Nanocrystalline copper selenide thin films by chemical spray pyrolysis

Thin films of copper selenide were deposited onto amorphous glass substrates at various substrate temperatures by computerized spray pyrolysis technique. The as deposited copper selenide thin films were used to study a wide range of characteristics including structural, surface morphological, optical and electrical, Hall Effect and thermo-electrical properties. X-ray diffraction study reveals that the films are polycrystalline in nature with hexagonal (mineral klockmannite) crystal structure irrespective of the substrate temperature. The crystalline size is found to be in the range of 23–28 nm. The SEM study reveals that the grains are uniform with uneven spherically shaped and spread over the entire surface of the substrates. EDAX analysis confirmed the nearly stoichiometric deposition of the film at 350 °C. The direct band gap values are found to be in the range 2.29–2.36 eV depending on the substrate temperature. The Hall Effect study reveals that the films exhibit p-type conductivity. The values of carrier concentration and mobility for the film are found to be 5.02 × 10¹⁷ cm^?3 and 5.19 × 10^?3 cm² V^?1 s^?1; respectively for film deposited at 350 °C.     

Characterization of Tin disulphide thin films prepared at different substrate temperature using spray pyrolysis technique

Thin films of tin disulphide on glass substrates were prepared by spray pyrolysis technique using precursor solutions of SnCl₂·2H₂O and n–n dimethyl thiourea at different substrate temperatures varied in the range 348–423 K. Using the hot probe technique the type of conductivity is found to be n type. X ray diffraction analysis revealed the polycrystalline nature with increasing crystallinity with respect to substrate temperature. The preferential orientation growth of SnS₂ compound having hexagonal structure along (002) plane increased with the substrate temperature. The size of the tin disulphide crystallites with nano dimension were determined using the Full Width Half Maximum values of the Bragg peaks and found to increase with the substrate temperature. The surface morphology had been observed on the surface of these films using scanning electron microscope. The optical absorption and transmittance spectra have been recorded for these films in the wavelength range 400–800 nm. Thickness of these films was found using surface roughness profilometer. The absorption coefficient (α) was determined for all the films. Direct band gap values were found to exist in all the films deposited at different substrate temperatures. The value of room temperature resistivity in dark decreased from 5.95 × 10³ Ω cm for the amorphous film deposited at low temperature (348 K) to 2.22 × 10³ Ω cm for the polycrystalline film deposited at high temperature (423 K) whereas the resistivity values in light decreased from 1.48 × 10³ to 0.55 × 10³ Ω cm respectively, which is determined using the four probe method. Activation energy of these thin films was determined by Arrhenius plot.     

Characterization of molybdenum-doped indium oxide thin films by spray pyrolysis technique

In this research, indium oxide nanostructure undoped and doped with Mo were prepared on glass substrates using spray pyrolysis technique. Various parameters such as dopant concentration and deposition temperatures were studied. Structural properties of these films were investigated by X-ray diffraction and scanning electron microscopy. Electrical and optical properties have been studied by Hall effect and UV–Visible spectrophotometer, respectively. The thickness of the films was determined by PUMA software. The variation of refractive index, extension coefficient and bandgap of these films also were investigated.     

Transparent conducting lithium-doped nickel oxide thin films by spray pyrolysis technique

Nickel oxide (NiO) and lithium-doped nickel oxide films were deposited by the spray pyrolysis technique using NiCl2 and LiCl as starting materials. All the films were greenish-grey in colour and confirmed by X-ray analysis. The best NiO films were obtained when the substrate temperature, Ts=480 °C where a conductivity of 2.1×10-1Ω-1 cm-1 and transparency above 80% in the visible region are achieved. High transparency (above 80%) and highly conducting NiO films were obtained when doped with lithium. This revised version was published online in November 2006 with corrections to the Cover Date.     

Physical properties of CdS:Ga thin films synthesized by spray pyrolysis technique

This paper reports the investigation of physical properties of CdS:Ga thin films grown for the first time by a simple spray pyrolysis method as a function of Ga-doping level from 0 to 8 at.%. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive photoelectron spectroscopy, transmittance, photoluminescence, Hall effect and resistivity measurements are utilized to search for the structural, morphological, chemical, optical and electrical properties of as-prepared samples. XRD data confirm the presence of hexagonal structure with a strong (101) preferred orientation. SEM results show that the surface morphology varies significantly via Ga-doping, particularly 6 at.% doping level. Optical transparency is improved by the lower Ga-doping (2 and 4 at.%) whereas higher doping concentration (6 and 8 at.%) causes a poor transmission in the visible region. With respect to CdS (2.42 eV), the calculated band gap values at first enhances for 2 at.% Ga-doping and reaches to 2.43 eV. But, further increase in Ga-doping amount leads to a drop in the band gap value (2.39 eV) for 8 at.% Ga-doping. Electrical analyses display that 2 at.% Ga-doped CdS thin films exhibit a maximum carrier density and a minimum resistivity that are related to the substitutional incorporation of Ga³⁺ ions at Cd²⁺ ions. However, higher doping of Ga atoms into CdS gives rise to a gradual diminish in the carrier concentration and a rise in the resistivity. Based on all the data, it should be concluded that 2 at.% Ga-doped CdS thin films exhibit the best optical and electrical properties that can be used in the optoelectronic applications.     

Preparation and characterization of copper(II) oxide thin films grown by a novel spray pyrolysis method

A novel spray pyrolysis reactor was used to prepare thin films of CuO on silica substrates. The resulting films were characterized by x-ray diffraction, electron microscopy, optical and electrical measurements. The films were single phase, homogeneous, and uniform.     

Effect of indium doping on zinc oxide films prepared by chemical spray pyrolysis technique

We report the conducting and transparent In doped ZnO films fabricated by a homemade chemical spray pyrolysis system (CSPT). The effect of In concentration on the structural, morphological, electrical and optical properties have been studied. These films are found to show (0 0 2) preferential growth at low indium concentrations. An increase in In concentration causes a decrease in crystalline quality of films as confirmed by X-ray diffraction technique which leads to the introduction of defects in ZnO. Indium doping also significantly increased the electron concentrations, making the films heavily n type. However, the crystallinity and surface roughness of the films decreases with increase in indium doping content likely as a result of the formation of smaller grain size, which is clearly displayed in AFM images. Typical optical transmittance values in the order of (80%) were obtained for all films. The lowest resistivity value of 0.045 Ω-m was obtained for film with 5% indium doping.     

Synthesis and characterization of nanostructured nickel oxide thin films prepared with chemical spray pyrolysis

Nickel oxide thin films have been deposited in an open atmosphere onto glass substrates by chemical spray pyrolysis using aqueous nickel acetate solutions and air as driving gas. The films show a strong variation in the surface morphology depending on the substrate temperature and the precursor solution flux. At 350 °C substrate temperature, a reticular tissue-like film morphology is obtained, becoming the reticular nickel oxide fibres of the film thicker with increasing precursor solution flux. At 450 °C substrate temperature, the film growth rate is 4 times slower and a highly symmetric self-ordering of the material at nanometer length scale occurs. These films consist of interconnected grains separated by pores, both of about 100 nm in size. XRD and TEM revealed that the films are cubic NiO, being the crystallite size around 10 nm. The optical band gap of the films decreases strongly for increasing film thickness from 4.3 eV to 3.65 eV.     

Influence of substrate temperature on the structural,optical and electrical properties of ZnO thin films prepared by spray pyrolysis

The influence of substrate temperature on the structural, optical and electrical properties of ZnO films prepared by the spray pyrolysis method using aqueous solution of zinc acetate has been investigated. The films are polycrystalline and X-ray diffraction measurements show a strong preferred orientation along the [002] plane which is strongly dependent on the substrate temperature. Optical absorption spectra, show high transparency of the film (90–95% transmission) in the visible range, with a sharp absorption edge around 375 nm wavelength of light which closely corresponds to the intrinsic band gap of ZnO (3.3 eV). ZnO films with the lowest resistivity, which is due to the increased mobility resulting from the improvement of the crystallinity of the films, can be prepared at a substrate temperature of 490 °C.     

Influence of substrate temperature on ultraviolet emission of ZnO films prepared by ultrasonic spray pyrolysis

ZnO films were deposited on MgO substrates (ZnO/MgO) by ultrasonic spray pyrolysis. Substrate temperature varied from 200 to 350°C. The crystallographic properties and surface morphologies of the ZnO/MgO films were studied by X-ray diffraction and scanning electron microscopy. The properties of photoluminescence (PL) for the films were investigated by dependence of PL spectra on the substrate temperature and the ambient temperature. Ultraviolet (UV) emission peak (3.37 eV) was dominantly detected at 18 K, which sustained at 300 K with a reduced value of the peak energy. The ZnO/MgO films prepared at 350°C showed the strongest UV emission peak at 18 and 300 K among the films in this study.     

Fabrication of copper oxide thin films by the drop chemical deposition technique

Copper oxide thin films were deposited by the drop chemical deposition technique using an aqueous solution containing CuSO₄ and Na₂SO₃. The deposited films were cubic crystalline structure and had O/Cu ratio of ～0.77 with a very small amount of sulfur. The surface morphology of the films appeared compact without any crack. In the optical transmission measurement, a clear absorption edge was observed near 800 nm wavelength. Photo-electrochemical measurement confirmed the p-type conductivity and photosensitivity of the films. Cu_xO-based heterojunctions with ZnO were fabricated, and rectification properties and weak photovoltaic effects were observed.     

Influence of substrate temperature and solution molarity on CuO thin films' properties prepared by spray pyrolysis

Journal of Materials Science: Materials in Electronics - In the present work, we have investigated the influence of substrate temperature and solution concentration on copper oxide (CuO) thin film...     

Influence of the doping and annealing atmosphere on zinc oxide thin films deposited by spray pyrolysis

Undoped and doped (indium and aluminium) zinc oxide (ZnO) thin films have been prepared by spray pyrolysis, and the effect of the doping and annealing atmosphere on the electrical, optical and structural properties of the produced films has been investigated. The deposited films have a high resistivity. Annealing the films in an argon atmosphere or under vacuum leads to a substantial reduction of the electrical resistivity of the films and to an increase on the degree of cristallinity of the deposited material. The most pronounced changes were observed in the films annealed in Argon. The results also indicate that doping highly influences the electrical and structural properties of the films, which is more pronounced in the films doped with Indium.     

Characterization of FeS2-pyrite thin films synthesized by sulphuration of amorphous iron oxide films pre-deposited by spray pyrolysis

FeS₂-thin films with good crystallinity were synthesized by a simple method which consists of sulphuration, under vacuum, of amorphous iron oxide thin films pre-deposited by spray pyrolysis of FeCl₃·6H₂O (0.03 M)-based aqueous solution onto glass substrates heated at 350 °C. At optimum sulphuration temperature (450 °C) and duration (6 h), black green layers having granular structure and high absorption coefficient (5.10⁴ cm⁻¹) were obtained. The study of the electrical properties of the as-prepared films vs. the temperature variations showed three temperature domain dependence of the conductivity behaviour. The first one corresponds to the high temperature range (330 K–550 K) for which an Arrhenius plot type was obtained. The activation energy value was estimated at about 61.47 meV. The second domain corresponding to the intermediate temperature range (80 K–330 K) showed a variable activation energy between the grain boundaries. The barrier height, q¯, was estimated to 27±0.5 meV, and the standard deviation, qσ, was evaluated at about 14±0.5 meV. We found that at lower temperatures (20 K–80 K), the conductivity is governed by two conduction types. The density of localised states, was about 2.45×10²⁰ eV⁻¹ cm⁻³.     

Substrate influences on the properties of SnS thin films deposited by chemical spray pyrolysis technique for photovoltaic applications

Herein, we report on tin monosulfide (SnS) thin films elaborated by the Chemical Spray Pyrolysis (CSP) technique onto various substrates as simple glass, ITO-, and Mo-coated glasses in order to study the influence of substrates on the physical and chemical properties of Sns thin films. Structural analysis revealed that all films crystallize in orthorhombic structure with (111) as the sole preferential direction without secondary phases. In addition, film prepared onto pure glass exhibits a better crystallization compared to films deposited onto coated glass substrates. Raman spectroscopy analysis confirms the results obtained by X-ray diffraction with modes corresponding well to SnS single-crystal orthorhombic ones (47, 65, 94, 160, 186, and 219 cm ^?1) without any additional parasite secondary phase like Sn₂S₃ or SnS₂. Field emission scanning electron microscope revealed that all films have a cornflake-like particles surface morphology, and energy dispersive X-ray spectroscopy analysis showed the presence of sulfur and tin with a nearly stoichiometric ratio in films deposited onto pure glass. High surface roughness and large grains are observable in film deposited onto glass. From optical spectroscopy, it is inferred that band gap energy of SnS/glass and SnS/ITO were 1.64 and 1.82 eV, respectively.     

Substrate temperature effects on the tin oxide films prepared by spray pyrolysis

Indium-doped tin oxide films were prepared by the spray pyrolysis technique at different substrate temperatures ranging from 400–525 C. Texture coefficients for (200) and (112) reflections of tetragonal SnO₂ were calculated. The surface morphology of the prepared films was revealed by using scanning electron microscopy. A dendrite structure was observed in the films deposited at a substrate temperature of 525 C. The obtained specific resistances were correlated with those obtained from X-ray diffraction analysis and scanning electron microscopy. A study of the effect of film thickness on the plane of preferred orientation was carried out.     

Growth and characterization of indium oxide thin films prepared by spray pyrolysis

Highly transparent and conducting indium oxide thin films are prepared on glass substrates from precursor solution of indium chloride. These films are characterized by X-ray diffraction, scanning electron microscopy and optical transmission. The preferential orientation of these films is found to be sensitive to deposition parameters. A comparative study has been made on the dependence on the thickness of the film on substrate temperatures with aqueous solution and 1:1 C₂H₅OH and H₂O as precursors. Films deposited at optimum conditions have 167 nm thickness and exhibited a resistivity of 2.94 × 10⁻⁴ Ω m along with transmittance better than 82% at 550 nm. The analytical expressions enabling the derivation of the optical constants of these films from their transmission spectrum only have successfully been applied. Finally, the refractive index dispersion is discussed in terms of the single-oscillator Wemple and Didomenico model.     

Growth and characterization of indium oxide thin films prepared by spray pyrolysis

Highly transparent and conducting indium oxide thin films are prepared on glass substrates from precursor solution of indium chloride. These films are characterized by X-ray diffraction, scanning electron microscopy and optical transmission. The preferential orientation of these films is found to be sensitive to deposition parameters. A comparative study has been made on the dependence on the thickness of the film on substrate temperatures with aqueous solution and 1:1 C₂H₅OH and H₂O as precursors. Films deposited at optimum conditions have 167 nm thickness and exhibited a resistivity of 2.94 × 10⁻⁴ Ω m along with transmittance better than 82% at 550 nm. The analytical expressions enabling the derivation of the optical constants of these films from their transmission spectrum only have successfully been applied. Finally, the refractive index dispersion is discussed in terms of the single-oscillator Wemple and Didomenico model.