SnO2 and oxygen-deficient Sn3O4 phases coexisting in PEALD SnOx films were found. The PEALD SnOx films are composed of intrinsic oxygen vacancies with O-Sn4+ bonds and then transformed into a crystalline SnO2 phase with increased substrate temperature, revealing a direct 3.5–4.0 eV band gap and 1.9–2.1 refractive index. Lower (<150 °C) and higher (>300 °C) substrate temperatures can cause precursor condensation and desorption, respectively, resulting in reduced film qualities. The proper composition ratio of O to Sn in PEALD SnOx films near an estimated 1.74 suggests the highest mobility of 12.89 cm2 V−1 s−1 at 300 °C.

Influence of post-deposition annealing on the novel alloyed SnSxO1-x semiconductor in p-type thin-film transistors

SnO is an oxide semiconductor that has the potential to be used in the development of thin-film transistors (TFTs) with a p-type channel. SnO on the other hand is a metastable phase, and the oxidation of the SnO films makes high-performance TFTs with good mobility and high on/off current ratios challenging. In this study, based on the SnO–SnO2 phase transformation mechanism, a novel alloyed semiconductor SnSxO1-x was reported to prevent the conversion of SnO to SnO2. Pulsed laser deposition was used to grow SnO and SnSxO1-x thin films on Si/SiO2 substrates, which were then exposed to rapid annealing procedures. From Raman spectroscopic analysis, SnSxO1-x exhibited better antioxidant performance than pure SnO at the same post-deposition annealing process. The developed SnSxO1-x TFTs exhibited better stability and an improved on/off ratio than SnO TFTs after high-temperature annealing. Additionally, we fabricated bilayer SnSxO1-x/SnO thin-film transistors with typical p-channel conduction and a 10−11 A off-state current.

Concurrent Synthesis of Functional SnO2/SnO Composite for Proton Conductive Sensor and Photo-Catalytic Treatment

The hybrid materials have great significance in gas detection, photocatalysis and humidity sensing. In this paper, the SnO2/SnO material was successfully obtained by annealing Sn6O4(OH)4 at 350°C. The Sn6O4(OH)4 sample was synthesized by the co-precipitation method. The XRD analysis confirmed the formation of SnO2 and SnO phases and XPS analysis validated the results of XRD analysis (presence of the Sn2+ and Sn4+ states). The N2 adsorption-desorption isotherm revealed the mesoporous characteristic of the material along with 41.386 m2 g−1 BET surface area and 3.794 nm average pore diameter. As a sensing application, a sensor based on SnO2/SnO material was fabricated on the interdigitated electrodes and investigated under combined atmospheres of humidity levels (11%RH—33%–95%RH—11%RH) and ammonia (200–1200 ppm). The response and recovery times for the maximum response (under 11%RH–95%RH—11%RH and 1200ppm NH3) were 7 s and 26 s, respectively. The experimental observations confirmed that the resistance of the sensor depends on the concentration of H2O and NH3, both form the conjugate acid-base pair and which is responsible for the response of the sensor. Moreover, SnO2/SnO material as a catalyst possessed the good results for the degradation of MB (96%) and MO (84%) under visible light source.

Nanocomposite based hydroelectric cells: Working principle and production of green electrical energy

Hydroelectric cells were prepared to produce the electricity through the splitting of water molecules into hydronium and hydroxide ions at room temperature. Hydroelectric cells of WO3 loaded SnO2 nanocomposite produce electricity without emission of any toxic gas or by-products. The structural, morphological and hydroelectric properties of the nanocomposites were analyzed by using powder X-ray diffraction, Scanning Electron Microscope, Fourier Transform Infra-red Spectra. Adsorption-desorption isothermal curves, pore size distribution and pore volume were investigated by using Barrett‐Joyner‐Halenda technique. Ionic diffusion of the dissociated H3O+ and OH– ions have been investigated by dielectric and dc conductivity measurements of all the samples in dry and wet states. Powder X-ray Diffraction pattern validates the biphasic composite having monoclinic WO3 phase and tetragonal SnO2 phase. Surface chemical analysis and oxygen defect study were investigated using X-ray photoelectron spectrum. The uniform grain distribution along with well crystalline morphology was observed by SEM micrographs. Circular cells of WO3 loaded SnO2 nanocomposite samples of 2-inch diameter have been prepared to investigate the hydroelectric properties. The fabricated HEC of 19.63 cm2 area of 10 wt% WO3 loaded SnO2 nanocomposite delivers maximum short circuit current, open-circuit voltage and off-load output power as 655 mA, 0.959 V, 628 mW, respectively. Output power exhibited by WO3 - SnO2 nanocomposite based Hydroelectric Cell is considerable and has appeared as a feasible green energy source.

Synthesis of Hexahydroxy Strontium Stannate/Tin Dioxide Nanocomposites and their Photocatalytic Properties for Gentian Violet

Background: Gentian violet dye released from industries into the environment has caused serious water pollution and is a significant environmental pollutant to human beings owing to the toxicity. It is urgent to decrease environmental pollution by removing gentian violet in the wastewater. Objective: The aim is to synthesize hexahydroxy strontium stannate/tin dioxide nanocomposites by a simple hydrothermal method without surfactants and research the photocatalytic performance for gentian violet degradation. Methods: Hexahydroxy strontium stannate/tin dioxide nanocomposites have been obtained via the hydrothermal method. The structure, size, morphology and photocatalytic performance were characterized by X-ray diffraction, electron microscopy, solid ultraviolet-visible diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. Results: The nanocomposites possess oven-shaped morphology with the size of less than 100 nm and are composed of hexagonal SrSn(OH)6 and tetragonal SnO2 phases. The band gap of the nanocomposites is 3.52 eV. 10 mg hexahydroxy strontium stannate/tin dioxide nanocomposites have the ability to completely degrade 10 mL gentian violet solution with the concentration of 10 mgL-1 under 6 h ultraviolet-visible light irradiation. Hydroxyl radical, hole and superoxide radical are the main species for the gentian violet photocatalytic degradation using the nanocomposites. Conclusion: The hexahydroxy strontium stannate/tin dioxide nanocomposites show good photocatalytic performance for the GV degradation. The photocatalytic performance for gentian violet degradation using the hexahydroxy strontium stannate/tin dioxide nanocomposites depends on the irradiation time and content of the nanocomposites.

Effect of surface treatment on microstructure and chemical composition of indium tin oxide targets

In order to deepen understanding of oxide targets, high-density indium tin oxide (ITO) targets are prepared via oxygen sintering. ITO targets are subjected to different etching treatments, namely acid etching and thermal etching. Effects of different etching treatments on microstructure, composition, and chemical state of targets are studied. Results show that different treatments result in different microstructural characteristics of the target, i.e., grain boundaries, secondary phases, precipitated phase particles, and pores. Due to decomposition of In4Sn3O12 phase grains during thermal etching, grain size of secondary phase (2.5 μm) obtained after thermal etching is smaller than that obtained after acid etching (3.13 μm). After acid etching, fine particles in primary phase grains are precipitated from supersaturated solid solution. After thermal etching, quadratic grains characteristics of SnO2 phase are observed alongside low proportion of In4Sn3O12 phase due to eutectoid decomposition reaction of In4Sn3O12 phase during thermal etching. Compositional characteristics of original target can be more easily retained via acid etching than thermal etching. These findings are meaningful for understanding material characteristics of ITO targets to improve their microstructure and performance.

MnO2-SnO2 Based Liquefied Petroleum Gas Sensing Device for Lowest Explosion Limit Gas Concentration

In this work, MnO2-SnO2 nanocomposite based below lower exposure limit (0.5–2.0 vol%) sensing device for liquefied petroleum gas (LPG) is reported. The synthesized material is highly crystalline with an average crystallite size of 16.786 nm, confirmed by the X-ray diffraction pattern. Williamson-Hall plot shows that the induced strain of 2.627 × 10−4, present in the nanocomposite, lies between the induced strains of both of its constituents. The XRD pattern of nanocomposite contains the cubic phase of MnO2 and the tetragonal phase of SnO2. Tauc plot shows the optical energy band gap of MnO2, SnO2, and MnO2-SnO2 of 3.407 eV, 3.037 eV, and 3.202 eV respectively. The surface morphological investigation shows the brush-like structure which enhances sensor performance by providing activation sites. The energy dispersive X-ray (EDS) spectrum found that materials are highly pure because other peaks are not observed. The functional group analysis by using FTIR found to be Sn–O and Mn–O both vibration bands existed. The highest sensor response was found to be 2.42 for 2.0 vol% whereas for a lower concentration of 0.5 vol% the sensor response was observed to be 1.44. The fast response and recovery of this sensing device were found to17.30 and 23.25 s respectively for 0.5 vol% of LPG.

Annealing induced morphology evolution and phase transition in SnOx thin films grown by e-beam evaporation method

In the present work, we demonstrate the growth of tin oxide (SnOx) thin films using electron beam evaporation method to study the phase transition from stannous oxide (SnO) to stannic oxide (SnO2) by varying annealing temperature (i.e., from 300 to 700 °C). Annealing induced morphology evolution and structural modifications stimulate the process of phase-transformation, which is primarily discussed by divided the entire temperature range into two-regimes. Regime-A (from 300 to 400 °C) consists of tetragonal α-SnO dominated phase, regime-B (from 600 to 700 °C) exhibits orthorhombic pure SnO2 phase. However, these regimes are being separated by an interface conferring a mixed-phase of tin oxides at an annealing temperature ∼500 °C. This temperature-dependent phase-inversion is adequately controlled by tuning the morphological, structural and optical properties of SnOx thin films to develop homo/heterostructures for various photovoltaic and optoelectronic applications.

Broadband (NIR-Vis-UV) photoresponse of annealed SnSe films and effective oxidation passivation using Si protective layer

Tin selenide is a versatile material with superior thermoelectric properties and can compete for optoelectronics, gas sensing, etc. As the actual application of the device depends upon the stability of the material under practical conditions (like for thermoelectric application, the material must be stable up to the defined temperature at which ZT is maximum). This paper reports the material's systematic thermal and chemical stability for feasible, practical applications in optoelectronic and thermoelectric aspects. SnSe film was deposited on the soda-lime glass substrate using thermal evaporation. Annealing was carried out at different temperatures (200, 250, and 300 °C) for one hour in open-air conditions. With the increase in the annealing temperature, part of the SnSe phase was initially changed to the SnSe2 phase, and a tin dioxide layer was formed (confirmed by Raman spectroscopy). A blue shift in the direct bandgap (from 1.35 eV, for pure SnSe to 1.84 eV, for 300 °C annealed SnSe) has been observed with an increase in annealing temperature. Atomic force and scanning electron microscopic studies have been carried out. Samples annealed at 300 °C showed a broadband spectral response due to crystalline SnSe, SnSe2, and SnO2 phases. Also, the formation of three consecutive layers viz SnSe, SnSe2, and SnO2 can be used for solar cell applications. Further, deposition of Si as a protective layer on the SnSe for improved oxidation stability has been carried out, which resisted the oxidation up to 250 °C.

Influence of reducing agents in nanoparticle synthesis: SnO2‐ZnO composite anode

AbstractThe present research work is dedicated to understand the effect of synthesis medium on the nanocomposite anode, SnO2: ZnO, and their synergistic effects towards Li‐ion battery applications. Alkaline and acidic media as reducing agents such as NaOH, LiOH, and NaBH4 are chosen for the preparation of the composite, and the results are surprisingly varying. Structural analysis by means of X‐ray diffraction shows the mixed crystal symmetry inclusive of SnO2 and ZnO phases for all the three systems with varying ranges of each phases. The average crystallite sizes are around 20–39 nm for all the three samples. Morphological analysis of SnO2: ZnO anode by means of transmission electron microscopy indicates mixed shapes of grains for the samples synthesized by NaOH and LiOH, whereas reducing agent, NaBH4, falls into the spherical shape predominantly. Raman and selected area electron diffraction analyses validate the mixed crystal symmetry of all the three samples. Electrochemical performance of the samples is promising where NaBH4 mediated anode delivers reversible capacity around 225 m Ahg−1 exclusively. In the aspect of electrical conductivity, almost all the three samples employed with three different reducing agents fall in the range of ~10−4 S cm−1 at room temperature, validating the choice of the material as anode in Li‐ion battery technology.