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.     

Effects of Sb,Zn doping on structural,electrical and optical properties of SnO2 thin films

Highly transparent, low resistive pure and Sb, Zn doped nanostructured SnO₂ thin films have been successfully prepared on glass substrates at 400° C by spray pyrolysis method. Structural, electrical and optical properties of pure and Sb, Zn doped SnO₂ thin films are studied in detail. Powder X-ray diffraction confirms the phase purity, increase in crystallinity, size of the grains (90–45 nm), polycrystalline nature and tetragonal rutile structure of thin films. The scanning electron microscopy reveals the continuous change in surface morphology of thin films and size of the grains decrease due to Sb, Zn doping in to SnO₂. The optical transmission spectra of SnO₂ films as a function of wavelength confirm that the optical transmission increases with Sb, Zn doping remarkably. The optical band gap of undoped film is found to be 4.27 eV and decreases with Sb, Zn doping to 4.19 eV, 4.07 eV respectively. The results of electrical measurements indicate that the sheet resistance of the deposited films improves with Sb, Zn doping. The Hall measurements confirm that the films are degenerate n-type semiconductors.     

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%.     

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.     

Study of some physical properties of ultrasonically spray deposited silver doped lead sulphide thin films

In this study, undoped and Ag doped PbS thin films at different concentrations were deposited onto glass substrates at 225 °C by using ultrasonic spray pyrolysis technique, in order to investigate the effect of Ag doping on the physical properties of PbS thin films. Structural investigations revealed that all doped PbS:Ag thin films have cubic structure and Ag doping enhances crystalline level of PbS thin films. It was determined that average crystallite size of PbS:Ag thin films increased from 24 nm to 49 nm by increasing Ag doping concentration. Morphological studies showed that surfaces of the films become denser after Ag doping. Optical transmittance and absorption spectra revealed that all deposited thin films have low transmission and high absorbance within the visible region and band gap energy of the PbS:Ag thin films were determined to be in the range of 1.37 eV and 1.28 eV by means of optical method. Electrical conductivity type of PbS:Ag films was determined to be p-type and calculated electrical resistivity was found to be lowest for Ag-doped PbS thin films at 2%.     

Structural,morphological, electrical and optical studies of Cr doped SnO2 thin films deposited by the spray pyrolysis technique

Tin oxide (SnO₂) and chromium (Cr) doped tin oxide (Cr:SnO₂) thin films were deposited on the preheated glass substrates at 673 K by spray pyrolysis. Concentration of Cr was varied in the solution by adding chromium (III) chloride hexahydrate from 0 to 3 at%. The effect of Cr doping on the structural, electrical and optical properties of tin oxide films is reported. X-ray diffraction pattern confirms the tetragonal crystal structure for undoped and Cr doped tin oxide films. Scanning electron microscopic photographs show the modification of surface morphology of tin oxide film due to varying concentration of Cr. X-ray photoelectron spectra of Cr:SnO₂ (3 at%) thin film revealed the presence of carbon, tin, oxygen, and chromium. Carrier concentration and mobility of the SnO₂ films decrease with increasing concentration of Cr and 0.5 at% Cr doped tin oxide film acquires a mobility of 70 cm²/V s. Average optical transmittance in the 550–850 nm range varies from 38% to 47% with varying Cr concentration in the solution.     

Influence of Sn content on properties of ZnO:SnO2 thin films deposited by ultrasonic spray pyrolysis

The present work is devoted to the preparation of zinc oxide (ZnO): tin oxide (SnO₂) thin films by ultrasonic spray technique. A set of films are deposited using a solution formed with zinc acetate and tin chloride salts mixture with varied weight ratio R=[Sn/(Zn+Sn)]. The ratio R is varied from 0 to 100% in order to investigate the influence of Sn concentration on the physical properties of ZnO:SnO₂ films. The X rays diffraction (XRD) analysis indicated that films are composed of ZnO and SnO₂ distinct phases without any alloys or spinnel phase formations. The average grain size of crystallites varies with the ratio R from 17 to 20 nm for SnO₂ and from 24 to 40 nm for ZnO. The obtained films are highly transparent with a transmission coefficient equal to 80%. An increase in Sn concentration increases both the effective band gap energy from 3.2 to 4.01 eV and the photoluminescence intensity peak assigned defects to SnO₂. The films electrical characterization indicated that films are resistive. Their resistivities vary between 1.2×10² and 3.3×10⁴ (Ω cm). The higher resistivity is measured in film deposited with a ratio R equal to 50%.     

Tuning optical,electrical and magnetic properties of fiber structured ZnO film by deposition temperature and precursor concentration

Highly transparent ZnO films were deposited on glass substrates using zinc acetate solution through cost effective spray pyrolysis method. A comprehensive study was carried out to understand the effects of deposition temperature and precursor concentrations on structure, surface morphology, optical, electrical and magnetic properties of the deposited films. All deposited films were polycrystalline in nature with hexagonal wurtzite structure. The films were preferentially oriented along (1 0 1) plane up to 723 K beyond which orientation changed to (0 0 2) plane. Irrespective of precursor concentration used, the films deposited at 673 K and 723 K showed fibrous structure. The films deposited at higher temperature led to enhanced transmittance and optical energy band gap. With higher precursor concentrations the transmittance decreased while the band gap increased. Photoluminescence studies revealed the presence of various defects leading to emission in the visible region apart from band to band transition near UV region. Lowest electrical resistivity was obtained for films deposited at 723 K which is of the order 10² Ω cm. At room temperature, all deposited films were diamagnetic while they were paramagnetic at 5 K.     

Study of structural and optical properties of nanostructured V2O5 thin films doped with fluorine

In this study, vanadium oxide (V₂O₅) was doped with different percentages of fluorine (F) and deposited on glass substrates by using spray pyrolysis method. The substrate temperature during the film deposition was kept constant at 450 °C. The obtained nanostructured thin films were characterised by X-ray Diffraction (XRD), UV–visible spectroscopy, and Scanning Electron Microscopy (SEM). The XRD results showed that F doped films are polycrystalline with main phase of β-V₂O₅ and with preferred orientation along (200). Increasing dopant to 30% improved crystallinity, but for more doping, the structure of samples tended to be amorphous. VF₂ phase was also observed when doping of F was increased to more than 10%. The incorporation of fluorine in nano-layers led to a decrease in optical absorption by 1.3 a.u. and an increase in band gap of energy from 2.23 to 2.83 eV. SEM images showed that the shape of grains was spherical with 10% doping and changed to bacilliform with 70% F concentration. The cyclic voltammetry results obtained for different samples showed expanded anodic and cathodic peaks for the undoped sample. The samples prepared with 20% and 40% F-doping level had milder anodic and cathodic peaks. However, by increasing the dopant to 70%, the peaks were expanded. The thin film with 40% F-doping showed the least resistance, but the resistance increased dramatically with 70% F dopant concentrations.     

Development of transparent conducting copper and iron co-doped cadmium oxide films: Effect of annealing in hydrogen atmosphere

Hydrogenated (annealed in hydrogen atmosphere) cadmium oxide (CdO) thin films co-doped with iron (Fe) of different levels and fixed (2.5%) copper (Cu) amount were deposited on glass and silicon wafer substrates by thermal evaporation. The films were characterised with X-ray fluorescence, X-ray diffraction, optical spectroscopy, and dc-electrical measurements. The obtained results show important improvements in the conductivity, mobility, and carrier concentration compared to un-doped and non-hydrogenated CdO. Hydrogenated CdO doped with 2.5% Cu and 1.3% Fe improved the conductivity (2293.6 S/cm) by ~46 times, mobility (78.31 cm²/V s) by ~11 times, and carrier concentration (1.82×10²⁰ cm⁻³) by ~4 times. This suggests the possibility of using CdO:Cu:Fe–H as transparent-conducting-oxide and dilute-magnetic-semiconductor field of applications.     

Influence of In doping on the structural,optical and acetone sensing properties of ZnO nanoparticulate thin films

Indium-doped zinc oxide (ZnO) nanoparticle thin films were deposited on cleaned glass substrates by spray pyrolysis technique using zinc acetate dihydrate [Zn(CH₃COO)₂ 2H₂O] as a host precursor and indium chloride (InCl₃) as a dopant precursor. X-ray diffraction results show that all films are polycrystalline zinc oxide having hexagonal wurtzite structure. Upon In doping, the films exhibit reduced crystallinity as compared with the undoped film. The optical studies reveal that the samples have an optical band gap in the range 3.23–3.27 eV. Unlike the undoped film, the In-doped films have been found to have the normal dispersion for the wavelength range 450–550 nm. Among all the films investigated, the 1 at% In-doped film shows the maximum response 96.8% to 100 ppm of acetone in air at the operating temperature of 300 °C. Even at a lower concentration of 25 ppm, the response to acetone in this film has been found to be more than 90% at 300 °C, which is attributed to the smaller crystallite size of the film, leading to sufficient adsorption of the atmospheric oxygen on the film surface at the operating temperature of 300 °C. Furthermore, In-doped films show the faster response and recovery at higher operating temperatures. A possible reaction mechanism of acetone sensing has been explained.     

Improving carrier mobility with vanadium doping of transparent conducting CdO

Cadmium oxide (CdO) is a transparent conducting oxide (TCO) with versatile applications, many of which are linked to its transparency in the Vis/NIR spectral range in addition to its unique electrical conductivity. Its optoelectronic properties can be controlled in order to bring them into a desired choice by doping method. Usually resistivity of TCO could be reduced by increasing N_el, which, in turns, reduces the transparency (especially in the NIR region) of TCO. Therefore, it is important to seek ways to reduce ρ by increasing of μ_el (rather than N_el) that also reduces the absorption.In the present work, CdO thin films doped with different amounts of vanadium (V) ions were deposited on glass and silicon wafer substrates by physical vapour deposition method. The films were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), optical absorption spectroscopy, and dc-electrical measurements. The obtained results show significant improvements in the conductivity (σ), mobility (μ), and carrier concentration (N_el) of host CdO. The measured utmost enhancement in conductivity by 420%, mobility by 766%, and carrier concentration by 201% for CdO films doped with 4–5 wt% V. This suggests the possibility of using V-doped CdO films in different TCO applications.     

The effect of Pb doping on the characteristic properties of spin coated ZnO thin films: Wrinkle structures

Un-doped and lead (Pb) doped ZnO thin films were deposited by sol–gel spin coating technique. Structural, morphological and optical properties of the films were investigated by means of Pb doping, in the range of 1–4% (with 1 at% step). X-ray diffraction results indicated that all films have hexagonal wurtzite crystal structure. (002) Reflection peak has been seen as the most intense peak and the highest texture coefficient value. Grain size values of the films varied from 19.68 nm to 13.37 nm with the increasing Pb incorporation. The top-view and cross sectional scanning electron microscope images demonstrated that the films were made up of wrinkle network structures and the films' thicknesses changed in the range of 400–276 nm. The direct optical band gap was calculated in 3 different functions and a significant harmony was observed among them. Additionally, all results indicated that the direct optical band gap and the Urbach values of the films increase with the increasing Pb doping content. Besides, the effects of Pb content on the photoluminescence properties of ZnO films were evaluated and it was observed that the decrease in the photoluminescence intensity was based on the Pb content. Moreover, the correlation between the optical and structural properties suggested that the optical band gap of Pb doped ZnO films were influenced by the lattice parameters a and c.     

Structural,optical, and photocatalytic properties of the spray deposited nanoporous CdS thin films; influence of copper doping,annealing, and deposition parameters

Nanoporous thin films of Cd_1−xCu_xS (0≤x≤0.06) were grown on a heated glass substrate employing a home-made spray pyrolysis technique. The influences of [Cu]/[Cd] and the annealing in the range 300–500 °C on the structural and morphological properties of the films were investigated by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), field emission scanning electron microscope (FE-SEM) and atomic force microscopy (AFM). The influences of Cu doping ratio, solution flow rate, and the deposition time on the optical properties and photocatalytic activity of these films are also reported. The films are of polycrystalline nature and hexagonal structure. Increasing the Cu doping ratio and annealing temperature improve the (1 0 1) preferential orientation. The crystallite size is ranged from 23.82 to 32.11 nm. XRD and FTIR reveal the formation of CdO in the 6% Cu-doped CdS film annealed at 400 °C and in all films annealed at 500 °C. The pure CdS film is of a porous structure and the close-packing and porosity of the films increase with increasing Cu%. Also, the pore diameter can be controlled from 50 to 15 nm with the increase of Cu content. The films showed transmittance below 70%. The optical band gap of the films is decreased from 2.43 to 1.82 eV with increasing Cu% and flow rate/deposition time. Additionally, the refractive indices and dispersion parameters of the films are also affected by the deposition conditions. Cu doping enhanced the films' photostability as well as the photocatalytic removal of methylene blue (MB).     

Deposition and characterization of pure and Cd doped SnO2 thin films by the nebulizer spray pyrolysis (NSP) technique

Pure and cadmium doped tin oxide thin films were deposited on glass substrates from aqueous solution of cadmium acetate, tin (IV) chloride and sodium hydroxide by the nebulizer spray pyrolysis (NSP) technique. X-ray diffraction reveals that all films have tetragonal crystalline structure with preferential orientation along (200) plane. On application of the Scherrer formula, it is found that the maximum size of grains is 67 nm. Scanning electron microscopy shows that the grains are of rod and spherical in shape. Energy dispersive X-ray analysis reveals the average ratio of the atomic percentage of pure and Cd doped SnO₂ films. The electrical resistivity is found to be 10² Ω cm at higher temperature (170 °C) and 10³ Ω cm at lower temperature (30 °C). Optical band gap energy was determined from transmittance and absorbance data obtained from UV–vis spectra. Optical studies reveal that the band gap energy decreases from 3.90 eV to 3.52 eV due to the addition of Cd as dopant with different concentrations.     

Improving carriers mobility in copper and iron-codoped CdO

Thin films of Fe and Cu-codoped CdO (CdO:Cu:Fe) with different Fe content and fixed Cu content were deposited in a high vacuum on glass and Si wafer substrates. These films were studied by X-ray fluorescence (XRF), X-ray diffraction (XED), optical spectroscopy, and dc-electrical measurements. The structural results show enhancement of film [1 1 1] orientation with Fe doping especially with 1.3%Fe film. Also, light doping with Fe improves the dc-conduction parameters of the CdO:Cu:Fe films so that the utmost enhancement of mobility (90.5 cm²/Vs) and conductivity (1470.6 S/cm) was found with 1.3 wt% Fe doping level. It was found that the variation in the bandgap is related to the variation in electron concentration that caused by Fe doping. For low Fe ion concentration (<1.3 wt% ), the bandgap varies according to the Moss–Burstein model.     

Evaluation of an Nd doping effect on characteristic properties of tin oxide

In the present work, transparent and conductive Nd doped SnO₂ thin films were deposited via spray pyrolysis. Crystallographic, morphological, optical and electrical characterizations of SnO₂ were researched as a function of Nd doping. The XRD analysis indicated the films had tetragonal cassiterite tin oxide structure and (211) preferential direction for NdTO-0, NdTO-1, NdTO-2 and NdTO-3 samples changed to (110) plane for NdTO-4 and NdTO-5 samples. The crystalline size and strain analysis were made by using a Williamson–Hall method. The SEM micrographs showed that all films had homogenously scattered pyramidal and small densely nanoparticles. The optical analysis indicated optical band gap value of undoped film increased with 1 at% Nd doping and then it decreased with more Nd content. The Hall measurements indicated that the highest electrical conductivity was obtained for 2 at% Nd doping content.     

Properties of nanostructured Al doped ZnO thin films grown by spray pyrolysis technique

Aluminium doped zinc oxide thin films were deposited on glass substrate by using spray pyrolysis technique. The X-ray diffraction study of the films revealed that the both the undoped and Al doped ZnO thin films exhibits hexagonal wurtzite structure. The preferred orientation is (002) for undoped and up to 3 at % Al doping, further increase in the doping concentration to 5 at % changes the preferred orientation to (101) direction. The surface morphology of the films studied by scanning electron microscope, reveal marked changes on doping. Optical study indicates that both undoped and Al doped films are transparent in the visible region. The band gap of the films increased from 3.24 to 3.36 eV with increasing Al dopant concentration from 0 to 5 at % respectively. The Al doped films showed an increase in the conductivity by three orders of magnitude with increase in doping concentration. The maximum value of conductivity 106.3 S/cm is achieved for 3 at % Al doped films.     

Effect of Al dopant concentration on structural,optical and photoconducting properties in nanostructured zinc oxide thin films

Thin films of undoped and doped ZnO, with different Al concentrations (1–5 wt%) were deposited onto glass substrates, by the sol–gel spin coating method. Grazing incidence X-ray diffraction (GIXRD) studies confirmed the nature of films as poly-crystalline, with typical hexagonal wurtzite structure. The films showed variation in crystallite size and change in relative intensities, upon different Al doping concentrations. The surface morphology of the films examined using FE-SEM, showed the grain size becoming smaller upon Al doping. The influence of Al with different concentrations, onto ZnO on the optical absorption and transmittance was studied using UV–Vis–NIR spectrophotometer in the wavelength range 300–2500 nm. The UV absorption shifted towards shorter wavelength upon Al doping. The average transmittance in the visible region increased for Al doped films up to 1–2 wt% and decreased for other concentration. The dark and photo conductivity measurements of the films indicated increase in the current values upon doping up to 1–2 wt% of Al and decreased for further concentrations. The rise and decay time measured from the photoresponse study, indicate larger values of rise time for the doped films compared to undoped ZnO. However, the film with 1–2 wt% doping of Al showed better response within the doping concentration. The thermal activation energy obtained from temperature-dependant conductivity showed decrease in the value upon Al doping up to 2 wt% and increased beyond this concentration in the temperature range 300–400 K.     

Using the acetylacetonates of zinc and aluminium for the Metalorganic Chemical Vapour Deposition of aluminium doped zinc oxide films

Metalorganic Chemical Vapour Deposition is a promising method for the growth of thin aluminium doped zinc oxide films (ZnO:Al), a material with potential application as transparent conducting oxide (TCO), e.g. for the use as front electrode in solar cells. For the low-cost deposition, the choice of the precursors is extremely important. Here we present the deposition of quite homogeneous films from the acetylacetonates of zinc and aluminium that are rather cheap, commercially available and easy to handle. A user-made CVD-reactor activating the deposition process by the light of halogen lamps was used for film deposition. Well-ordered films with an aluminium content between 0 and 8% were grown on borosilicate glass and Si(100). On both types of substrate, the films are crystalline and show a preferred orientation along the (002)-direction. The 0.3 to 0.5 μm thick films are highly transparent in the visible region. The best films show a low electric resistivity between 2.4 and 8 mΩ cm.