Polycrystalline Tetragonal Structure Research Articles

An investigation of glass, ITO, and quartz transparent substrates on Pd/SnO2 hydrogen sensor structure and sensitivity

Hydrogen energy has great potential as a fuel for the future, but its leakage poses a major threat. Thus, our main concern is to detect it very quickly. In this work, we investigate the effect of transparent glass, ITO, and quartz substrates on hydrogen gas sensing properties of magnetron sputter- deposited Pd-capped SnO2 (Pd/SnO2) thin film sensor material. The XRD study reveals that all Pd-capped SnO2 thin films deposited on different substrates has polycrystalline tetragonal structure. Sensors fabricated on quartz substrates exhibit homogeneous grain distributions at the interface, whereas sensors deposited on ITO and glass substrates have randomly size grains distribution at the interface. Sensors deposited on glass and ITO show lower sensitivity compare to sensors fabricated on quartz substrate at a working temperature of 250°C. The Pd/SnO2 sensor @ quartz shown a maximum response of ∼ 9.3 and better stability toward 500 ppm hydrogen gas, and a fast response/recovery time of 30/26 s for 5 ppm hydrogen gas. The sensor @ quartz substrate shows a small reduction in response and baseline at 60% RH. The sensor fabricated on quartz substrate exhibits better selectivity toward hydrogen gas and significant stability for long duration of three months in high humid conditions. The performance of the Pd/SnO2 thin sensor fabricated on quartz proves that the sensor based on average grains have a wide potential for real hydrogen gas monitoring.

Sol-gel spin-coated Y-doped SnO2 nanostructured thin films for various optoelectronic device applications

The effect of various concentrations of Y-doped SnO2 thin films (Y: SnO2) on structural, optical, and electrical properties was investigated. XRD showed the polycrystalline tetragonal structure of all the films. SEM analysis showed homogenous growth of the films with spherical structure. XPS revealed the oxidation states of Sn, Y, and O, also it provides the presence of oxygen vacancies in Y: SnO2 films. The UV–visible spectrometer studies showed that all the films were above 76% of optical transmittance in the visible region. The optical band gap energy was found to be 3.91 eV for pure SnO2, whereas Y: SnO2 films have shown a decrease of band gap with Y content and reached down to 3.74 eV in 5 at% Y: SnO2 film. The 3 at% Y: SnO2 film showed the lowest sheet resistance (Rsh) of 34.2 Ω/Sq and the highest figure of merit (ɸ) of 3.55 × 10−3 Ω−1 among the others.

Effect of Cobalt Doping on The Structural, Linear and Nonlinear Optical Parameters of Manganese Oxide Thin Layers

AbstractIn this study, undoped and cobalt‐doped manganese oxide Co:Mn3O4 (0, 2, and 4 at%) are elaborated by the spray pyrolysis procedure on glass substrates. The effect of cobalt doping concentrations on the structural, morphological, and optical features (linear and nonlinear) are investigated through the X‐ray diffractometer, Raman spectroscopy, Scanning Electron Microscopy with an attached energy dispersive X‐ray and UV–Vis‐NIR spectrophotometer. The XRD investigations exhibit a polycrystalline tetragonal structure for all Co:Mn3O4 and confirm by Raman results with the distinctive tetragonal mode A1g at 657 cm−1. The SEM images show an increase in roughness as cobalt doping concentration increases. The EDS quantitative analysis revealed the presence of manganese, oxygen, and cobalt. Furthermore, the optical investigation is pursued firstly through the linear optical that showed a decrease in the transmittance, and optical band gap energy as the cobalt concentration increased due to oxygen vacancies and defects and the increase of refractive index from 2.05 to 2.21. Second, the nonlinear optical parameters show a high value of the nonlinear refractive index 3.75 × 10−7 (esu) and the third‐order susceptibility χ3 = 2.2 × 10−8(esu) of Co:Mn3O4(2at%). These values put the Co:Mn3O4(2at%) thin layer as a candidate in the optoelectronic applications as a third‐order nonlinear medium.

Optoelectronic properties and optical transitions in low concentrated aluminum-doped tin oxide thin films

The structural, chemical, surface morphology, and optoelectronic characteristics of Al-doped SnO2 (ATO) films are investigated and a comprehensive analysis of the obtained results is presented. All films are shown to have a polycrystalline tetragonal rutile structure by X-ray diffraction (XRD) measurements, and the single-phase nature of the structure is proved by detailed X-ray photoelectron spectroscopy (XPS) investigations. Two mechanisms of Al incorporation into the SnO2 lattice were evident by XRD and XPS measurements. Comprehensive XPS, XRD, and Hall effect investigations showed a clear relation between the charge carrier concentration, crystallite size, and the concentration of oxygen vacancy defects. Through a comprehensive analysis of the photoluminescence (PL) measurements, we determined the positions of various defect states within the bandgap. Using a thorough analysis of the optical absorption measurements, we have successfully demonstrated the presence of four direct optical transitions with energies ranging from 3.84 to 5.10 eV, and by considering the Moss–Burstein effect and the Urbach tailing phenomenon, it was shown that the first transition energy (E1) corresponds to the direct optical transition across the Γ3+−Γ1+ forbidden energy gap. The other three transitions are ascribed to electronic transitions from the valence band states Γ5− and Γ5+ to different defect states within the bandgap.

Thickness-dependent microstructure, resistive switching, ferroelectric, and energy storage properties of pulsed laser deposited 0.85[0.6Ba(Zr0.2Ti0.8)O3-0.4(Ba0.7Ca0.3)TiO3]-0.15SrTiO3 thin films

In this work, we have studied the effect of thickness on structural, morphological, resistive switching (RS), ferroelectric, and energy storage properties of 0.85[0.6Ba (Zr0.2Ti0.8)O3-0.4(Ba0.7Ca0.3)TiO3]-0.15SrTiO3 (BZCT-STO) thin films deposited by the pulsed laser deposition technique. X-ray diffraction (XRD) analysis suggests that BZCT-STO thin films exhibit a polycrystalline tetragonal structure. The lattice parameters and tetragonality ratio approaching to bulk value with an increase of thickness, confirm strain relaxation in thicker films. SEM analysis reveals a dense columnar structure with a different grain size that varies from 3 nm to 60 nm as thickness increased from 160 to 360 nm. The P-E loops suggest that the relaxor behaviour increases with a decrease of thickness due to interface low dielectric layer, substrate clamping effect, small grain size, and high back switching ratio. The RS effect observed in Pt/BZCT-STO/Au capacitors is attributed to polarization modulation of the Schottky barrier and is found to be significant at low thickness. The effect of electric field and frequency on energy storage properties of BZCT-STO films is also investigated. The Pt/BZCT-STO/Au capacitor with a thickness of 160 nm exhibited 6.0 J/cm3 with an efficiency of 72% at a field of 800 kV/cm. It also exhibited a robust energy storage performance in the frequency range of 50–2000 Hz and also up to 108 cycles passing through the capacitor.

Structural, morphological, and impedance spectroscopy of Tin oxide -Titania based electronic material

A ceramic composite electronic sample (Sn0·6Ti0.4)O2 is processed through solid-state reaction approach. Crystallographic, morphological, and different temperature-frequency-dependent electrical characteristics have been examined. The formation of a crystallographic polycrystalline tetragonal structure has been ensured through X-Ray Diffraction. The hydrophilic porous nature with uniform distribution of grains is ascertained through SEM. The electrical parameters are evaluated across broad temperatures and frequency ranges of 35 °C–450 °C and 1 kHz - 1 MHz respectively. A superior dielectric permittivity (εr: 44,730), low loss tangent (tanδ: 11.074) (for 400 °C, frequency 1 kHz) with enhanced capacitive behaviour are depicted. The conductivity spectrum reveals the nature and mechanism of conduction. The impedance analyzer divulges the realization of the grain and grain boundary effect on the electrical characteristics. The Non-Debye relaxation behaviour is substantiated by an electric modulus analysis. The comprehensive investigations illustrate this component as a capacitive electronic element for humidity sensor applications.

The tin doping effect on the physicochemical and nonlinear optical properties of the manganese oxide (Mn3O4: Sn) thin films

Undoped and tin doped manganese oxide, Mn3-xSnxO4, (x=0, 2, and 4 at %) thin films were successfully elaborated by the chemical route defined in the spray pyrolysis technique and deposited on glass substrates at a temperature of 350 °C. The physicochemical characterization of the thin films was performed using an X-ray diffractometer (XRD) that showed a polycrystalline tetragonal structure for all thin films. Raman measurement confirmed the vibrational mode, A1g, and the XRD results with the presence of no secondary phases. Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy depicted the surface morphology and the elemental composition (Mn, O, and Sn) of the elaborated thin films. Finally, the optical analysis was carried out, and it showed an increase in the average transmittance of the Mn3O4: Sn (0, 2, and 4 at %) from 57.6 % to 62.2 % for 700 nm and an increase of their optical band gap from 3.27 eV to 3.61 eV. We note also a decrease of their dispersive energy parameter Ed from 5.44 eV to 4.86 eV, of their static refractive index n0 from 2.02 to 1.86, as well as for their nonlinear optical parameters presented by the nonlinear refractive index n2 from 1.14 10-11 to 0.51 10-11 and the third order susceptibility χ3 from 6.14 10-13 esu to 2.49 10-13 esu. These values can be correlated to the poor crystallinity and the tensile strain of the Mn3O4: Sn (0, 2, and 4 at %) thin films, as well as to the high order of the optical bandgap energy and the decrease of the linear refractive index of these films. Hence, these thin films can be used as material for nonlinear optical applications.

Enhancing the p-type conductivity of pure phase SnO via stoichiometry control and annealing

While n-type transparent conducting oxides (TCOs) have been well developed and widely used in optoelectronic devices, the availability of high-performance p-type TCOs is still scarce which in turn hinders the further advancement of oxide based transparent optoelectronic devices. Unlike the most widely used p-type NiO, Tin monoxide (SnO) has a relatively delocalized valence band, which leads to a high hole mobility of >1 cm2/Vs. In this work, we enhance the p-type conductivity of SnO thin films by tunning the oxide stoichiometry through adjusting the growth conditions and post-growth rapid thermal annealing (RTA) treatment. Specifically, we synthesized nominally undoped Sn-rich SnO (SnO1-δ) thin films by co-sputtering an SnO target and a metallic Sn target and control the film stoichiometry by varying the sputter power of the Sn target so that SnO1-δ films with excess Sn (δ) varying from 0 to ∼5% was incorporated. We find that the addition of dilute amount of excess Sn is an effective approach to regulate the film stoichiometry so that a low p-type resistivity can be achieved after post-growth RTA. All as-grown films are amorphous and after RTA exhibit a polycrystalline tetragonal structure, with p-type resistivity decreases with increasing δ. However, metallic β-Sn clusters are formed for films with δ≳ 0.05. The presence of these β-Sn clusters results in a degraded optical transmittance by ∼10% in the visible range. With δ∼0.03 in the as-grown film, a p-type pure phase SnO film with a low resistivity of ∼0.5 Ω−cm, and a decent visible transparency of ∼60% is achieved after 300 °C RTA in N2. This p-type SnO has a wide band gap of 2.8 eV with a high valence band maximum (VBM) located in the range of 4.6–4.8 eV below the vacuum level, making it suitable for many device applications, particularly as hole transport layers in optoelectronic devices.

Effect of annealing on thin film AgInSe2 solar cell

AgInSe2 (AIS) thin films solar cell involving of n-type AgInSe2 and Si of p-type substrate by using thermal evaporation method. The influence of annealing of the preparation AgInSe2 were considered to find the best properties of solar device. Thin film AIS have been deposited under the vacuum of 1.5*10-6 Torr with (400) nm thickness at R.T and annealing temperatures (473,573) K. Polycrystalline tetragonal structure for AIS thin films from XRD and increasing of surface roughness from AFM, energy gap values decreasing with increasing annealing temperatures, all films were negative type, I-V characteristics show increasing of efficiency with increasing of annealing temperatures.

Energy transfer mechanism in Eu3+ doped tin oxide nanophosphors for red solid state lighting

A europium doped tin oxide (SnO2:Eu3+) nanophosphor is prepared by using of solution-combustion process with a variation in the doping amount of Eu3+. The results recorded by X-ray diffraction are established that SnO2: Eu3+ has a polycrystalline tetragonal structure without phase alteration for each concentration of Eu3+. The undoped SnO2 nanoparticles showed only defects related emission while emission due to the f→f transitions of Eu3+ ion is observed upon doping. The optimized photoluminescent intensity was observed for 3 mol% Eu3+. The life-time measurement of Eu3+ -doped SnO2 associated with major emission band located at 612 nm was monitored as 0.3 ms for the 3 mol% of Eu concentration. The present results reveal that Eu3+ -doped SnO2 nanoparticles may be used as a source of red light phosphor and this may be utilized for solid white light emitting application.

Structural, electrical, and optical properties of spin-coated Bi:SnO2 transparent conducting oxide thin films

We synthesized different concentrations of Bi (1, 2, 3, 4, and 5 at %) doped SnO2 (Bi:SnO2) thin films using the sol-gel spin coating method. The XRD studies confirmed that all deposited films exhibit polycrystalline tetragonal rutile structure. Raman spectra displayed three fundamental bands at 473, 631, and 774 cm−1, which correspond to the Raman modes Eg, A1g, and B2g. The average transmittance is above 76% for all films. The optical bandgap energy increased from 3.91 eV for pure SnO2 to 4.22 eV for 3 at% Bi:SnO2 film and slightly decreased for 4 and 5 at % Bi:SnO2 films. The sheet resistance (Rsh) and resistivity (ρ) values decreased up to 38.8 Ω/□ and 1.62 × 10−3 Ω-cm, respectively, in 3 at % Bi: SnO2 thin film, and then slightly increased for 4 and 5 at % Bi: SnO2 films.

The effect of replacing iron atoms instead of zinc of the quaternary compound CZTS

In this article, the quaternary compound Cu2MSnS4 was prepared in a simple and inexpensive approach, where M is the iron (Fe) and zinc (Zn) atoms by the spin coating method on a glass substrate at room temperature (RT), as a result of replacing Zn atoms by Fe. Quaternary Cu2ZnSnS4 (CZTS) and Cu2FeSrS4 (CFTS) structural and optical properties have been studied successfully. The material has been identified by X-ray diffraction, and it was discovered that CZTS has a polycrystalline Tetragonal (kesterite) structure, whereas CFTS has a Tetragonal (stannite) structure. A reduction in the full width half maximum (FWHM) of the preferred plane implies a high degree of crystallization. The structural properties of the film surface, such as grain size and roughness, were studied by Atomic force microscopy (AFM). The results explain an increase in nanoparticle size and surface roughness when Fe is substituted by Zn in the CZTS structure. The absorption coefficient values of all designed compounds in visible regions are greater than 104/cm, and the results show that the absorbance coefficient increases with Fe add. The CZTS films showed an energy gap of 1.88 eV, and this value became 1.69 eV with substituted Fe instead of Zn.

Photoluminescence in Strontium doped tin oxide thin films

The photoluminescence properties of spray pyrolyzed strontium (Sr) doped tin oxide (SnO2:Sr) thin films are presented. These transparent nano-films are found to have polycrystalline tetragonal structure. A nano-needle like grains were observed up to 1 wt% Sr doping, whereas polyhedron like grains were seen at 1.5 wt% of Sr doping. A redshift of 110 meV in the optical bandgap was obtained for SnO2:Sr(1 wt%) thin film and is attributed to defect states induced and reorientation effect caused upon Sr doping. The improvement in n-type conductivity observed for 1 wt% Sr doped tin oxide thin films is ascribed to increase in the carrier concentration and mobility. The observed increment in the intensity of visible emissions in SnO2:Sr (1 wt%) films is attributed to oxygen vacancy related recombination on Sr doping. Obtained results of SnO2:Sr are compared with those of pure SnO2 film and we find enhancement in the photoluminescence intensity when doped with Sr.

Effect of thiourea on structure, morphology and optical properties of spray deposited CZTS thin films for solar cell applications

<p>Cu2ZnSnS4 (CZTS) films of different Thiorea (SC (NH2)2) molarity were deposited by using simple chemical spray technique at substrate temperature 275°C. Analytical reagent Grade Copper chloride (CuCl2), Zinc chloride (ZnCl2), Tin chloride (SnCl4.5H2O) were used as Cu+ , Zn+ , and Sn+ ion sources respectively and thiourea (SC(NH2)2) (0.02, 0.04 0.06 0.08, and 0.1 M) was used as a Sion source. A set of five CZTS films was deposited using five different molarity of thiourea. The structure, Morphology, Elemental analysis and optical properties of these films were studied using X-ray diffratometer (XRD), Scanning Electron Microscopy (SEM) Energy Dispersive X-ray Analysis (EDX) and UV-Visible spectroscopy techniques respectively. The XRD spectra showed that all films are polycrystalline tetragonal structure with preferential orientation along (112) plane. The calculated crystallite size was increased with increase in thiourea concentration. Variations of optical band gap with thiourea molarity have been investigated using Tauc plots. SEM micrographs exhibits CZTS spherical granules regularly arranged with some void spaces. Purity of deposited films was investigated using EDX analysis. All the CZTS films exhibits higher absorption coefficient (𝛼 > 104) cm-1 and band gap in the reported range (1.2-1.53 eV) can be used as an absorber layer in solar cells.</p>

Effect of Ti doping on structural, optical and electrical properties of SnO2 transparent conducting thin films deposited by sol-gel spin coating

Abstract In the present work, various concentrations of Ti (1, 2, 3, 4 and 5 at %) doped SnO2 thin films were grown onto glass substrate using cost effective sol-gel spin coating method and subsequently investigated the effect of Ti doping concentration on structural, optical and electrical properties. X-ray diffraction studies revealed that all deposited films exhibit polycrystalline tetragonal rutile structure with fundamental orientation peak along (110) direction. Moreover, Ti doped SnO2 films were started growing along (211) direction and it was more pronounced with increasing of Ti concentration. The average grain size was decreased with the increase of Ti concentration, confirmed by XRD and AFM studies. The UV–visible spectrometer measurements shown that the average transmittance of un-doped SnO2 film was above 85%, whereas Ti doped SnO2 films were found to be a decrease of transmittance up to 77% in 5 at% Ti:SnO2 film. The optical band gap energy values were considerably decreased from 3.91 to 3.73 eV with increase of Ti content. Further, the sheet resistance (Rsh) and resistivity (ρ) values were found to be decreased with the increase of Ti doping up to 3 at % then it was slightly increased in 4 and 5 at % of Ti:SnO2 films. The efficiency parameter figure of merit (φ) was also estimated for all deposited films with the function of Ti doping.

Enhanced Magneto-Optical, Morphological, and Photocatalytic Properties of Nickel-Substituted SnO2 Nanoparticles

In this present study, pure and Ni2+ (3, 7, and 10% mol.)-substituted SnO2 nanoparticles (NPs) were synthesized by sol-gel method. The prepared samples were characterized by powder XRD, FT-IR, FE-SEM, HR-TEM, EDX, UV-visible spectra, room temperature (RT) photoluminescence (PL) spectroscopy, and VSM techniques. XRD study revealed the polycrystalline tetragonal rutile structure of pure and Ni2+-substituted SnO2 NPs. Crystallite size of pure and Ni2+-substituted SnO2 NPs were found to be 26 to 34 nm in range. FT-IR study confirmed the presence of metal-oxide (M-O) bond vibrations for pure and Ni-substituted SnO2 NPs. FE-SEM, EDX, HR-TEM, and SAED pattern indicated that pure and Ni2+-substituted SnO2 NPs are well-defined formation of spherical-sized nanocrystallites, with diameter of about 10–40 nm of grain size. UV-Vis spectrum specified a sharp absorption peak ~ 425 nm representing the band to band transition. RT-PL study showed the peak ~ 467 nm for all samples, indicating the band gap of 2.65 eV. The higher value of Ms is found to be 0.0429 emu/g for Ni-substituted SnO2 NPs. Magnetic study revealed that the Ni-substituted SnO2 NPs presented ferromagnetism. Photocatalytic degradation (PCD) of methylene blue (MB) was analyzed using photo-catalytic reactor and obtained the maximum of PCD efficiency of 3% Ni-substituted SnO2 NPs under the visible light irradiation.

TiO2 thin films: Impact of substrate temperature on structural and morphological properties

Smooth and white spherical shaped TiO2 thin films are successfully deposited by Nebulizer Spray Pyrolysis (NSP) technique. The TiO2 thin films are characterized by XRD, SEM, DRS, PL and I-V analysis. Anatase phase polycrystalline tetragonal structure with preferential orientation along (1 0 1) direction obtained form XRD. The expansion and contraction of Ti-O bonds leads to a high crystalline nature with its purity at 289 nm. The absorbance increases with substrate temperature due to the decrease of film thickness, packing density and shrinkage of spray droplets. TiO2 thin films indicate that the film is made up of small granules having slab like particles with some voids at lower temperature. The tiny particles are combined together to form white spherical shaped flower particles with pinholes at 450oC. A room temperature resistivity of the film deposited at 400oC is found to be in the order of 105 Ω/cm, which decreases to 103 Ω/cm for the films prepared at 450oC.

Role of annealing temperature on the properties of SrO nanoparticles by precipitation method

Strontia nanoparticles are successfully prepared by chemical precipitation method. The SrO nanoparticles are characterized by XRD, UV-DRS and I-V analysis. X-ray diffraction peaks reveal the single-phase polycrystalline tetragonal structure with preferential orientation along (2 0 2) direction. Influence of annealing temperature strongly induce the growth of peak which indicates the increased intensity of (202) peak. The heat treatment strongly distresses the growth of triplet peaks (002), (101) and (110) whereas the same augment the growth of (202) and (310). Strontium oxide nanoparticles would allow more light for absorption in UV region due to its rough surface whereas the same would allow moderate light absorption in visible region due to its high packing density. The expansion and contraction of Sr-O bonds leads to a high crystalline nature with its purity at 322 nm. It is proposed that strain and surface defects in SrO nanocrystal take place due to different absorption edge.

Effect of evaporation behavior of zinc tin phosphide alloys on the composition, structure, and photoconductive properties of their thin films

The evaporation behavior of zinc tin phosphide (ZTP) alloys and its effect on the composition, structure, and photoconductive properties of the deposited films were investigated. ZTP alloys were prepared, and they were found to be of ZnSn-phosphide composition and chalcopyrite structure as obtained by thermogravimetric and x-ray diffraction analysis. The evaporation of the alloys produced random and inhomogeneous deposition with unevaporated residues due to the large difference in vapor pressure, particularly, between Zn and Sn. A closed spaced vapor deposition type setup favored uniform deposition of the films, however, with a dramatic deviation of composition and structure from that of the alloys. Rutherford backscattering, x-ray photoelectron, and energy dispersive spectroscopic studies revealed that the composition of the films is close to ZnP2 stoichiometry with less than 2% of Sn content. Raman spectroscopy and transmission electron microscopy studies showed that the films are of polycrystalline tetragonal ZnP2 structure and evolve to monocrystalline on electron irradiation. The films exhibited a broad band photoresponse in the visible wavelength region with high responsivity to the red light. The study establishes the effect of evaporation behavior of materials with large difference in vapor pressure on the properties and activity of the deposited films thereof.

Effect of gadolinium on tin oxide thin films prepared by nebulizer spray pyrolysis method

Gadolinium-doped tin oxide (SnO2: Gd) thin films were prepared by the nebulizer spray pyrolysis technique on glass substrates using tin (IV) chloride pentahydrate (SnCl2·5H2O) and Gadolinium Sulphate Octahydrate as source materials. Different wt % of doping such as (0%, 1%, 2% and 3%) Gadolinium was used to prepare the spray solution, and their effects on structural, morphological, optical, properties were investigated. X-ray diffraction patterns revealed the polycrystalline tetragonal structure of prepared films. The crystallite size value varies due to Gd doing level. SEM images demonstrated well-aligned tetragonal-shaped nano-grains. Optical band gap values were estimated to be in the range of 3.78–3.82 ​eV by Tauc’s plot. The effects of Gd doping level on the SnO2 thin films obtained using an excitation wavelength of 350 ​nm exhibit emission peaks centered at 361 ​nm, 496 ​nm, 520 ​nm, 540 ​nm and 594 ​nm respectively. It’s indicated that SnO2 thin films exhibited a broad dominant peak near 396 ​nm (about 3.14 ​eV). Raman spectroscopy indicates the spectra for as deposited SnO2 is dominated by presence of strong and sharp peak at 2434 ​cm−1 along with the peak of smaller intensity at 482 ​cm−1.