CdO Films Research Articles

Influence of doping fluorine on the structural, surface morphological and optical properties of CdO films

CdO and CdO:F films were prepared by ultrasonic spray pyrolysis method on glass substrates at temperature of 250 ± 5 °C. The structural and optical properties of pure and fluorine doped CdO films were characterized by XRD measurements and UV–VIS spectra, respectively. X-ray diffraction patterns show that the films have the polycrystalline structure with preferred orientation along (111) plane. Scherrer Method and Williamson Hall Method were used for calculating of the crystalline grains and strains of films. It is observed that the films at 8% F doped has better crystallinity level, and F doping decreases the defects in CdO films and improves crystallite quality. By UV–VIS spectra, it is revealed that the film with 8% F doped has a high transmittance about 65% in the visible region together with a direct band gap of 2.70 eV. Thicknesses, refractive indices and extinction coefficient values are determined by spectroscopic ellipsometry technique using Cauchy–Urbach model.

Investigations on the thickness dependent structural, morphological, and optoelectronic properties of sprayed cadmium based transparent conducting oxide

The influence of thickness on the properties of cadmium oxide thin films deposited using simple and cost-effective chemical spray pyrolysis technique is studied. The maximum film of thickness 2752nm is achieved by tuning spraying parameters. The thickness dependent structural, morphological, and optoelectronic properties of CdO thin films have been investigated in detail. The microstructure of CdO thin films significantly changed from rough to smooth and further to rougher surface with increase in film thickness. This behavior has been further confirmed from water contact angle measurement. The optical studies show that the direct band gap energy values ranging between 2.23 and 2.46eV. The Hall effect measurement indicates that all the films exhibit n-type semiconducting behavior with their electrical resistivity lies in the range of 12.8×10−4 to 3.7×10−4Ω·cm. The CdO film with thickness of 1371nm exhibited the best optoelectronics properties (transmittance of 74%, figure of merit of 18.23×10−3(Ω)−1, carrier concentration of 7.30×1020/cm3 and mobility of 23.11cm2/Vs) among all the films.

Optical and magnetic properties of CdO thin films doped with Ba2+ (cation) ions

Ba-doped CdO (CdO:Ba) thin films with different concentrations of Ba (0, 1, 2 and 3 wt.%) were prepared on glass substrates by spray technique using perfume atomiser. The effect of Ba doping concentration on the structural, morphological, optical, photoluminescence and magnetic properties of the CdO films was investigated and the results obtained are presented in this work. Structural studies support the polycrystalline nature of the films. The direction of preferential growth of the CdO film along the (1 1 1) plane remain unaltered with Ba doping. Morphological studies show the presence of cauliflower-shaped structures for all the films. The optical transparency seems to be enhanced for the Ba-doped CdO films. The doped films exhibit ferromagnetic behaviour. The obtained results infer that barium, a cationic dopant ion, can enhance the optical and magnetic properties of CdO thin films.

Effects of concentration on CdO films grown by electrodeposition

Thin films of CdO were synthesized by electrodeposition via chronoamperometry. The concentrations of aqueous solutions of Cd(NO3)2 were chosen between 0.005 and 0.08 M. It was thought that the reaction rate would reach saturation at 0.02 M of concentration and it was measured as the concentration increased, the thicknesses of the films increased from the 452 nm to the 798 nm. The well-crystallized film was observed to be at 0.01 M of concentration. It was also found that the band gap increased at low concentrations and surface morphology of the films did not change much with concentration.

Mechanical and tribological behavior of sol–gel TiO2–CdO films measured at the microscale levels

In this work, we present a mechanical and tribological study at the microscale of sol–gel TiO2–CdO films, which are used in photocatalytic applications. The films were deposited as a good-quality polycrystalline material with majority of CdO or CdTiO3 phases depending on their Ti/Cd concentration ratios. Films with the majority of CdTiO3 phase presented the highest hardness and lowest plastic deformation during the indentation tests. The evolution of wear, friction coefficient, and roughness on the films was quantitatively studied by multiple-passes measurements on a depth-sensing instrumented indentation system. These measurements allowed us to observe the films’ wear mechanisms and correlate them with their microstructure and mechanical properties. To compare the crystal structure, mechanical properties and tribological behavior of these films, we also analyzed sol–gel CdO and TiO2 films deposited under similar conditions.

Influence of sol concentration on CdO nanostructure with gas sensing application

The effect of sol concentration has been investigated on the sol-gel derived CdO nanostructures to optimize the optical and electrical properties enhancing gas sensing properties at low temperatures. X-ray diffraction patterns show that 0.5M CdO film has cubic structure (111) preferred orientation with 34nm particle size. Scanning electron micrographs indicated concentration dependent surface morphology. The optical band gap energy for highly transparent thin films increases from 1.9eV to 2.34eV as molarity was increased from 0.2M to 1.0M. The photoluminescence spectra of the samples have a violet to blue emission peak centred at 435nm. J-V characteristics show that thin film of 0.5M has conductivity 1.41×10−3S/m. The sensor characteristic such as response curve, sensor response, response time and recovery time were measured for optimized thin film at different operating temperatures. The sensor response was found 20% near room temperature (32°C) and proportional to temperature. Fastest response time 10s and recovery time 20s were observed near room temperature. The resistivity of sensor was found to decrease in presence of gas attribute to more charge carriers with flower like morphology. Our study is encouraging to get faster response by CdO thin films near room temperature.

The role of Triton X-100 as a surfactant on the CdO nanostructures grown by the SILAR method

Abstract In this work, the effect of surfactant Triton X-100 (TX-100) on structural, morphological and optical properties of nanostructured CdO films has been researched. Four series of nanostructured CdO films with TX-100 concentrations of 0.25–1.0 M% of the growth solution were prepared by the Successive Ionic Layer Adsorption and Reaction (SILAR) technique on glass substrates and were characterized by scanning electron microscopy, surface roughness, X-Ray diffraction and UV–Vis. Spectroscopy. Scanning electron microscopy exhibited that the particle thickness increased with increasing TX-100 content. Surface roughness (Ra) measurement exhibited that Ra value accordingly decreases in the presence of TX-100. From the X-Ray diffraction patterns it was calculated that the crystallite size of the films increased parallel to the particle size with increasing TX-100 content. UV results presented that the optical bandgap values of the film can be adjusted with TX-100 content where optical bandgap decreased with increasing TX-100 content in the growth bath. The results show that the amount of TX-100 in the growth bath played a significant mission in adjusting the main physical properties of the nanostructured CdO film.

Optoelectronic, magnetic and antibacterial properties of CdO thin films doubly doped with Mn (cationic) and F (anionic) ions

This paper outlines the effect of (Mn + F) double doping on the structural, morphological, optoelectronic, magnetic and antibacterial properties of CdO thin films. Undoped CdO, Mn-doped CdO and (Mn + F) doubly doped CdO films exhibit face-centered cubic structure with a strong (1 1 1) preferential growth. Crystallite size value of the undoped film estimated using the Scherrer formula decreases with Mn doping and with double doping it increases. Cauliflower shaped nanostructures are evinced from the SEM images. Increased optical transparency is observed for the doubly doped films. The optical band gap value of the Mn-doped CdO film is found to be red shifted and for the (Mn + F) doubly doped films it is blue shifted which may be attributed to the Moss-Burstein effect. Ferromagnetic ordering is observed for the doped films. The doped films show increased antibacterial efficiency against K. pneumonia a gram −ve bacteria. The obtained results infer that the CdO films doubly doped with Mn (cationic) and F (anionic) ions exhibited better optical, electrical, magnetic and antibacterial properties.

Structural and optical properties of thermally treated CdO thin films deposited on ITO coated glass substrates for photovoltaic applications

In this study, we have reported effects of post-deposition thermal treatment of cadmium oxide thin films on indium tin oxide coated glass substrates by sol–gel technique using spin coating method. To prepare CdO thin films, a precursor solution based on a derivative from cadmium acetate was gelated and subsequently coated on ITO/glass substrates. Spin coated CdO films were annealed in air at varied temperatures of 300, 400, and 500 °C. The crystallite size, microstrain and dislocation density were estimated from high resolution X-ray diffraction analysis. X-ray diffraction patterns confirmed cubic phase formation in polycrystalline CdO films. Cross-sectional and top surface morphology of the films was studied by field-enhanced scanning electron microscopy. The as-deposited and thermally treated CdO thin films for various annealing temperatures showed an increase in the optical transmittance to 79% from that of 63% of CdO film in the visible and near infrared region. Shrinkage in band gap from 2.6 to 2.4 eV was reported for temperature variation of 300–500 °C. The emission properties of as-deposited and thermally treated CdO thin films were studied by photoluminescence spectrum recorded at 298 K.

Surface Morphology and Opto-electronic Properties of Nanostructured Cr doped CdO Thin Films for Photovoltaics

CdO thin films doped with different concentrations of chromium were deposited on mica substrates by DC reactive magnetron sputtering method. The effect of Cr concentration (1% to 5%) on structural, electrical and optical properties of CdO films was investigated. The structural studies reveal that the films are polycrystalline with preferred orientation along (1 1 1) plane. From the FESEM micrographs, it was clearly seen that all the films have smooth and homogeneous surface morphology. The optical transmittance of 72% and minimum resistivity of 5.36 x 10-4Ω.cm is obtained for 4% Cr doped CdO thin films. The optical band gap of Cr doped CdO thin films increases from 2.72 to 2.81 eV with the increase of Cr concentration due to Burstein-Moss effect. The optical constants such as absorption coefficient (α), extinction coefficient (k) and refractive index (n) were determined from the optical transmission data.

Optical, Electrical, and Morphological Effects of Yttrium Doping of Cadmium Oxide Thin Films Grown by Ultrasonic Spray Pyrolysis

CdO films doped with Y concentrations of 0%, 1%, 2%, and 3% were deposited onto soda lime glass using ultrasonic spray pyrolysis. The effect of the doping level on the structural, morphological, optical, and electrical properties of the films was characterized. X-ray diffraction analysis was used to establish that all of the samples were polycrystalline and to determine the structural parameters, i.e., lattice spacing (d), phases and associated (hkl) planes, grain size (D), and dislocation density (δ). The films possessed high conductivity and carrier concentration, showing n-type semiconducting behavior. The films were almost transparent over the range from 600 nm to 1100 nm. The energy bandgap was 2.43 eV, 2.53 eV, 2.68 eV, and 2.70 eV for Y doping of 0%, 1%, 2%, and 3%, respectively. The refractive index and extinction coefficient of the films over the range from 700 nm to 1100 nm were determined by spectroscopic ellipsometry. Atomic force microscopy revealed the effect of Y doping on the surface morphology of the CdO films.

CdO Films Obtained by Electrodeposition at -0.5 V and -0.7 V Potentials Range

CdO Films Obtained by Electrodeposition at -0.5 V and -0.7 V Potentials Range

Double doping (Mn + Cl) effects on the structural, morphological, photoluminescence, optoelectronic properties and antibacterial activity of CdO thin films

The effects of (Mn+Cl) double doping on some physical properties and antibacterial activity of CdO thin films deposited by spray technique using a perfume atomizer is reported in this paper. XRD studies confirm the polycrystalline nature of the films. CdO:Mn and (Mn+Cl) doubly doped CdO thin films exhibit face-centered cubic structure similar to that of the undoped CdO film. Decreased transparency is observed for the Mn-doped CdO film which got enhanced for the (Mn+Cl) doubly doped films. Optical band gap exhibits a red shift for the CdO:Mn thin film and with (Mn+Cl) double doping it exhibits a blue shift which may be attributed to Moss-Burstein (MB) effect. Increased resistivity is observed for the Mn-doped CdO film and for the (Mn+Cl) doubly doped films it decreases. From the obtained results it is observed that CdO thin films doubly doped with Mn and Cl precursor ions exhibit better physical properties which make them suitable for future optoelectronic device applications. Antibacterial activities of the as deposited films were carried out against E. coli a gram negative bacteria and from the zone of inhibition it is confirmed that the (Mn+Cl) doubly doped CdO thin films can be used as a good antimicrobial agent against pathogenic microorganisms.

Effects of fluorine doping on structural, optical and electrical properties of spray deposited CdO thin films

Fluorine doped cadmium oxide (CdO:F) thin films were deposited onto glass substrates by spray deposition technique. Fluorine concentration dependent structural, optical and electrical properties of the films are reported. X-ray diffraction study confirms the growth of polycrystalline cubic CdO films. Optical absorption analysis of the films shows increase of optical band gap energy from 2.45 to 2.65 eV for the increase of fluorine concentration. The transparency of the films is found to be ≥ 80% and also it is increased with the fluorine concentration. Hall-Effect measurement of the films shows resistivity change between 2.5 × 10−4 and 4.5 × 10−4 Ω cm and carrier concentration in the range of 4 × 1015 cm−3 to 7 × cm−3 depending on doping concentration. Photoresponse study of the fabricated CdO:F/p-Si heterostructure diode is also studied and reported.

Optical and optoelectronic properties of morphology and structure controlled ZnO, CdO and PbO thin films deposited by electric field directed aerosol assisted CVD

A simple and convenient electric field directed aerosol assisted chemical vapor deposition method is developed for the deposition of morphology and structure controlled thin films of ZnO, CdO and PbO with enhanced visible light photoelectrochemical activity. The films are generated from commonly available metal acetates solution in THF at 400 °C. The FESEM/EDX, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, UV–Vis spectrophotometry was carried out to investigate morphology, structure, stoichiometry and optical band gap of the fabricated films. The photelctrochemical properties investigated in the presence of 0.1 M Na2SO4 of the as-produced ZnO, CdO and PbO thin films show current densities of 207, 263, 237 and 1.55, 215, 1.67 µA cm−2 in light and dark respectively. These results show a slight improvement in photocurrent density of the films prepared under the influence of electric field as compared to the films deposited in the absence of electric field. This difference may have arisen due to compact structure and uniform morphology created under the influence of electric field.

Electrical parameters of metal doped n-CdO/p-Si heterojunction diodes

The CdO, Al doped CdO and Cu doped CdO thin films were coated on p-type silicon substrates by sol–gel spin coating method. The structural, surface morphological and electrical properties of undoped, Al and Cu doped CdO films on silicon substrate were studied. The Ag/CdO/p-Si, Ag/Al: CdO/p-Si and Ag/Cu: CdO/p-Si heterojunction diodes were fabricated and the diode parameters such as reverse saturation current, barrier height and ideality factor of the diodes were investigated by current–voltage (I–V)characteristics. The reverse current of the diode was found to increase strongly with the doping. The values of barrier height and ideality factor were decreased by doping with aluminium and copper. Photo response of the heterojunction diodes was studied and it was found that, the heterojunction diode constructed with the doped CdO has larger Photo response than the undoped heterojunction diode.

Electro-optical properties of the metal oxide-carbon thin film system of CdO-LCC

This article presents the results of a study electrical and optical properties of the thin film system of CdO-LCC. Cadmium oxide films were obtained by method of thermal oxidation. CdO-LCC thin film system was produced by applying on a CdO film a linear chain carbon film in thickness of 100 nm using the ion-plasma method, after which the obtained system was annealed. The studies showed that the obtained CdO-LCC films are quite transparent in the visible region; it has polycrystalline structure, thickness around 300 nm, the band gap to 2.3 eV. The obtained thin film system has photosensitive properties.

Characterization of spray pyrolytically deposited high mobility praseodymium doped CdO thin films

Praseodymium (Pr) doped CdO thin films with high transparency and high mobility were deposited, using a homemade spray pyrolysis setup, on micro-slide glass substrates preheated at 300°C. Polycrystalline nature and Cd-O bond vibration of deposited films were confirmed by X-ray diffraction, micro-Raman and Fourier transform infrared spectroscopy analyses. The oxidation state of Cd2+, O2−, and Pr3+ was confirmed by X-ray photoelectron spectroscopy analysis. The highest average particle size (92nm-FESEM) and high RMS (13.48nm-AFM) values are obtained for 0.50wt% Pr doped CdO thin film. The optical band gap is varied between 2.38eV and 2.52eV, depending on the Pr doping concentration. Photoluminescence spectra revealed that Pr doped CdO thin film exhibits strong green emission at 582nm. High mobility (82cm2/Vs), high charge carrier concentration (2.19×1020cm−3) and high transmittance (83%) were observed for 0.50wt% Pr doped CdO film. A high figure of merit (9.79×10−3Ω−1) was obtained for 0.50wt% Pr doped CdO thin films. The mechanism behind the above results is discussed in detail in this paper.

Structural and optical properties of laser irradiated nano structured cadmium oxide thin film synthesized by sol-gel spin coating method

Cadmium oxide CdO nanostructured thin films are synthesized using sol-gel spin coating method. The prepared samples of CdO thin films are irradiated with 10 mJ laser from pulsed Q-Switched Nd:YAG laser at 1064 and 532 nm wavelength. The samples were exposed to 45 pulses of 7 ns pulse duration. Morphology and structural analysis were carried out with scanning electron microscope (SEM) micrographs and X-ray diffraction (XRD) patterns. Optical investigations were obtained with spectrometer and fluorospectrometer from Shimadzu. SEM micrographs confirm the nanostructure of the CdO film and indicate agglomeration of nanoparticles with laser irradiation. XRD patterns show decrease in the intensity of orientation peaks after laser irradiation. Variation in band gap energy, absorption peaks, and photoluminescence spectra with laser irradiation are observed.

Defects and properties of cadmium oxide based transparent conductors

Transparent conductors play an increasingly important role in a number of semiconductor technologies. This paper reports on the defects and properties of Cadmium Oxide, a transparent conducting oxide which can be potentially used for full spectrum photovoltaics. We carried out a systematic investigation on the effects of defects in CdO thin films undoped and intentionally doped with In and Ga under different deposition and annealing conditions. We found that at low growth temperatures (<200 °C), sputter deposition tends to trap both oxygen vacancies and compensating defects in the CdO film resulting in materials with high electron concentration of ∼2 × 1020/cm3 and mobility in the range of 40–100 cm2/V s. Thermal annealing experiments in different ambients revealed that the dominating defects in sputtered CdO films are oxygen vacancies. Oxygen rich CdO films grown by sputtering with increasing O2 partial pressure in the sputter gas mixture results in films with resistivity from ∼4 × 10−4 to >1 Ω cm due to incorporation of excess O in the form of O-related acceptor defects, likely to be O interstitials. Intentional doping with In and Ga donors leads to an increase of both the electron concentration and the mobility. With proper doping CdO films with electron concentration of more than 1021 cm−3 and electron mobility higher than 120 cm2/V s can be achieved. Thermal annealing of doped CdO films in N2 ambient can further improve the electrical properties by removing native acceptors and improving film crystallinity. Furthermore, the unique doping behavior and electrical properties of CdO were explored via simulations based on the amphoteric defect model. A comparison of the calculations and experimental results show that the formation energy of native donors and acceptors at the Fermi stabilization energy is ∼1 eV and that the mobility of sputtered deposited CdO is limited by a background acceptor concentration of ∼5–6 × 1020/cm3. The calculations offer an insight into understanding of the effects of defects on electrical properties of undoped and doped CdO and offer a potential to use similar methods to analyze doping and defect properties of other semiconductor materials.