Influence of Mn doping on structural,optical and electrical properties of CdO thin films prepared by cost effective spray pyrolysis method

Transparent and conducting cadmium oxide (CdO) and manganese doped CdO (Mn: CdO) thin films were deposited using a low cost spray pyrolysis method on the glass substrate at 300 °C. For Mn doping, various concentrations of manganese acetate (1–3 wt%) was used in the spraying precursor solution. The structural, electrical and optical properties of CdO and Mn: CdO films were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), UV–vis and Hall measurement. X-ray diffraction study reveals that the CdO and Mn: CdO films are possessing cubic crystal structures. SEM and AFM studies reveal that the grain size and roughness of the films are increased with increasing Mn doping concentration. Optical transmittance spectra of the CdO film decreases with increasing doping concentration of manganese. The optical band gap of the films decreases from 2.42 eV to 2.08 eV with increasing concentration of manganese. A minimum resistivity of 1.11×10⁻³ Ω cm and maximum mobility of 20.77 cm² V⁻¹ s⁻¹ is achieved for 1 wt% of manganese doping.     

Effect of fluorine doping on the structural,optical and electrical properties of spray deposited cadmium stannate thin films

Cadmium stannate (Cd₂SnO₄) thin films were coated on Corning 1737 glass substrates at 540 °C by spray pyrolysis technique, from the aqueous solution of cadmium acetate and tin (II) chloride precursors. Fluorine doped Cd₂SnO₄ (F: Cd₂SnO₄) thin films were prepared by adding ammonium fluoride in the range of 0–5 wt% of the total weight of cadmium acetate and tin (II) chloride in the spray solution. Thickness of the prepared films is about 300 nm. X-ray diffraction analysis of the Cd₂SnO₄ and 3 wt% F: Cd₂SnO₄ films shows the signature for the growth along (222) direction. Scanning electron micrographs showed that fluorine doping effectively modifies the surface morphology of Cd₂SnO₄ films. Average optical transmittance in the visible region (500–850 nm) for Cd₂SnO₄ is ~79% and it is increased to ~83% for 1 wt% doping concentration of the NH₄F in the solution. Fluorescence spectra of F: Cd₂SnO₄ (1 wt% and 3 wt%) exhibit peak at 601 nm. F: Cd₂SnO₄ film (1 wt%) shows mobility of ~42 cm²/V s, carrier concentration of ~9.5×10¹⁹ cm^?3 and resistivity of ~1.5×10^?3 Ω cm.     

Effect of annealing temperature on structural,electrical and optical properties of spray pyrolytic nanocrystalline CdO thin films

Nanocrystalline CdO thin films were prepared onto a glass substrate at substrate temperature of 300 °C by a spray pyrolysis technique. Grown films were annealed at 250, 350, 450 and 550 °C for 2.5 h and studied by the X-ray diffraction, Hall voltage measurement, UV-spectroscopy, and scanning electron microscope. The X-ray diffraction study confirms the cubic structure of as-deposited and annealed films. The grain size increases whereas the dislocation density decreases with increasing annealing temperature. The Hall measurement confirms that CdO is an n-type semiconductor. The carrier density and mobility increase with increasing annealing temperature up to 450 °C. The temperature dependent dc resistivity of as-deposited film shows metallic behavior from room temperature to 370 K after which it is semiconducting in nature. The metallic behavior completely washed out by annealing the samples at different temperatures. Optical transmittance and band gap energy of the films are found to decrease with increasing annealing temperature and the highest transmittance is found in near infrared region. The refractive index and optical conductivity of the CdO thin films enhanced by annealing. Scanning electron microscopy confirms formation of nano-structured CdO thin films with clear grain boundary.     

Influences of post-annealing temperature on the structural and electrical properties of mixed oxides (CuFeO2 and CuFe2O4) thin films prepared by spray pyrolysis technique

P-type mixed oxides (CuFeO₂ and CuFe₂O₄) transparent conducting thin films have been successfully deposited on p-type Si (111) substrates at 450 °C by spray pyrolysis deposition (SPD) and annealed at 800 °C for 2 h. The crystal structure, surface morphology and electrical property have been investigated. It is observed that the CuFeO₂ and CuFe₂O₄ thin films as deposited and annealed, have polycrystalline hexagonal structure and the crystallite size increases by annealing processes. The electrical property of the Ni/CuFeO₂/Si Metal–Semiconductor–Metal (MSM) photo detectors was investigated using the current–voltage (I–V) measurements. The barrier heights ϕ_Β of Ni/CuFeO₂/Ni MSM thin films of as deposited and annealed on Si substrates were calculated and its values are 0.478, 0.345 eV, respectively with an applied bias voltage of 3 V.     

Structural and optical characterization of V- and W-doped SnS2 thin films prepared by spray pyrolysis

Tin(IV) sulfide (SnS₂) doped with V ions are promising intermediate band solar cell materials. In this work, we demonstrate the possibility of preparing thin films of Sn_0.75V_0.25S₂ and Sn_0.75W_0.25S₂ using the spray pyrolysis deposition method. Successful attempts are reported when a water/ethanol mixture at 9:1 ratio was used as a solvent and the deposition temperature was set at 360 °C. The samples were characterized by x-ray diffraction, atomic force microscopy, micro-Raman spectroscopy and UV–Vis–NIR optical transmission measurements. The analysis of the data showed that all the samples are crystalline with no impurities. Optical transmission data revealed that the direct and the indirect band gaps of SnS₂ are found to be 2.25 and 2.15 eV, respectively. These values decrease as the samples were doped with V- and W-ions. The direct band gap values are found to fall within the 1.56–1.75 eV range while the indirect band gap values are found to be within the 1.55–1.70 eV range. Furthermore, the effect of doping caused the optical absorption coefficient to approximately be double of its values in a broad range extending from the visible to the near infrared regions. These findings suggest that Sn_0.75V_0.25S₂ and Sn_0.75W_0.25S₂ can be used as new potential solar energy absorbers in photovoltaic devices.     

Growth and molarity effects on properties of alumina thin films obtained by spray pyrolysis

Various and versatile applications of alumina in materials science and engineering specially in semiconductor and energy conversion technology encouraged us to prepare and investigate its physical properties as much as possible. Hence, after depositing of alumina thin films on glass substrates by a spray pyrolysis technique, structural, morphological, and optical properties of the films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and UV–visible spectrophotometry. Different optical quantities, such as optical band gap, refractive index and extinction coefficient, were determined in this article for different molarities (from 0.10 M to 0.25 M) at two specific substrate temperatures (250 °C and 500 °C). XRD results showed the prevailing amorphous phase in all samples as expected, whereas SEM, XPS, and FTIR presented the presence of molarity effects on alumina properties. Decrease of optical transmittance with molarity increase was notable. Using the transmittance data other optical quantities were obtained by a numerical approximation method.     

Impact of substrate temperature on the structural,optical and electrical properties of thermally evaporated SnS thin films

Tin Sulfide thin films were deposited on soda lime glass substrates at three different substrate temperatures using thermal evaporation technique. The impact of substrate temperature on the deposited films has been studied thoroughly. Surface morphology was modified with the substrate temperature. XRD spectra shows orthorhombic end-centered type SnS having (1 1 0) orientation. The crystallite size increases with the increase in the substrate temperature. At a high substrate temperature (450 °C) small grains form on the surface and crystallinity decreases. The effect of substrate temperature on optical and electrical properties has been studied using UV–Vis–NIR Spectrophotometer and Hall effect respectively. With the increase in the substrate temperature there is a substantial decrease in the transmittance and bandgap value. Refractive index (n), dielectric constant (ε₁) and extinction co-efficient (k) have also been calculated for different substrate temperatures.     

Effect of Fe-doping on the structural and optical properties of ZnO thin films prepared by spray pyrolysis

Fe-doped ZnO thin films have been prepared by spray pyrolysis on glass substrates and the influence of Fe-doping concentration on the structural and optical properties of the films has been studied.The X-ray diffraction (XRD) analysis shows that Fe doping has a significant effect on crystalline quality,grain size and strain in the thin films.The best crystalline structure is obtained for 3 at%Fe doping as observed from scanning electron microscopy (SEM) and XRD.However,lower or higher Fe-doping degrades the crystalline quality in turn.Moreover,UV spectroscopy demonstrates the influence of Fe-incorporation on visible range transmittance of ZnO where the best transmittance is obtained for 3 at%doping.The results have been illustrated simultaneously focusing previous results obtained from literature.     

Effect of substrate temperature on indium tin oxide (ITO) thin films deposited by jet nebulizer spray pyrolysis and solar cell application

This study focused on the effect of substrate temperature (350 °C, 400 °C, and 450 °C) on morphological, optical, and electrical properties of indium tin oxide (ITO) films deposited onto porous silicon/sodalime glass substrates through jet nebulizer spray pyrolysis for use in heterojunction solar cells. X-ray diffraction analysis confirmed the formation of pure and single-phase In₂O₃ for all the deposited films whose crystallinity was enhanced with increasing substrate temperature, as shown by the increasing (222) peak intensity. Morphological observations were conducted using scanning electron microscopy to reveal the formation of continuous dense films composed of nanograins. The UV–vis spectra revealed that the transmittance increased with increasing substrate temperature, reaching a value of over 80% at 450 °C. The photoelectric performance of the solar cell was studied using the I–V curve by illuminating the cell at 100 mW/cm². A high efficiency (η) of 3.325% with I_sc and V_oc values of 14.8 mA/cm² and 0.60 V, respectively, was attained by the ITO solar cell annealed at 450 °C.     

Effect of precursor solutions on the structural and optical properties of sprayed NiO thin films

Nickel oxide thin films were deposited by a simple and low-cost spray pyrolysis technique using three different precursors: nickel nitrate, nickel chloride, and nickel acetate on corning glass substrates. X-ray diffraction show that the NiO films are polycrystalline and have a cubic crystal structure, although predominantly with a preferred 111-orientation in the growth direction and a random in-plane orientation. The deconvolution of the Ni 2p and O 1s core level X-ray photoelectron-spectra of nickel oxides produced by using different precursors indicates a shift of the binding energies. The sprayed NiO deposited from nickel nitrate has an optical transmittance in the range of 60–65% in the visible region. The optical band gap energies of the sprayed NiO films deposited from nickel nitrate, nickel chloride and nickel acetate are 3.5, 3.2 and 3.43 eV respectively. Also, the extinction coefficient and refractive index of NiO films have been calculated from transmittance and reflectance measurements. The average value of refractive index for sprayed films by nickel nitrate, nickel chloride and nickel acetate are 2.1, 1.6 and 1.85 respectively. It is revealed that the band gap and refractive index of NiO films by using nickel nitrate corresponds to the commonly reported values. We attribute the observed behavior in the optical band gap and optical constants as due to the change of the Ni/O ratio.     

Effect of Pb:S molar ratio in precursor solution on the properties of lead sulphide thin films by ultrasonic spray pyrolysis

In this work, PbS thin films were deposited onto glass substrate at 225 °C by spraying precursor solution prepared with different molar ratio of lead acetate and thiourea as a source of Pb²⁺ and S^2- respectively in order to investigate the effect of Pb:S molar ratio in the precursor solution on the physical properties of PbS thin films. Structural investigations carried out by X-ray diffractometer have shown that all films have fcc cubic structure and the average crystal size increased from 11 nm to 25 nm with the increasing the thiourea ratio in the precursor solution. In order to analyze the surface morphology of PbS thin films, AFM and SEM images were taken and elemental analysis of the films was performed by EDS. Optical transmittance and absorption spectra show that all deposited films have fairly low transmittance and high absorbance in the visible region. Additionally, it was determined that optical band gap of the deposited films were varied between 1.18 eV and 1.37 eV. As a consequence of electrical investigations, it was seen that all films have p-type conductivity and electrical resistivity decreased by increasing thiourea molar ratio in the precursor solution. All examinations have revealed that the molar ratio of lead acetate and thiourea has a significant effect on the physical properties of PbS thin films.     

Influence of heat treatment on the structural,optical and electrical properties of Cd20Sn10Se70 thin films

The effect of annealing temperature (T_a) on the structural, optical, and electrical properties of thermally evaporated Cd₂₀Sn₁₀Se₇₀ thin films has been investigated. Differential Thermal Analysis (DTA) was used to determine the glass transition temperature (T_g) of the prepared alloy. X-ray diffraction studies showed that the as-deposited film and the films that were annealed at T_a<T_g are of low crystallinity. On annealing above T_g, these films showed a polycrystalline nature. The surface morphology and microstructure of as-deposited and annealed films have been examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Their optical constants were calculated from the transmittance measurements in the range 200–2500 nm. The dispersion of refractive index was analyzed in terms of the single-oscillator Wemple-Di Domenico model. Analysis of the optical absorption data indicates that the optical band gap E_g of these films obeys Tauc׳s relation for the allowed direct transition. The optical band gap E_g as well as the activation energy for the electrical conduction ∆E were found to increase with increase of annealing temperature up to T_g, whereas above T_g there is a remarkable decrease in both E_g and ∆E. The obtained results were interpreted in terms of the Mott-Davis model and amorphous–crystalline transformation.     

Effects of molarity on structural,optical, morphological and CO2 gas sensing properties of nanostructured copper oxide films deposited by spray pyrolysis

In this paper, we have exposed the effects of molarity on structural, optical, morphological and gas sensing properties of copper oxide films deposited by pneumatic spray pyrolysis method. The molar concentration was varied from 0.05 to 0.3 M. X-ray diffractograms showed the formation of a single phase CuO for films prepared with 0.05 and 0.1 M concentrations. A secondary phase Cu₂O was obtained for 0.2 and 0.3 M concentrations. Optical measurements showed that 0.05 M concentration provides a film with the best transparency in the visible and near infrared regions. The thickness values were between 2 and 110 µm. Moreover, the contact angle measurements have shown that all the deposited films are hydrophobic with angles between 103° and 121°. The morphological properties were investigated using SEM and AFM. According to SEM and AFM micrographs, 0.05 M is the concentration that leads to porous structure. The gas sensing measurements confirm that this porous surface structure is the most sensitive to different CO₂ concentrations.     

Enhancement of photoluminescence in Sr doped ZnO thin films prepared by spray pyrolysis

Photoluminescence characteristics of strontium doped zinc oxide (ZnO:Sr) thin films grown by spray pyrolysis method were investigated. The ZnO:Sr films were highly transparent having polycrystalline hexagonal wurtzite structure. A redshift of 130 meV in the optical band gap was observed owing to atomic size mismatch induced defect states and increase in the crystallite size in ZnO:Sr films. The enhancement of intensity of violet emission in room temperature photoluminescence by 250% is in correlation with the improved surface morphology at higher concentration of Sr in ZnO:Sr thin film. The observed increment in visible emissions is attributed to Sr induced oxygen vacancy related recombination in ZnO.     

Effects of substrate temperature on the properties of CdSnSe thin films deposited by nebulizer spray pyrolysis technique

Thin films of cadmium tin selenide (CdSnSe) have been prepared on glass substrates at different temperatures by the nebulizer spray pyrolysis (NSP) technique using aqueous solutions of cadmium chloride (CdCl₂), tin chloride (SnCl₂) and sodium selenosulphate (Na₂SeSO₃). The deposited films were characterized by structural, morphological, compositional, optical and electrical properties. X-ray diffraction studies confirm that the CdSnSe films are polycrystalline in nature having mixed phase (hexagonal+cubic) crystal structure with preferential orientation (102) plane which corresponds to hexagonal crystal structure. Scanning electron microscopy studies reveal that the prepared films are having smooth and uniform surface with dense surface morphology well-covered over the entire substrate surface without any cracks. The UV–vis spectroscopy confirms the formation of good transparent CdSnSe films with an average transmission ∼60% in the visible region. Optical band gap energies of the films are found to be varied from 1.6–1.625 eV depending on the substrate temperatures. The temperature dependence of the electrical conductivity during the heat treatment was also studied. The electrical conductivity of the films is found to be in the order of 10⁻³ Ω-cm⁻¹ and increases with temperature.     

Effect of doping concentration on the properties of bismuth doped tin sulfide thin films prepared by spray pyrolysis

Bismuth doped tin sulfide (SnS:Bi) thin films were deposited onto glass substrates by the spray pyrolysis technique at the substrate temperature of 350 °C. The effect of doping concentration [Bi/Sn] on their structural, optical and electrical properties was investigated as a function of bismuth doping between 0 and 8 at%. The XRD results showed that the films were polycrystalline SnS with orthorhombic structure and the crystallites in the films were oriented along (111) direction. Atomic force microscopy revealed that the particle size and surface roughness of the films increased due to Bi-doping. Optical analysis exhibited the band gap value of 1.40 eV for SnS:Bi (6 at%) which was lower than the band gap value for 0 at% of Bi (1.60 eV). The film has low resistivity of 4.788×10⁻¹ Ω-cm and higher carrier concentration of 3.625×10¹⁸ cm⁻³ was obtained at a doping ratio of 6 at%.     

Structural, optical and electrical properties of zinc oxide thin films deposited by a spray pyrolysis technique

Zinc oxide (ZnO) thin films were deposited on glass substrates by spray pyrolysis technique decomposition of zinc acetate dihydrate in an ethanol solution with 30 mL of deposition rate, the ZnO thin films were deposited at two different temperatures: 300 and 350 ℃. The substrates were heated using the solar cells method. The substrate was R217102 glass, whose size was 30 × 17.5 × 1 mm³. The films exhibit a hexagonal wurtzite structure with a strong (002) preferred orientation. The higher value of crystallite size is attained for sprayed films at 350 ℃, which is probably due to an improvement of the crystallinity of the films at this point. The average trans mittance of obtain films is about 90%-95%, as measured by a UV-vis analyzer. The band gap energy varies from 3.265 to 3.294 eV for the deposited ZnO thin film at 300 and 350 ℃, respectively. The electrical resistivity measured of our films are in the order 0.36 Ω·cm.     

Study of structural,electrical and photoconductive properties of F and P co-doped SnO2 transparent semiconducting thin film deposited by spray pyrolysis

Transparent conducting phosphorus–fluorine co-doped tin oxide (SnO₂:(P, F)) thin films have been deposited onto preheated glass substrates using the spray pyrolysis technique by the various dopant quantity of spray solution. The [F/Sn] atomic concentration ratio (x) in the spray solution is kept at value of 0.7 and the [P/Sn] atomic ratio (y) varied at values of 0, 0.001, 0.005, 0.01, 0.02, 0.04, 0.06, and 0.10. The structural, morphological, X-ray diffraction, electrical, optical and photoconductive properties of these films have been studied. It is found that the films are polycrystalline in nature with a tetragonal crystal structure corresponding to SnO₂ phase having orientation along the (110) plane and polyhedrons like grains appear in the FE-SEM image. The average grain size increases with increasing P-dopant concentration. The compositional analysis of FTO:P thin films were studied using EDAX. The Hall effect measurements have shown n-type conductivity in all deposited films. The lowest sheet resistance and highest the carrier concentration about 6.4 Ω/□ and 7.4×10²², respectively, were obtained for the film deposited with y=[P/Sn]=0.01. The films deposited with y=0.04 phosphorus-doped SnO₂:F shows 68% optical transparency. From the photoconductive studies, the P-doped films exhibited sensitivity to incident light especially in y=0.04. The electrical resistivity and carrier concentration vary in rang 6.2×10⁻⁴ to 21.1×10⁻⁴ Ω cm and 7.4×10²² to 1.3×10²² cm⁻³, respectively.     

Effects of substrate temperature on electrical and structural properties of copper thin films

This paper addresses the effects of substrate temperature on electrical and structural properties of dc magnetron sputter-deposited copper (Cu) thin films on p-type silicon. Copper films of 80 and 500 nm were deposited from Cu target in argon ambient gas pressure of 3.6 mTorr at different substrate temperatures ranging from room temperature to 250 °C. The electrical and structural properties of the Cu films were investigated by four-point probe and atomic force microscopy. Results from our experiment show that the increase in substrate temperature generally promotes the grain growth of the Cu films of both thicknesses. The RMS roughness as well as the lateral feature size increase with the substrate temperature, which is associated with the increase in the grain size. On the other hand, the resistivity for 80 nm Cu film decreases to less than 5 μΩ-cm at the substrate temperature of 100 °C, and further increase in the substrate temperature has not significantly decreased the film resistivity. For the 500 nm Cu films, the increase in the grain size with the substrate temperature does not conform to the film resistivity for these Cu films, which show no significant change over the substrate temperature range. Possible mechanisms of substrate-temperature-dependent microstructure formation of these Cu films are discussed in this paper, which explain the interrelationship of grain growth and film resistivity with elevated substrate temperature.     

Effect of co-doping concentration on structural,morphological, optical and electrical properties of aluminium and indium co-doped ZnO thin films deposited by ultrasonic spray pyrolysis

In this work, we reported a chemical approach to prepare aluminium and indium co-doped ZnO thin films (AIZO) by ultrasonic spray pyrolysis. Film depositions were carried out on soda lime glass substrates at 425 °C by using a spray solution containing zinc acetate as zinc precursor, aluminium acetylacetonate as Al dopant source and indium (III) acetate as In dopant source. Physical properties such as structural, morphological, optical and electrical properties were studied with respect to the equal variations in co-dopants concentration (0.5–3 at%). X-ray diffraction patterns proved that films are poly crystalline with (002) preferential orientation. Scanning electron microscopy analysis showed that AIZO films grown like hexagonal nanopyramids, elongated grains and irregular trigonals. Optical transmittance ~85% and a minimum resistivity of 1.3×10⁻³ Ω cm, are achieved for films when co-doped with 1.5 at% of Al and 1.5 at% of In, confirm that AIZO films are suitable for transparent conductive oxide (TCO) applications.