Chemical synthesis of nanocrystalline SnO2 thin films for supercapacitor application

Nanocrystalline SnO₂ thin films were deposited by simple and inexpensive chemical route. The films were characterized for their structural, morphological, wettability and electrochemical properties using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy techniques (SEM), transmission electron microscopy (TEM), contact angle measurement, and cyclic voltammetry techniques. The XRD study revealed the deposited films were nanocrystalline with tetragonal rutile structure of SnO₂. The FT-IR studies confirmed the formation of SnO₂ with the characteristic vibrational mode of Sn-O. The SEM studies showed formation of loosely connected agglomerates with average size of 5-10 nm as observed from TEM studies. The surface wettability showed the hydrophilic nature of SnO₂ thin film (water contact angle 9°). The SnO₂ showed a maximum specific capacitance of 66 F g⁻¹ in 0.5 Na₂SO₄ electrolyte at 10 mV s⁻¹ scan rate.     

Electrodeposition and growth mechanism of SnSe thin films

Tin selenide (SnSe) thin films were electrochemically deposited onto Au(1 1 1) substrates from an aqueous solution containing SnCl₂, Na₂SeO₃, and EDTA at room temperature (25 °C). The electrochemical behaviors and the codeposition potentials of Sn and Se were explored by cyclic voltammetry. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and UV-vis absorption spectroscopy were employed to characterize the thin films. When the electrodeposition potential increased, the Se content in the films decreased. It was found that the stoichiometric SnSe thin films could be obtained at −0.50 V. The as-deposited films were crystallized in the preferential orientation along the (1 1 1) plane. The morphologies of SnSe films could be changed from spherical grains to platelet-like particles as the deposition potential increases. The SEM investigations show that the film growth proceeds via nucleation, growth of film layer and formation of needle-like particles on the overlayer of the film. The optical absorption study showed the film has direct transition with band gap energy of 1.3 eV.     

Electrosynthesis and characterization of CdSe thin films: Optimization of preparative parameters by photoelectrochemical technique

CdSe thin films have been electrodeposited potentiostatically onto stainless-steel and fluorine-doped tin oxide-coated glass substrates from an aqueous acidic bath using cadmium acetate ((CH₃COO)₂Cd·2H₂O) as a Cd ion source. Preparative parameters such as deposition potential, solution concentration, bath temperature, pH of the electrolytic bath and deposition time have been optimized by using photoelectrochemical (PEC) technique to obtain well adherent and uniform thin films. The electrodeposits were dark brown in colour. The films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical absorption techniques. XRD studies reveal that films are polycrystalline, with hexagonal crystal structure. SEM shows that the films are compact, with spherical grains. Optical absorption studies reveal that the material exhibits a direct optical transition having band gap energy ∼1.72 eV. PEC study shows that the films are photoactive.     

Structural and optical properties of electrodeposited molybdenum oxide thin films

Electrosynthesis of Mo(IV) oxide thin films on F-doped SnO₂ conducting glass (10-20/Ω/□) substrates were carried from aqueous alkaline solution of ammonium molybdate at room temperature. The physical characterization of as-deposited films carried by thermogravimetric/differential thermogravimetric analysis (TGA/DTA), infrared spectroscopy and X-ray diffraction (XRD) showed the formation of hydrous and amorphous MoO₂. Scanning electron microscopy (SEM) revealed a smooth but cracked surface with multi-layered growth. Annealing of these films in dry argon at 450 °C for 1 h resulted into polycrystalline MoO₂ with crystallites aligned perpendicular to the substrate. Optical absorption study indicated a direct band gap of 2.83 eV. The band gap variation consistent with Moss rule and band gap narrowing upon crystallization was observed.Structure tailoring of as-deposited thin films by thermal oxidation in ambient air to obtain electrochromic Mo(VI) oxide thin films was exploited for the first time by this novel route. The results of this study will be reported elsewhere.     

Room temperature chemical synthesis of lead selenide thin films with preferred orientation

Room temperature chemical synthesis of PbSe thin films was carried out from aqueous ammoniacal solution using Pb(CH₃COO)₂ as Pb²⁺ and Na₂SeSO₃ as Se²⁻ ion sources. The films were characterized by a various techniques including, X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), Fast Fourier transform (FFT) and UV-vis-NIR techniques. The study revealed that the PbSe thin film consists of preferentially oriented nanocubes with energy band gap of 0.5 eV.     

Preparation and characterization of electrodeposited Sb2Se3 thin films from non-aqueous media

Semiconducting Sb₂Se₃ thin films have been prepared onto the stainless steel and fluorine doped tin oxide coated glass substrates from non-aqueous media using an electrodeposition technique. The electrodeposition potentials for different bath compositions and concentrations of solution have been estimated from the polarization curves. SbCl₃ and SeO₂ in the volumetric proportion as 1:1 with their equimolar solution concentration of 0.05 M form good quality films. The films are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and optical absorption techniques. The SEM studies show that the film covers the total substrate surface with uneven surface morphology. The XRD patterns of the films obtained by varying compositions and concentrations show that the as-deposited films are polycrystalline with relatively higher grain size for 1:1 composition and 0.05 M concentration. The optical band gap energy for indirect transition in Sb₂Se₃ thin films is found to be 1.195 eV.     

A novel chemical synthesis and characterization of Mn3O4 thin films for supercapacitor application

Mn₃O₄ thin films have been prepared by novel chemical successive ionic layer adsorption and reaction (SILAR) method. Further these films were characterized for their structural, morphological and optical properties by means of X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), field emission scanning electron microscopy (FESEM), wettability test and optical absorption studies. The XRD pattern showed that the Mn₃O₄ films exhibit tetragonal hausmannite structure. Formation of manganese oxide compound was confirmed from FTIR studies. The optical absorption showed existence of direct optical band gap of energy 2.30 eV. Mn₃O₄ film surface showed hydrophilic nature with water contact angle of 55°. The supercapacitive properties of Mn₃O₄ thin film investigated in 1 M Na₂SO₄ electrolyte showed maximum supercapacitance of 314 F g⁻¹ at scan rate 5 mV s⁻¹.     

Supercapacitive cobalt oxide (Co3O4) thin films by spray pyrolysis

Uniform and adherent cobalt oxide thin films have been deposited on glass substrates from aqueous cobalt chloride solution, using the solution spray pyrolysis technique. Their structural, optical and electrical properties were investigated by means of X-ray diffraction (XRD), scanning electron micrograph (SEM), optical absorption and electrical resistivity measurements. Along with this, to propose Co₃O₄ for possible application in energy storage devices, its electrochemical supercapacitor properties have been studied in aqueous KOH electrolyte. The structural analysis from XRD pattern showed the oriented growth of Co₃O₄ of cubic structure. The surface morphological studies from scanning electron micrographs revealed the nanocrystalline grains alongwith some overgrown clusters of cobalt oxide. The optical studies showed direct and indirect band gaps of 2.10 and 1.60 eV, respectively. The electrical resistivity measurement of cobalt oxide films depicted a semiconducting behavior with the room temperature electrical resistivity of the order of 1.5 × 10³ Ω cm. The supercapacitor properties depicted that spray-deposited Co₃O₄ film is capable of exhibiting specific capacitance of 74 F/g.     

BaMoO4 powders processed in domestic microwave-hydrothermal: Synthesis, characterization and photoluminescence at room temperature

In this paper, BaMoO₄ powders were prepared by the coprecipitation method and processed in a domestic microwave-hydrothermal. The obtained powders were characterized by X-ray diffraction (XRD), Fourier transform Raman (FT-Raman) spectroscopy, ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements. The morphology of these powders were investigated by scanning electron microscopy (SEM). SEM micrographs showed that the BaMoO₄ powders present a polydisperse particle size distribution. XRD and FT-Raman analyses revealed that the BaMoO₄ powders are free of secondary phases and crystallize in a tetragonal structure. UV-vis was employed to determine the optical band gap of this material. PL measurements at room temperature exhibited a maximum emission around 542 nm (green emission) when excited with 488 nm wavelength. This PL behavior was attributed to the existence of intrinsic distortions into the [MoO₄] tetrahedron groups in the lattice.     

Effect of RF power and sputtering pressure on the structural and optical properties of TiO2 thin films prepared by RF magnetron sputtering

TiO₂ thin films were deposited onto quartz substrates by RF magnetron sputtering. The samples deposited at various RF powers and sputtering pressures and post annealed at 873 K, were characterized using X-ray diffraction (XRD), micro Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-vis spectroscopy and photoluminescence (PL) spectroscopy. XRD spectrum indicates that the films are amorphous-like in nature. But micro-Raman analysis shows the presence of anatase phase in all the samples. At low sputtering pressure, increase in RF power favors the formation of rutile phase. Presence of oxygen defects, which can contribute to PL emission is evident in the XPS studies. Surface morphology is much affected by changes in sputtering pressure which is evident in the SEM images. A decrease in optical band gap from 3.65 to 3.58 eV is observed with increase in RF power whereas increase in sputtering pressure results in an increase in optical band gap from 3.58 to 3.75 eV. The blue shift of absorption edge in all the samples compared to that of solid anatase is attributed to quantum size effect. The very low value of extinction coefficient in the range 0.0544-0.1049 indicates the excellent optical quality of the samples. PL spectra of the films showed emissions in the UV and visible regions.     

A simple and low temperature process for super-hydrophilic rutile TiO2 thin films growth

We investigate an environmentally friendly aqueous solution system for rutile TiO₂ violet color nanocrystalline thin films growth on ITO substrate at room temperature. Film shows considerable absorption in visible region with excitonic maxima at 434 nm. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), UV-vis, water surface contact angle and energy dispersive X-ray analysis (EDX) techniques in addition to actual photo-image that shows purely rutile phase of TiO₂ with violet color, super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 3.15 ± 0.4 nm, characterize the films. Band gap energy of 4.61 eV for direct transition was obtained for the rutile TiO₂ films. Film surface shows super-hydrophilic behavior, as exhibited water contact angle was 7°. Strong visible absorption (not due to chlorine) leaves future challenge to use these films in extremely thin absorber (ETA) solar cells.     

Novel chemical synthetic route and characterization of zinc selenide thin films

Zinc selenide (ZnSe) thin film have been deposited using chemical bath method on non-conducting glass substrate in a tartarate bath containing zinc sulfate, ammonia, hydrazine hydrate, sodium selenosulfate in an aqueous alkaline medium at 333 K. The deposition parameter of the ZnSe thin film is interpreted in the present investigation. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption, electrical measurements, atomic absorption spectroscopy (AAS). The ZnSe thin layers grown with polycrystalline zinc blende system along with some amorphous phase present in ZnSe film. The direct optical band gap ‘E_g’ for the film was found to be 2.81 eV and electrical conductivity in the order of 10⁻⁸(Ω cm)⁻¹ with n-type conduction mechanism.     

Effects of thermal oxidation temperature on vacuum evaporated tin dioxide film

In order to investigate the effect of thermal oxidation temperature on tin dioxide (SnO₂), tin dioxide films were obtained on quartz substrates by vacuum evaporation of tin metal. The films were characterized by X-ray diffraction (XRD) analyses, scanning electron microscopy (SEM), temperature dependent electrical resistivity measurement and optical absorption spectroscopy. The SEM images showed that the films are dense, continuous and are composed of nanoparticles and particle sizes are increased after thermal oxidation. From the X-ray measurement results, the films indicated two strong reflection peaks of tetragonal structure in the orientations of (1 0 1) and (2 0 0) at 2θ = 33.89° and 37.95°, respectively. Intensity of the peaks increased with increasing thermal oxidation temperature. We found resistivity values of about 10⁻⁴ Ω-cm. Optical absorption spectra of the films in the UV–Vis spectral range revealed that optical band gap (E_g) value of the films increases with increasing thermal oxidation temperature.     

Nd:YAG laser synthesis of nanostructural V2O5 from vanadium oxide sols: Morphological and structural characterizations

Vanadium oxide thin films were prepared by sol-gel method, then subjected to Nd:YAG laser (CW, 1064 nm) radiation. The characteristics of the films were changed by varying the intensity of the laser radiation. The nanocrystalline films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). XRD revealed that above 102 W/cm² the original xerogel structure disappears and above 129 W/cm² the films become totally polycrystalline with an orthorhombic structure. From TEM observations, we can see that due to laser radiation, the originally fibrillar-like particles disappear and irregular shaped, layer structured V₂O₅ particles are created. From XPS spectra we can conclude that due to laser radiation the O/V ratio increased with higher intensities.     

Synthesis, characterization of chemically deposited indium selenide thin films at room temperature

Polycrystalline In₂Se₃ semiconducting thin films were prepared by using relatively simple chemical bath deposition method at room temperature by the reaction between indium chloride, tartaric acid, hydrazine hydrate and sodium selenosulphate in an aqueous alkaline medium. Various preparative conditions of thin film deposition are outlined. The as grown films were found to be transparent, uniform, well adherent and red in color. The films were characterized using X-ray diffraction (XRD), scanning electron microscopy, atomic absorption spectroscopy and energy dispersive atomic X-ray diffraction (EDAX). The XRD analysis of the film showed the presence of polycrystalline nature with hexagonal crystal structure. SEM study revels that the grains are homogenous, without cracks or pinholes and well covers the glass substrate. The optical absorption and electrical conductivity was measured. The direct optical band gap value for the films was found to be of the order of 2.35 eV at room temperature and have specific electrical conductivity of the order of 10⁻² (Ω cm)⁻¹ showing n-type conduction mechanism. The utility of the adapted technique is discussed from the view-point of applications considering the optoelectric and structural data.     

Synthesis and characterization of GaN nanowires by ammoniating Ga2O3/Cr thin films deposited on Si(1 1 1) substrates

GaN nanowires have been successfully synthesized on Si(1 1 1) substrates by magnetron sputtering through ammoniating Ga₂O₃/Cr thin films at 950 °C. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), FT-IR spectrophotometer, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM), and photoluminescence (PL) spectrum were carried out to characterize the microstructure, morphology, and optical properties of GaN samples. The results demonstrate that the nanowires are single-crystal GaN with hexagonal wurtzite structure and high-quality crystalline, have the size of 30-80 nm in diameter and several tens of microns in length with good emission properties. The growth direction of GaN nanowires is perpendicular to the fringe of (1 0 1) plane. The growth mechanism of GaN nanowires is also discussed in detail.     

Effect of Fe3+ doping on structural,optical and electrical properties δ-Bi2O3 thin films

Fe³⁺ doped δ-Bi₂O₃ thin films were prepared by sol–gel method on quartz glass substrate at room temperature and annealed at 800 °C. The thin films were then characterized for structural, surface morphological, optical and electrical properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption measurements and d.c. two-probe, respectively. The XRD analyses revealed the formation δ-Bi₂O₃ followed by a mixture of Bi₂₅FeO₄₀ and Bi₂Fe₄O₉. SEM images showed reduction in grain sizes after doping and the optical studies showed a direct band gap which reduced from 2.39 eV for pure δ-Bi₂O₃ to 1.9 eV for 10% Fe³⁺ doped δ-Bi₂O₃ thin film. The electrical conductivity measurement showed the films are semiconductors.     

Role of Cr ions on superexchange coupling in α-Fe2O3 nanoparticles

Synthesis of nanocomposites of iron oxide & chromium oxide (α-Fe₂O₃–Cr₂O₃) with different concentrations was carried out by a wet-chemical method and the structural, optical and hyperfine properties have been investigated. The prepared nanocomposites were characterized by powder X-ray diffractometry (PXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV–VIS spectroscopy, Fourier transformed infrared (FTIR) spectroscopy and Mössbauer spectroscopy. XRD measurements confirmed the formation of pure phase composites having particle sizes in nanometer regime. The same has been corroborated by TEM micrographs, which revealed that the formation of monodispersed nanocomposites have the average particle size 44 nm. Mössbauer study of the samples showed the transition of iron oxide from anti-ferromagnetic state to paramagnetic state having a typical relaxation in the spectrum with increasing concentration of Cr₂O₃.     

Preparation and luminescent characteristic of Li3NbO4 nanophosphor

Synthesis and luminescence properties of Li₃NbO₄ oxides by the sol-gel process were investigated. The products were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and absorption spectra. The PL spectra excited at 247 nm have a broad and strong blue emission band maximum at 376 nm, corresponding to the self-activated luminescence of the niobate octahedra group [NbO₆]⁷⁻. The optical absorption spectra of the samples sintered at temperatures of 600 and 700 °C exhibited the band-gap energies of 4.0 and 4.08 eV.     

The growth mechanism and supercapacitor study of anodically deposited amorphous ruthenium oxide films

In the present study, ruthenium oxide (RuO₂) thin films were deposited on the stainless steel (s.s.) substrates by anodic deposition. The nucleation and growth mechanism of electrodeposited RuO₂ film has been studied by cyclic voltammetry (CV) and chronoamperometry (CA). The deposited films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive analysis by X-rays (EDAX) for structural, morphological, and compositional studies. The electrochemical supercapacitor study of ruthenium oxide thin films have been carried out for different film thicknesses in 0.5 M H₂SO₄ electrolyte. The highest specific capacitance was found to be 1190 F/g for 0.376 mg/cm² film thickness.