Nanostructured CdO Thin Films Research Articles

Detailed investigation of optical linearity and nonlinearity of nanostructured Ce-doped CdO thin films using Kramers–Kronig relations

Sol–gel-assisted spin coating technique has been employed to deposit Ce-doped cadmium oxide films (CdO) thin films on a glass substrate. Structural analysis carried out by XRD revealed that the films are polycrystalline and crystallize in a cubic structure. The preferential directions for the CdO growth are (2 0 0), and (2 1 0) and doping of Ce ions inhibits the growth. In addition to XRD, Raman analysis also supports the crystalline phase with no impurities. Using the Kramers–Kronig relations, the dispersion relation is evaluated from which the refractive index and the absorption coefficient were derived. The deposited doped and pure CdO films are highly transparent. The energy gap values of pure and doped CdO films are in the range of 2.2–4.2 eV, making them suitable for optoelectronic applications. The lower values of ‘n’ and ‘k’ are making the films most significant. The dielectric constant and nonlinear optical properties showed an increasing tendency on doping Ce ions into CdO films.

Realization of improved Hackee’s quality factor and photo degradation efficiency of cauliflower shape nanostructured CdO thin films through Cs doping

Cauliflower shape nanostructured Cs-doped CdO (CdO:Cs) thin films were grown using perfume atomizer. A strong (1 1 1) preferential orientation is noticed for the cubic structured CdO:Cs thin films. Surface morphology of CdO was strongly influenced with Cs doping. All the doped films exhibit better transparency than pure CdO. With Cs doping, the absorption edge seems to shift towards lower wave lengths (i.e. higher energies). The 2 wt.% Cs-doped CdO thin film exhibits a minimum resistivity of 0.95 × 10−3 Ω-cm. Increased Hackee’s quality factor realized with Cs doping confirms that the CdO:Cs thin films are well suited for optoelectronic devices especially as transparent electrodes. A maximum photo degradation efficiency of 86.9 % was realized for the 2 wt.% Cs-doped CdO thin film against malachite green under visible light.

Structural, morphological and optical properties of CdO nanostructures synthesized by chemical bath deposition method

In the present work, we have successfully synthesized CdO nanostructures with various molar concentrations by a two-step chemical method. The crystal structure of our nanostructured CdO thin films is cubic phase while the microscopic images show the formation of nanoparticles, spindles, and coconut fiber bark shaped CdO nanostructured films. These different structures were achieved merely by controlling the molar concentration of cadmium nitrate tetrahydrate and hexamethylenetetramine. The size of the CdO nanostructure slightly increases monotonically with molar concentration. Our chemical synthesis approach is inexpensive, reproducible and scalable.

Post-Annealing Effects on Surface Morphological, Electrical and Optical Properties of Nanostructured Cr-Doped CdO Thin Films

Nanostructured Cr-doped CdO thin films were deposited on glass substrates by reactive direct current magnetron sputtering and post-annealed in vacuum from 200°C to 500°C. X-ray diffraction studies confirmed that the films exhibit cubic nature with preferential orientation along the (111) plane. The crystallite size, lattice parameters, unit cell volume and strain in the films were determined from x-ray diffraction analysis. The surface morphology of the films has been characterized by field emission scanning electron microscopy and atomic force microscopy. The electrical properties of the Cr-doped CdO thin films were measured by using a four-probe method and Hall effect system. The lowest electrical resistivity of 2.20 × 10−4 Ω cm and a maximum optical transmittance of 88% have been obtained for the thin films annealed at 500°C. The optical band gap of the films decreased from 2.77 eV to 2.65 eV with the increase of annealing temperature. The optical constants, packing density and porosity of Cr-doped CdO thin films were also evaluated from the transmittance spectra.

Selectivity of Organic Vapour for Nanostructured CdO Thin Films Prepared by Sol–Gel Dip Coating Technique

Selectivity of Organic Vapour for Nanostructured CdO Thin Films Prepared by Sol–Gel Dip Coating Technique

Nanostructured CdO thin films for water treatments

CdO was the very first transparent conducting metal oxide discovered. CdO thin films show electrical and optical properties of interest as photosensitive anode materials for photochemical cells, phototransistors, photodiodes, window electrodes in liquid crystal displays, IR detectors, antireflection coatings, gas sensors and in other solar energy applications. In the present study we report on the spectroscopic, microscopic, electrical and photo-catalytic properties of CdO thin films prepared by a metal organic chemical vapor method. The degenerate semiconducting CdO thin films are useful as photocatalysts for water treatments.

Characteristic analysis on the physical properties of nanostructured Mg-doped CdO thin films—Doping concentration effect

Highly conductive and transparent magnesium-doped cadmium oxide (CdO:Mg) thin films have been deposited on suitably cleaned glass substrates maintained at 375°C by spray pyrolysis technique using perfume atomizer. The magnesium content in the films is varied from 0 to 8at% in steps of 2at%. The effect of Mg doping on the structural, morphological, optical and electrical properties of the CdO thin films has been studied. All the films exhibited cubic structure with a preferential orientation along the (111) plane irrespective of the Mg doping level. SEM analysis showed that the film morphology modifies from spherical shaped grains to closely packed cauliflower shaped nanostructures with Mg doping. Except for the film coated with 2at% Mg dopant, all the other doped films exhibited a blue shift in the optical band gap. Electrical studies revealed that the CdO:Mg film coated with 8at% Mg dopant had a minimum resistivity of 0.0853×101Ω-cm.

Nanostructured CdO Thin Films for LPG and CO<sub>2</sub> Gas Sensor Prepared by Spray Pyrolisis Technique

Nanostructured CdO thin films were deposited by spray pyrolysis techniques at different spray deposition time on glass substrates. Nanostructured CdO thin films was prepared using 0.05 M of cadmium acetate dehydrate (CH3COO) 2Cd·2H2O) was dissolved in the deionised water. These thin films were annealing in air at temperatures 500 °C for 60 min. The thickness of the films, crystallite and grain size were observed to increase with the increase in spray deposition time. As prepared thin films were characterized using XRD, FE-SEM and EDAX. The XRD analysis shows that CdO films were cubic structured. The electrical and gas sensing properties of these films were investigated. Prepared nanostructure CdO thin films show LPG (S = 1600) and CO2 (S = 435) gas response at different operating temperature. Gas response, selectivity, response and recovery time of the sensor were measured and presented.

Nanostructured CdO Thin Films for LPG and CO<sub>2</sub> Gas Sensor Prepared by Spray Pyrolisis Technique

Nanostructured CdO thin films were deposited by spray pyrolysis techniques at different spray deposition time on glass substrates. Nanostructured CdO thin films was prepared using 0.05 M of cadmium acetate dehydrate (CH3COO) 2Cd·2H2O) was dissolved in the deionised water. These thin films were annealing in air at temperatures 500 °C for 60 min. The thickness of the films, crystallite and grain size were observed to increase with the increase in spray deposition time. As prepared thin films were characterized using XRD, FE-SEM and EDAX. The XRD analysis shows that CdO films were cubic structured. The electrical and gas sensing properties of these films were investigated. Prepared nanostructure CdO thin films show LPG (S = 1600) and CO2 (S = 435) gas response at different operating temperature. Gas response, selectivity, response and recovery time of the sensor were measured and presented.

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 2.5h 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 370K 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.

Correlation between morphology and electro-optical properties of nanostructured CdO thin films: Influence of Al doping

Al doped cadmium oxide thin films have been deposited on glass substrates by sol–gel dip coating method with precursor solutions having different Al concentrations. The content of aluminum in the sol was varied from 0 to 5at.%. X-ray diffraction, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), UV–Visible spectroscopy and Hall effect analyses have been used to determine correlations between the film microstructure and the optoelectronic properties. X-ray diffraction analyses, clearly established that the crystallinity deteriorates by Al doping. Crystallite size calculations based on Debye Scherrer formula indicated that the CdO crystallite size decreases with Al content (from 37 to about 11nm). SEM and AFM were applied to study the morphology and to estimate the surface roughness of the obtained films. All films were very smooth, with a characteristic spherical grain size depending on Al content. The Root Mean Square (RMS) roughness of the films varied from 4.05 to 4.35nm with increasing Al concentration. The AFM images were also used for the analysis of the fractal behavior of the films. Doping with Al increased the films' optical transparency in the visible region and their conductivity.

Microstructural and Electrical Properties of Mn Doped Nanostructured CdO Thin Films

Microstructural and Electrical Properties of Mn Doped Nanostructured CdO Thin Films

Effect of Doping on Thermoelectric Property of Spray Deposited Nanostructured CdO Thin Films

Effect of Doping on Thermoelectric Property of Spray Deposited Nanostructured CdO Thin Films

Preparation of nanostructured Bi-doped CdO thin films by sol–gel spin coating method

The nanostructured Bi-doped CdO thin films were prepared using sol–gel spin coating method. The morphology and optical properties were investigated using atomic force microscopy (AFM) and UV visible spectroscopy. The AFM results indicate that the CdO films are formed from the nanoparticles and the grain size of the films is changed with bismuth doping level. The optical band gap values of undoped and Bi-doped CdO films were determined by optical absorption method. The band gap value of undoped CdO film was found to be 2.589eV, on the other hand, the band gap values of Bi-doped CdO films were found to be in the range of 2.657–2.684eV. The band gap value of the CdO films is increased with the content of Bi dopant. It is evaluated that the optical band gap and grain size of the CdO film could be controlled by Bi-doping.

Surface morphology and optoelectronic studies of sol–gel derived nanostructured CdO thin films: heat treatment effect

Morphological dependence of the optoelectronic properties of sol–gel derived CdO thin films annealed at different temperatures in air has been studied. After preparing, the films were investigated by studying their structural, morphological, d.c. electrical and optical properties. X-ray diffraction results suggest that the samples are polycrystalline and the crystallinity of them enhanced with annealing temperature. The average grain size is in the range of 12–34 nm. The root mean square roughness of the films was increased from 3.09 to 6.43 nm with annealing temperature. It was observed that the electro-optical characteristics of the films were strongly affected by surface roughness. As morphology and structure changed due to heat treatment, the carrier concentration was varied from 1.13 × 1019 to 3.10 × 1019 cm−3 with annealing temperature and the mobility increased from less than 7 to 44.8 cm2 V−1 s−1. It was found that the transmittance and the band gap decreased as annealing temperature increased. The optical constants of the film were studied and the dispersion of the refractive index was discussed in terms of the Wemple–DiDomenico single oscillator model. The real and imaginary parts of the dielectric constant of the films were also determined. The volume energy loss increases more than the surface energy loss at their particular peaks.

Optical and Structural Studies of Sol-Gel Deposited Nanostructured CdO Thin Films: Annealing Effect

C. The characterization of samples was carried out by X-raydiffraction,scanningelectronmicroscopyandUV-VISspectroscopy. Resultsshowthatthesamplesarepolycrys-talline in nature and the crystallinity of the films improves with temperature. The average grain size is in therangeof19–34nm. Itwasobservedthattheopticalparametersofthefilmswereaffectedbyannealingtemperature.PACS:78.20.Ci,78.66.Li,78.67.–n,81.20.Fw