Cadmium Oxide Thin Films Research Articles

Optical properties of CdO thin films

Cadmium Oxide thin films were deposited on glass substrate by spray pyrolysis technique at different temperatures (300,350,400, 500)oC. The optical properties of the films were studied in this work. The optical band-gap was determined from absorption spectra, it was found that the optical band-gap was within the range of (2.5-2.56)eV also width of localized states and another optical properties.

Nebulized spray pyrolysis deposited CdO thin films for liquefied petroleum gas and ethanol gas sensor

High quality cadmium oxide (CdO) thin films were prepared through an inexpensive and simple nebulized Spray Pyrolysis (neb-SP) technique. The transparent conducting CdO thin films deposited at different substrate temperatures (TS) for the ethanol and liquefied petroleum gas (LPG) sensor application. XRD, SEM, UV–vis Spectroscopy and Hall Effect were done to study the structural, morphological, optical and electrical properties respectively. Polycrystalline nature thin films shows (1 1 1) cubic structure as the prominent peak. Surface morphology studies reveal that the grain size and roughness of the films are increased with increase in the substrate temperature. The average transmittance of the yellowish transparent CdO thin films is about 57%, thus the films are transparent in the visible region. The optical band gap (Eg) value of the CdO films increased from 2.16 to 2.28 eV with increase in the TS from 225 °C to 300 °C. The minimum value of electrical resistivity of the films is 1.40 × 10−3 Ωcm obtained at 275 °C. The neb-SP deposited CdO thin film (275 °C) shows maximum response to the ethanol and LPG gas sensitivity of 31.87% and 16.4% respectively at operating temperature of 573 K. Thus the results authenticate that the CdO thin films deposited low substrate temperature with high quality can be achieved via neb-SP technique compared to other wet chemical or physical method.

Conversion of preferred crystalline orientation by annealing and its impacts on the structural, electronic, and optical properties of pulsed laser-deposited CdO thin films

The impact of annealing on the preferred crystalline orientation as well as the structural, electronic, and optical properties of pulsed laser-deposited 150 ± 3 nm thick cadmium oxide (CdO) films was studied. X-ray diffraction analysis revealed that the annealed CdO films have smaller crystallite sizes, as their molecules at the grain boundaries possessed enough kinetic energy to rearrange their preferred crystalline orientation between (111) and (200). The atomic force microscopy and field emission scanning electron microscopy analyses revealed an enhancement in the active surface area with optimized grain boundaries by annealing which facilitates gas adsorption/desorption. DC electrical conductivity depends on the annealing process and reveals two different conduction mechanisms. The direct optical energy gap was decreased from 3.41 eV to 2.76 eV by annealing at 473 K which is greater than the theoretical value, i.e. 2.2 eV, for bulk CdO. The findings agree with the Burstein-Moss effect as a result of the increased carrier concentration following the generation of numerous oxygen vacancy sites and Cd interstitials. However, mutual charge carrier-impurity interaction and charge carrier Columb interaction contributed to narrowing the band gap by increasing the annealing temperature. The enhanced values of Urbach energy, optical packing density, dispersion parameters, optical conductivity, dissipation factor, oscillator strength, and lattice dielectric constant supported the effectiveness of the annealing process on tailoring optoelectronic responses in the infrared region for the CdO thin films for use in optoelectronic devices. Moreover, the calculated linear optical susceptibility, and nonlinear constants (i.e. third-order optical susceptibility and nonlinear refractive index) were the highest for CdO films annealed at 473 K. The improved value of the figure of merit, solar material protection factor, and solar skin protection factor for the CdO films, annealed at 473 K supports its use in several photovoltaic applications, including solar cells.

Influence of multi-doping (Zn and Sn) on the optical, and electrical properties of spray-deposited CdO thin films

This investigation has been focused on the spray-deposited pure cadmium oxide (CdO) thin films and also doped with zinc (Zn) and tin (Sn), as a transparent conducting oxide for optoelectronic applications. By varying the concentration of Sn (0–2%) into CdO, the microstructural, morphological, and optoelectronic properties were investigated. XRD spectra confirmed the polycrystalline cubic structure of the pure, doped, and co-doped CdO films. SEM investigation reveals the crack-free homogeneous cauliflowers-like morphology of the fabricated thin films. The existence of elemental compositions such as Cd, Zn, Sn, and O in the prepared films was confirmed by EDS analysis. All of the doped and co-doped CdO films showed good transparency in the visible range. Moreover, a slight increment has been found in the optical band gap from 2.43 eV to 2.50 eV with increasing Sn concentration, which can be explained by the Burstein-Moss phenomena. A decrement of Urbach energy was noted for an increased concentration of Sn. Besides, Zn and Sn (1 %) co-doped films exhibited the lowest electrical resistivity value 4.09×10−4 Ω-cm among other doped compositions. However, the addition of Zn and Sn into CdO thin films enhanced the optoelectronic properties.

Tailoring epsilon-near-zero wavelength and nonlinear absorption properties of CdO thin films by Mo doping

Cadmium oxide (CdO) has recently attracted attention as a material with controllable properties tailored for optoelectronic and nanophotonic devices due to its superior mobility. However, its potential application in near-infrared (NIR) remains to be explored. In this work, we demonstrate that the epsilon-near-zero (ENZ) wavelength and nonlinear optical properties of CdO films can be effectively tuned by Mo doping. The results show that Mo doping increases the electron concentration as well as improve the crystalline quality of CdO. With increasing Mo doping, we achieve blueshifts of the ENZ wavelength from 2.89 to 1.56 μm. The nonlinear absorption (NLA) behavior at 1550 nm changes from reverse saturable absorption to saturable absorption with increasing Mo content. Moreover, significant improvement in NLA performance with nonlinear absorption coefficient β = −72 cm/GW is observed at the highest doping content. Our work shows that doped CdO films with tunable optoelectrical and nonlinear optical properties can be an ideal candidate for optoelectronic and nanophotonic application in the NIR region.

Synthesis and characterization of Cr-doped cadmium oxide thin films for NH3 gas-sensing applications

Synthesis and characterization of Cr-doped cadmium oxide thin films for NH3 gas-sensing applications

Structure, optical properties, and electrical properties of low copper-doped cadmium oxide thin films for optoelectronic applications

Structure, optical properties, and electrical properties of low copper-doped cadmium oxide thin films for optoelectronic applications

INVESTIGATION OF OPTICAL AND STRUCTURAL PROPERTIES OF CDO AND CDO: CU PREPARED BY LASER-INDUCED PLASMA

In this research, thin films of cadmium oxide (CdO) and cadmium oxide doped with pure copper (CdO: Cu) attracted a lot of attention due to their applications in electronic and optical devices. Thin films were adopted in this work that were deposited on substrates made of glass using laser-induced plasma technology at (1064nm, 6x10-2mbr, and 6 Hz ) in vacuum conditions, where the plasma formed as a result of the pulsed laser is used to transfer and deposition the film on the glass substrates, then the prepared films are annealed at a temperature of 500 degrees Celsius. The purity of the material was confirmed by taking the crystal structure of X-ray diffraction. The optical properties of the thin films of cadmium oxide (CdO) and cadmium oxide doped with copper (CdO: Cu) were analyzed by drawing the relationship between (αhυ)1/2 against the two-photon energy curves and found that the energy gap is 2.5. eV for the cadmium oxide CdO film, and you noticed that the energy gap decreases when the pulse increases, but in the case of tarnishing with copper, the energy gap decreased from 2.5 eV to 2.4 eV, and it suffers from a greater decrease when the pulse increases

The effective role of potassium doping in improving the structural, morphological optical, and electrical properties of CdO thin film for optoelectronic application

Aspiring to increase the electrical conductivity, enhance the electron mobility, and widen the band gap, potassium (K) was used as a substitutional dopant in the CdO matrix. Transparent cadmium oxide (CdO) and potassium-doped cadmium oxide (K–CdO) thin films with different K concentrations (0.02, 0.04, and 0.06 mol) were deposited on glass substrates via thermal evaporation technique. A remarkable shift of (111) peak towards high Bragg's angle was noticed as the potassium content was increased, which established the successful incorporation of K into the CdO matrix. The surface became more compacted and denser with a noticeably smaller particle size upon doping with K, as revealed by field emission scanning electron microscopy (FESEM)aand the Willmason-Hall plot. The optical band gap was boosted from 2.5 to 2.79 eV, when the K concentration was increased from 0.0 to 0.06 mol. Moreover, the optoelectronic features, such as transmittance, reflectance, skin depth, refractive index, tailing energy, optical dielectric constants, and optical conductivity were investigated in depth. The Hall experiment was used to determine the DC electrical properties of the K– CdO film including the resistivity (ρ), Carrier concentration, Carrier mobility, and Hall coefficient. The Hall measurement asserted that the film is an n-type semiconductor and electron mobility (μn) was boosted, as the K concentration was raised. The increased optical band gap and enhanced electron mobility achieved by potassium doping reflected the fact that K-doped CdO thin films are promising window layers in photovoltaic applications.

Nano-Crystalline Cadmium Oxide Thin Films for Supercapacitor Application: Effect of Solution Concentrations

Nano-Crystalline Cadmium Oxide Thin Films for Supercapacitor Application: Effect of Solution Concentrations

Structural and optoelectronic properties of nickel doped CdO thin films deposited by spray pyrolytic technique

In this work, Cadmium oxide (CdO) and Nickle (Ni) doped cadmium oxide (CdO: Ni) thin films have been fabricated onto glass substrate by spray pyrolysis technique. The undoped and Ni-doped CdO thin films have been deposited at 400 °C heated glass substrate. The films' structure, morphology and optical properties were investigated & analyzed as a function of Ni doping level. As confirmed by different characterization, the preparade films have polycrystalline with cubic structure. Based on the results, the pure CdO films showed sharper and more intense diffraction patterns than Ni-doping films. Compared to the pure CdO films, the average grain size of the doped films decreases with increasing of doping level. Furthermore, the optical properties of Ni-doped CdO thin films showed lower absorption coefficient than pure films. However, the higher transparency of Ni-doped CdO films in the visible region consider a good window for the most optoelectronic devices applications. The energy band gap was tuned via Ni doping impurities and it increases as doping level increases.

Studying the Optical and Structural Properties of Cadmium Oxide Thin Films Prepared by Successive Ionic Layer Adsorption and Reaction (SILAR) Technique

Studying the Optical and Structural Properties of Cadmium Oxide Thin Films Prepared by Successive Ionic Layer Adsorption and Reaction (SILAR) Technique

Investigating the influence of Eu-doping on the structural and optical characterization of cadmium oxide thin films

In the present investigation, a low-cost and high-operational sol-gel spin coating technique for preparing undoped and various Europium (Er)-doped CdO films of molar percentages of 1%, 5%, 10%, and 15% were considered. Using X-ray diffraction, the polycrystalline nature reveals two preferred orientations of (111) and (200). The mean crystallite size was evaluated and increased from 20.95 to 49.37 nm using the well-known Scherer’s formula by increasing the Eu- dopant content. The atomic force microscopy images indicate a homogeneity of a granular distribution deteriorated with Eu-content. The root means square roughness value was evaluated and increased from 4.1 nm to 284 nm with Eu-doping. High transmission of approximately 80% in the visible region spectrum was recorded. The optical band gaps are increased from 2.2 to 2.46 eV from the undoped and various Eu-content %. A relationship between the Eu- content % for CdO films and the optical parameters was discussed to support the availability of the device for optoelectronic applications.

The effect of copper doping on the structural, optical, and electrical properties of cadmium oxide thin films deposited by the spray pyrolysis technique

The effect of copper doping on the structural, optical, and electrical properties of cadmium oxide thin films deposited by the spray pyrolysis technique

Effect of Indium Doping on Structural Properties of Spray Pyrolysed Cadmium Oxide Thin Films

Pure films of cadmium oxide and indium-doped cadmium oxide films were deposited using a spray pyrolysis technique. The deposited films were structurally characterised using the X-ray diffraction method. The structural studies revealed that films are polycrystalline in nature with a cubic lattice. The decrease in particle size from 42 nm to 34 nm was observed as dopant was introduced. For pure CdO thin films, the band gap energy obtained was of the order of 2.58 eV, and it decreased to 2.32 eV with the addition of dopant.

Effects of transition metal dopants (Mo and W) on electrical and optical properties of CdO thin films

Cadmium oxide (CdO) is known to have the highest electron mobility among common transparent conductive oxides (TCOs). Here, we carried out a systematic investigation on the properties of CdO films doped with transition metal donors, namely Mo (CMO) and W (CWO) which have been reported to enhance the mobility in In2O3. We find that the electron concentration N in as-grown CMO and CWO increases with dopant concentration to> 1021 cm−3. While the mobility μ increases with rapid thermal annealing (RTA) temperature, N decreases when the temperature is> 400 °C, suggesting that Mo and W are unstable donors. The stronger affinity of the Mo and W to diffuse out in an O2 environment results in an even stronger decrease in N when annealed in O2. Isothermal RTA at 300 °C further reveals that H interstitial donors incorporated during room temperature film growth are unstable at temperature< 300 °C. Overall, both CMO and CWO can achieve a low resistivity of ∼1.5 × 10−4 Ω-cm with μ > 100 cm2/V-s and N∼3.5 × 1020 and 4 × 1020 cm–3, respectively, as well as an overall transmittance> 80% up to λ > 1600 nm with x ≲ 0.01 after RTA at 600 °C in N2. Finally, changes in optical absorption edges Eopt of CMO and CWO are consistent with the modification of the conduction band (CB) due to anticrossing interactions of the dopant d–states with the CdO CB, which also flattens the CB dispersion which dramatically lowers the μ at high x.

Dislocations and crystallite size distribution of cadmium oxide thin films synthesized by spray pyrolysis technique

Cadmium oxide (CdO) thin films have been successfully deposited on amorphous glass substrates by spray pyrolysis technique at a temperature, 573 °K using aqueous solution of cadmium nitrate 4-Hydrate powder with a concentration of 0.1 M. The X-ray diffraction (XRD) studies have revealed that the films exhibit cubic crystal structure. The modified Williamson–Hall and Warren–Averbach methods are used successfully for analyzing the XRD line profile for determining the crystallite size, dislocation densities and crystallite size distribution in CdO thin films. The crystallite size (D) and integral breadths (d) (D = 44.139 nm and d = 32.237 nm) are obtained by the modified Williamson Hall, while the area-weighted average grain sizes and volume-weighted obtained of modified Warren–Averbach method are xvol=46,06nm andxarea=29,7nm, respectively. The size parameter (Lo), dislocation density (ρ), effective outer cut-off radii (Re) and dislocation arrangement parameter (μ) gotten of Warren–Averbach are 35.53 nm, 2.0 × 1015 m−2, 7 nm and 0.31 nm, respectively. The particle size distribution (x) derived of XRD and estimated of size parameter is the size distribution function f(x) of log-normal.

Spray-Deposited Rare Earth Metal Ion (Sm3+, Ce3+, Pr3+, La3+)-Doped CdO Thin Films for Enhanced Formaldehyde Gas Sensing Characteristics.

This study shows the electrical conductivity-dependent gas sensing characteristics of spray-deposited rare earth (RE) metal ion (Sm3+, Ce3+, Pr3+, La3+)-doped cadmium oxide (CdO) thin films on soda-lime microscope glass substrates at 300 °C. We examined the deposited films’ structural, surface microstructural, DC electrical, and gas sensing features. The X-ray diffraction study indicates that all samples were polycrystalline, with the favored growth direction shifting from the (111) plane to the (200) plane. The highest root-mean-square values were obtained for the Pr-doped CdO thin film (5.86 nm). The surface microstructure of CdO thin films was significantly influenced by the RE metal ion dopant, with typical grain size values ranging from 64 nm to 134 nm depending on the dopant. The carrier concentration and resistivity of CdO films vary based on the RE metal ions used as dopants. Low resistivity (3.01 × 10–4 Ω.cm) was achieved for the CdO thin film doped with La. High gas sensitivity (71.42%) was achieved for CdO thin films doped with La. The donor dopant regulated the electrical conductivity and gas sensing capabilities of CdO thin films.

Effect of Annealing Time on Structure, Morphology, and Optical Properties of Nanostructured CdO Thin Films Prepared by CBD Technique

Nanostructured cadmium oxide (CdO) thin films were deposited onto glass substrates using the chemical bath deposition (CBD) technique. Different deposition parameters such as deposition time, bath temperature, pH, and CdSO4 concentration have been considered to specify the optimum conditions to obtain uniform and well-adherent thin films. The thin films prepared under these optimum conditions were annealed for different times (20, 40, and 60 min) at 300 °C, where no previous studies had been done to study the effect of annealing time. The XRD analysis showed that the as-deposited film is Cd(OH)2 with a hexagonal phase. While all the annealed films are CdO with a cubic phase. The crystallite size increases with the annealing time. However, the strain, dislocation density, and the number of crystallites were found to be decreased with annealing time. SEM images of annealed films showed a spherical nanoparticle with an average of particle size 80–46 nm. EDX analysis revealed that the ratio of cadmium to oxygen increases with increasing the annealing time to 40 min. The optical characterization shows that the transmittance is in the range of 63–73% and the energy gap is in the range of 2.61–2.56 eV. It has been found that the transmittance increased and the energy gap decreased with the annealing time. The prepared CdO films can be used in photodegradation applications to remove pollutants from water.

Preparation and nonlinear optical characterization of Flourine-doped cadmium oxide thin films

Undoped CdO films and three different molarities of cadmium oxide (CdO) films were doped with fluorine on glass slides via a chemical spray pyrolysis method. The samples were analyzed using X-ray diffractometry (XRD), scanning electron microscopy (SEM), UV–VIS-NIR spectroscopy, electrical measurements, and Z-scan measurements. XRD measurement revealed better crystallinity with preferred orientation at [111] plane. Nanospheres of varying sizes were obtained from the surface micrographs. The direct band gap energy decreased as the fluorine concentration increased. The film resistivity recorded a decline with increased carrier mobility as the flourine concentration increased. The nonlinear optical absorption coefficient (β) gotten for 0.0003 M, 0.0004 M, and 0.0005 M at 632.8 nm wavelength are 3.83×10–3 m/W, 5.7 × 10–3 m/W and 5.48×10–3 m/W respectively. The deposited films find potential application in solar cell and optoelectronic devices.