Preparation and properties of spray-deposited ZnIn2Se4 nanocrystalline thin films

Zinc indium selenide (ZnIn₂Se₄) thin films have been deposited onto amorphous and fluorine doped tin oxide (FTO)-coated glass substrates using a spray pyrolysis technique. Aqueous solution containing precursors of Zn, In, and Se has been used to obtain good quality deposits at different substrate temperatures. The preparative parameters such as substrate temperature and concentration of precursors solution have been optimized by photoelectrochemical technique and are found to be 325 °C and 0.025 M, respectively. The X-ray diffraction patterns show that the films are nanocrystalline with rhombohedral crystal structure having lattice parameter a=4.05 Å. The scanning electron microscopy (SEM) studies reveal the compact morphology with large number of single crystals on the surface. From optical absorption data the indirect band gap energy of ZnIn₂Se₄ thin film is found to be 1.41 eV.     

Structural and optical properties of In35Sb45Se20−xTex phase-change thin films

Physical properties of In₃₅Sb₄₅Se_20−xTe_x thin films with different compositions (x=2.5, 5, 7.5, 10, 12.5 and 15 at %) prepared by electron beam evaporation method are studied. X-ray diffraction results indicate that the as-evaporated films depend on the Te content and the crystallized compounds consist mainly of Sb₂Se₃ with small amount of Sb₂SeTe₂. Transmittance and reflectance of the films are found to be thickness dependent. Optical-absorption data indicate that the absorption mechanism is direct transition. Optical band gap values decrease with increase in Te content as well as with increase in film thickness.     

Effect of composition and thermal annealing on the absorption and electrical conduction of Se85−xTe15Sbx glasses

The optical absorption of the as-prepared and thermally annealed Se_85−xTe₁₅Sb_x (0≤x≤9) thin films was measured. The mechanism of the optical absorption follows the rule of non-direct transition. The optical energy gap (E₀) decreased from 1.12 to 0.84 eV with increasing Sb content of the as-prepared films from 0 to 9 at.%. The as-prepared Se₇₆Te₁₅Sb₉ films showed an increase in (E₀) with increasing the temperature of annealing in the range above T_g (363 K). The electrical conductivity of the as-prepared and annealed films was found to be of Arrhenius type with temperature in the range 300-360 K. The activation energy for conduction was found to decrease with increasing both the Sb content and temperature of annealing. The results were discussed on the basis of the lone-pair electron effect and of amorphous crystalline transformation.     

Effect of heat treatment on the optical and electrical transport properties of Ge15Sb10Se75 and Ge25Sb10Se65 thin films

The effect of heat treatment on the optical and electrical properties of Ge₁₅Sb₁₀Se₇₅ and Ge₂₅Sb₁₀Se₆₅ thin films in the range of annealing temperature 373-723 K has been investigated. Analysis of the optical absorption data indicates that Tauc's relation for the allowed non-direct transition successfully describes the optical processes in these films. The optical band gap (E_g^opt.) as well as the activation energy for the electrical conduction (ΔE) increase with the increase of annealing temperature (T_a) up to the glass transition temperature (T_g). Then a remarkable decrease in both the E_g^opt. and ΔE values occurred with a further increase of the annealing temperature (T_a>T_g). The obtained results were explained in terms of the Mott and Davis model for amorphous materials and amorphous to crystalline structure transformations. Furthermore, the deduced value of E_g^opt. for the Ge₂₅Sb₁₀Se₆₅ thin film is higher than that observed for the Ge₁₅Sb₁₀Se₇₅ thin film. This behavior was discussed on the basis of the chemical ordered network model (CONM) and the average value for the overall mean bond energy 〈E〉 of the amorphous system Ge_xSb₁₀Se_90−x with x=15 and 25 at%. The annealing process at T_a>T_g results in the formation of some crystalline phases GeSe, GeSe₂ and Sb₂Se₃ as revealed in XRD patterns, which confirms our discussion of the obtained results.     

Optical and thermoelectric characterizations of electroplated n-Bi2(Te0.9Se0.1)3

Bismuth selenotelluride (Bi₂(Te_0.9Se_0.1)₃) films were electrodeposited at constant current density from acidic aqueous solutions with Arabic gum in order to produce thin films for miniaturized thermoelectric devices. X-ray fluorescence spectroscopy determined film compositions. X-ray diffraction pattern shows that the films as deposited are polycrystalline, isostructural to Bi₂Te₃ and covered by crystallites. Mueller-matrix analysis reveals that the electroplated layers are optically like an isotropic medium. Their pseudo-dielectric functions were determined using mid-infrared spectroscopic ellipsometry. Tauc-Lorentz combined with Drude dispersion relations were successfully used. The energy band gap E_g was found to be about 0.15 eV. Moreover, the fundamental absorption edge was described by an indirect optical band-to-band transition. From Seebeck coefficient measurement, films exhibit n-type charge carrier and the value of thermoelectric power is about −40 μV/K.     

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.     

Structural studies and physical properties of novel Sm-doped Sb2Se3 nanorods

Sm³⁺ doped Sb₂Se₃ nanorods were synthesized by the co-reduction method at 180 °C and pH=12 for 48 h. Powder XRD patterns indicate that the Sm_xSb_2−xSe₃ crystals (x=0.00-0.05) are isostructural with Sb₂Se₃. The cell parameters increase for Sm³⁺ upon increasing the dopant content (x). SEM images show that doping of Sm³⁺ ions in the lattice of Sb₂Se₃ results in nanorods. High-resolution transmission electron microscopic (HRTEM) studies reveal that the Sm_0.05Sb_1.95Se₃ is oriented in the [1 0 −1] growth direction. UV-vis absorption reveals mainly electronic transitions of the Sm³⁺ ions in doped nanomaterials. Emission spectra of doped materials, in addition to the characteristic red emission peaks of Sb₂Se₃, show other emission bands originating from f-f transitions of the Sm³⁺ ions. The electrical conductance of Sm-doped Sb₂Se₃ is higher than undoped Sb₂Se₃ and increase with temperature.     

Electrodeposition of n-type Bi2Te3−ySey thermoelectric thin films on stainless steel and gold substrates

Thermoelectric films of n-Bi₂Te_3−ySe_y were prepared by potentiostatic electrodeposition technique onto stainless steel and gold substrates at room temperature. These films were used for morphological, compositional and structural analysis by environment scanning electron microscope (ESEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The effect of different substrates on the structure and morphology of Bi₂Te_3−ySe_y films and relation between Se content in the electrodepositing solutions and in the films were also investigated. These studies revealed that Bi, Te and Se could be co-deposited to form Bi₂Te_3−ySe_y semiconductor compound in the solution containing Bi³⁺, HTeO₂⁺ and H₂SeO₃. The morphology and structure of the films are sensitive to the substrate material. The doped content of Se element in the Bi₂Te_3−ySe_y compound can be controlled by adjusting the Se⁴⁺ concentration in the electrodepositing solution. X-ray diffraction analysis indicates that the films prepared at −40 mV versus saturated calomel electrode (SCE) exhibit strong (1 1 0) orientation with rhombohedral structure.     

Growth of highly-oriented CaCu3Ti4O12 thin films on SrTiO3 (1 0 0) substrates by a chemical solution route

Highly-oriented CaCu₃Ti₄O₁₂ (CCTO) thin films deposited directly on SrTiO₃ (1 0 0) substrates have been developed successfully using a chemical solution coating method. X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were employed to characterize the structure and the morphology. It was observed that the CCTO thin films had the 1 μm × 1 μm domain-like microstructure that consists of compact grains of about 0.1 μm in size. The cross sectional SEM image shows that the CCTO grains grow regularly close to the clear interface between the CCTO film and the SrTiO₃ substrate. The result was discussed in terms of lattice mismatch between CCTO and SrTiO₃.     

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.     

Chemical synthesis of nano-porous ruthenium oxide (RuO2) thin films for supercapacitor application

Ruthenium oxide (RuO₂) thin films have been prepared using single step chemical method containing Ru(III) Cl₃ solution in an aqueous medium at low temperature. The structural, morphological and optical properties have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical absorption technique. The XRD study revealed the formation of amorphous RuO₂ thin film. The surface examination by SEM showed formation of nano-porous material on the substrate. The TEM study revealed the formation of nanostructured material. The optical absorption studies showed the presence of direct band transition with band gap equal to 2.2 eV. The RuO₂ has proved its applicability in supercapacitor showing 50 F/g specific capacitance in 0.5 M H₂SO₄ at 20 mV/s scan rate.     

Magnetic and transport properties of Mn-doped Bi2Se3 and Sb2Se3

We report on the single crystal growth and thermoelectric and magnetic properties of Mn-doped Bi₂Se₃ and Sb₂Se₃ single crystals prepared by the temperature gradient solidification method. The composition and crystal structure were determined using electron probe microanalysis and θ–2θ powder X-ray diffraction studies, respectively. The lattice constants of several percent Mn-doped Bi₂Se₃ and Sb₂Se₃ were slightly smaller than those of the undoped sample due to the smaller Mn atomic radius (1.40 Å) than those of Bi (1.60 Å) and Sb (1.45 Å). Mn-doped Bi₂Se₃ and Sb₂Se₃ showed spin-glass and paramagnetic properties, respectively.     

A comparative study of the physical properties of Sb2S3 thin films treated with N2 AC plasma and thermal annealing in N2

As-deposited antimony sulfide thin films prepared by chemical bath deposition were treated with nitrogen AC plasma and thermal annealing in nitrogen atmosphere. The as-deposited, plasma treated, and thermally annealed antimony sulfide thin films have been characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy, scanning electron microscopy, atomic force microscopy, UV-vis spectroscopy, and electrical measurements. The results have shown that post-deposition treatments modify the crystalline structure, the morphology, and the optoelectronic properties of Sb₂S₃ thin films. X-ray diffraction studies showed that the crystallinity of the films was improved in both cases. Atomic force microscopy studies showed that the change in the film morphology depends on the post-deposition treatment used. Optical emission spectroscopy (OES) analysis revealed the plasma etching on the surface of the film, this fact was corroborated by the energy dispersive X-ray spectroscopy analysis. The optical band gap of the films (E_g) decreased after post-deposition treatments (from 2.36 to 1.75 eV) due to the improvement in the grain sizes. The electrical resistivity of the Sb₂S₃ thin films decreased from 10⁸ to 10⁶ Ω-cm after plasma treatments.     

Third-order nonlinear optical properties of Bi2S3 and Sb2S3 nanorods studied by the Z-scan technique

Bismuth sulfide (Bi₂S₃) and antimony sulfide (Sb₂S₃) nanorods were synthesized by hydrothermal method. The products were characterized by UV-vis spectrophotometer, X-ray powder diffraction (XRD) and transmission electron microscope (TEM). Bi₂S₃ and Sb₂S₃ nanorods were measured by Z-scan technique to investigate the third-order nonlinear optical (NLO) properties. The result of NLO measurements shows that the Bi₂S₃ and Sb₂S₃ nanorods have the behaviors of the third-order NLO properties of both NLO absorption and NLO refraction with self-focusing effects. The third-order NLO coefficient χ⁽³⁾ of the Bi₂S₃ and Sb₂S₃ nanorods are 6.25×10⁻¹¹ esu and 4.55×10⁻¹¹ esu, respectively. The Sb₂S₃ and Bi₂S₃ nanorods with large third-order NLO coefficient are promising materials for applications in optical devices.     

On the structure, morphology, and optical properties of chemical bath deposited Sb2S3 thin films

In the present paper, we have reported the room temperature growth of antimony sulphide (Sb₂S₃) thin films by chemical bath deposition and detailed characterization of these films. The films were deposited from a chemical bath containing SbCl₃ and Na₂S₂O₃ at 27 °C. We have analysed the structure, morphology, composition and optical properties of as deposited Sb₂S₃ films as well as those subjected to annealing in nitrogen atmosphere or in air. As-deposited films are amorphous to X-ray diffraction (XRD). However, the diffused rings in the electron diffraction pattern revealed the existence of nanocrystalline grains in these films. XRD analysis showed that upon annealing in nitrogen atmosphere these films transformed into polycrystalline with orthorhombic structure. Also, we have observed that during heating in air, Sb₂S₃ first converts into orthorhombic form and then further heating results in the formation of Sb₂O₃ crystallites. Optical bandgap energy of as deposited and annealed films was evaluated from UV-vis absorption spectra. The values obtained were 2.57 and 1.73 eV for the as-deposited and the annealed films respectively.     

Derivation of the optical constants of spin coated CeO2-TiO2-ZrO2 thin films prepared by sol-gel route

Ternary thin films of cerium titanium zirconium mixed oxide were prepared by the sol-gel process and deposited by a spin coating technique at different spin speeds (1000-4000 rpm). Ceric ammonium nitrate, Ce(NO₃)₆(NH₄)₂, titanium butoxide, Ti[O(CH₂)₃CH₃]₄, and zirconium propoxide, Zr(OCH₂CH₂CH₃)₄, were used as starting materials. Differential calorimetric analysis (DSC) and thermogravimetric analysis (TGA) were carried out on the CeO₂-TiO₂-ZrO₂ gel to study the decomposition and phase transition of the gel. For molecular, structural, elemental, and morphological characterization of the films, Fourier Transform Infrared (FTIR) spectral analysis, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), cross-sectional scanning electron microscopy (SEM), and atomic force microscopy (AFM) were carried out. All the ternary oxide thin films were amorphous. The optical constants (refractive index, extinction coefficient, band gap) and thickness of the films were determined in the 350-1000 nm wavelength range by using an nkd spectrophotometer. The refractive index, extinction coefficient, and thickness of the films were changed by varying the spin speed. The oscillator and dispersion energies were obtained using the Wemple-DiDomenico dispersion relationship. The optical band gap is independent of the spin speed and has a value of about E_g≈2.82±0.04 eV for indirect transition.     

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.     

Characterization of a thin CeO2-ZrO2-Y2O3 films electrochemical deposited on stainless steel

In this paper, we report for the first time formation of a thin CeO₂-ZrO₂-Y₂O₃ films electrodeposited on a stainless steel substrate. The samples have been characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The XRD and XPS data indicate formation of a solid solution and additional existence of Ce³⁺ states near the surface. After annealing, SEM examination has shown a microstructure formed by dispersed spherical agglomerates having a size between 20 and 60 nm.     

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.     

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.