CdO Films Research Articles

Correction to: An Investigation of Spray Deposited CdO Films and CdO/p-Si Heterojunction at Different Substrate Temperatures

This article was corrected to remove extraneous units of eV for ideality factor introduced during the production process.

Enhancing the properties of CdO thin films by co-doping with Mn and Fe for photodetector applications

In this communication, we report on how the co-doping of two transition metal ions (Fe and Mn) effectively improves the structural, morphological, optical, electrical and photodetection properties of CdO thin films than individual doping. For this, pure-CdO, Fe-doped, Mn-doped and (Fe-Mn) co-doped CdO thin films are deposited by spray pyrolysis technique. X-ray diffraction (XRD) patterns reveal that these films possess cubic structure and belong to the Fm-3 m space group. The Field Emission Scanning Electron micrographs hold a qualitative agreement with the crystalline sizes obtained from the XRD analysis. Energy Dispersive X-Ray Analysis approved the existence of constituent elements in the prepared films. The photoluminescence spectra identified the quality of crystal structure and the presence of defects in the prepared films. Analyzing the absorption spectra unveiled the direct bandgap values in the range 2.32 eV (for pure-CdO) - 1.96 eV (for CdO:Fe(1%):Mn(1%)). The Hall Effect measurements established n-type behavior with the values of resistivity (ρ), carrier concentration (n) and carrier mobility values in the range 5.8–7.1 mΩcm, 6.7−2.4 × 1019 cm−3 and 16−37 cm2/Vs, respectively. Three different transport mechanisms such as ohmic, recombination-tunneling and space-charge limited current are found to play roles in the three distinct ranges of the I–V data measured for the films under study. The ideality factor values are obtained from the region where the recombination-tunneling mechanism is prevalent. The photoelectric parameters such as photo-responsivity, and external quantum efficiency are obtained. The values of these quantities pertaining to pure-CdO, CdO:Mn, CdO:Fe and CdO:Fe:Mn films vary in the range 128.4–561.3 mA/W, and 30–131.1 %, respectively. From the current study, it was found that photoresponsivity and external quantum efficiency are enhanced by a factor of four in codoped CdO films than the undoped CdO film and can find potential photodetector applications.

Structural, morphological, optical and enhanced photodetection activities of CdO films: An effect of Mn doping

In this work, undoped and Mn of various concentration (1, 3 and 5 %) doped CdO films prepared by spray pyrolysis procedure using perfume atomizer is reported. XRD analysis of the samples approves polycrystalline nature with cubic system. Change in crystallite size, lattice constant, and cell volume are observed due to the imperfection of crystal lattice. Tightly packed uniformed spherical shape particles are visualised from the morphology anaysis. In PL studies, the emission peaks are observed at 360, 490, 520, and 590 nm. From the UV–vis, the absorbance is increased with doping concentration, which may be due to electronic transition from V to C-band. The bandgap values are decreased with increasing doping concentration (2.51, 2.47 and 2.21 eV) and furher increased for higher doping concentration (2.37 eV). The high resistivity obtained for 3% Mn doped film may be the vital to decrease the dark current and increase the photodetector properties. I–V characteristics of the devices showed increased photosensitivity, responsivity, and quantum efficiency for 3 % of Mn doped film due to high crystallinity, low bandgap, and maximum energy transfer of Mn ions.

An Investigation of Spray Deposited CdO Films and CdO/p-Si Heterojunction at Different Substrate Temperatures

In this study, CdO films were successfully obtained by using a homemade chemical spray pyrolysis technique. The crystal structures of the CdO thin films improved due to an increase in the substrate temperature when the spray time was kept constant. Additionally, CdO film deposited at 250°C exhibited amorphous crystal structure. The surface morphology of the samples was evaluated by scanning electron microscope (SEM) and it was observed that well-defined granules started to be clearly seen when the substrate temperature increased. Optical properties of CdO films were also investigated by using an ultraviolet–visible (UV–Vis) spectrophotometer, and the optical band gap of CdO varied from 2.57 eV to 2.73 eV with increasing substrate temperature. The electrical performance of the CdO films in the Au/CdO/p-Si device were determined by I–V measurements. According to the results, it was found that diode parameters depend on the changing properties of CdO in terms of the substrate temperature.

The effect of tin doping level on the physical properties and photocatalytic degradation of cadmium oxide nanostructured film

Pure and tin (Sn) doped CdO films were deposited onto soda-lime glass via ultrasonic spray pyrolysis (USP) method with Sn concentrations of 1, 2 and 3%. The effect of doping level on the structural, morphological and optical properties of the films was explored by using several diagnostic techniques including X-ray diffraction, atomic force microscopy, UV–Vis spectroscopy and Hall effect methods. The doping level in the CdO film affects the photocatalytic performance of the nanostructured films. It has been declared that the physical properties of the highly conducting and transparent nanostructured CdO films can be modified/controlled by tin doping for optoelectronic applications.

The consequence of gadolinium doping on optical and electrical characteristics of CdO film developed by the sol–gel derived screen printing process

A sol–gel derived screen printing process was employed to develop a 3% (Gd)-doped CdO film on the glass substrate. X-ray diffraction (XRD) pattern endorses that 3% (Gd)-doped CdO film possess cubic structure and polycrystalline nature. The high-intensity peak was observed along (2 0 0) direction and the mean crystallite size were found to be 22.2 nm. SEM (Scanning electron microscope) image shows uniform arrangements of spherical and circular grains in the film. The composition of the gadolinium in developed film was confirmed by EDAX spectra. The UV–Visible spectroscopy shows the transmittance up to 58% and the optical band gap (Eg) value of 2.61 eV for a 3% (Gd)-doped CdO film. The n-type conductivity of film was confirmed by Hall-effect measurement. The electrical resistivity (ρ) and carrier concentration (n) of 3% (Gd)-doped CdO film was found to be (∼3.54 × 10−4 Ω cm) and (∼10.0 × 1020 cm−3).

Study the Structural Properties and Surface Morphology of CdO thin films prepared by Chemical Spray pyrolysis

CdO films were prepared using a chemical spray paralysis (CSP) method on the glass substrate at a temperature of 350 ° C and thickness (260 ± 15 nm), and study the effect time of annealing (0, 1, 1.5, 2, 2.5) h at a 450 °C annealing temperature On structural properties.from X-ray diffraction pattern the results showed that all CdO thin films have a polycrystalline crystalline structure and a prevalent growth in the direction (111), and the average grain size (G) in this direction ranges (29.80 - 33.23) nm. It generally increases in value while the agitation values, extraction density, number of crystals decrease by increasing the time of annealing (1-2) h of thin films.And from resulted of Atomic Force Microscope (AFM) the surface roughness , root mean square ( RMS ) and average grain size increase with increasing of annealing time, Expect for melting thin films at temperatures 450 ̊C and for the time of annealing 2.5h note decrease slightly may be the possibility of an occurrence the cracks- free of the thin films component.

CdO/FTO Schottky photodetector with enhanced spectral responsivity and Specific detectivity prepared by electrolysis method

One of the important materials for applications in many photoelectric filed [just like solar cell, optoelectronic and other kinds on devices] is cadmium oxide thin films. There are several physical or chemical synthetic methods have been used to prepare transparent CdO films as described by many researchers. The X-ray diffraction study has confirmed the formation of CdO with nano-size scale. For this research CdO/FTO thin film has been prepared by electrolysis. The thin film is investigated by XRD, SEM and AFM surface morphology properties. XRD analysis showed that CdO films are a polycrystalline and exhibit cubic crystal structure with (111, 200, 311 and 222) orientation and the preferred orientation is 111. AFM and SEM were applied to study the morphology and estimate the surface roughness of the films obtained. (RMS) found that film roughness was 21.7 nm. The CdO film are n-type semiconductors and possess a direct optical band gap around 2.4 eV as shown in optical property studies.

Effect of annealing temperature on structure and optical properties of CdO nanocrystaline thin film prepare by chemical bath deposition method

CdO thin film has been deposited by chemical bath deposition method (CBD) on the glass substrate. Effect of annealing temperature( 573,623 and 673 K) on the structural and optical properties of the films has been investigated. The crystal structure investigated by X-ray diffraction method. Annealed CdO films are polycrystalline in nature with cubic structure having a preferential orientation along (1 1 1) plane. Analysis of XRD indicates that the intensities of peaks of the crystalline phase have increased with the increasing of annealing temperature. The structural parameters for the CdO thin films as the grain size, strain, dislocation density, and texture coefficient were calculated. Particle size for the preferential orientation at different annealing temperature is (16.95, 18.24 nm) for annealing temperature 623 and 673 K respectively. Optical properties study of CdO thin films using UV-vis spectrophotometer shows blue shift in the energy band gap as an indication of quantum confinement. It is observed that the band gap energy decreases with increasing of annealing temperature. The direct and indirect band gap energy values were found to be (2.95 2.87) and (1.945,1.914) eV respectively.

Structural investigation and optical enhancement characterization of nanostructured Ga-doped @CdO/FTO films for photodiode applications

Abstract In this work, the high quality of CdO film with a different percentage of Ga doping prepared onto optically flat glass substrates using a sol-gel spin coating progression for enhancement of its structural characteristics for various applications. X-ray diffraction results confirm that the prepared films of CdO are amorphous due to the long-range array of deposited crystals. The images of the atomic force microscopy indicated that the surface morphology of the pure and Ga-doped CdO films has high roughness values of 60–80 nm and average particle size 85–100 nm. The optical constants were calculated using the Kramer-Kronig approach. The calculated optical transmission specifies a high transmission exceeding from 77% to 85% through the non-absorbing region depending on the doping concentrations. The results confirm that the measured optical band gap is strongly influenced by doping concentrations of Ga and decreases from 2.35 to 1.72 eV. The calculated optical dispersion and non-linear optical parameters were found to be strongly affected by doping. The terahertz cut-off frequency was set for the pure and Ga-doped CdO films indicating the applicability of the prepared films as terahertz filters.

Effects of Electrolyte on CdO Films Obtained by Electrodeposition

Electrodeposition method was used for synthesis of CdO thin films. In the experiments, 0.02 M CdCl2 and 0.02 M Cd(NO3)2were used as to be an electrolyte in various volumes. As concentration of Cd(NO3)2increased, film thicknesses and crystallite sizes decreased. Remarkable results were observed in the optical properties of the CdO thin films. As the volume of used Cd(NO3)2increased, the band gap also increased from the 2.30 eV to the 2.63 proportionally. For the first time in the SEM image, the pyramidal form of CdO was observed.

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.

Influence of incorporation of carbon on the transparent conducting properties of CdO thin films

Thin films of CdO incorporated with different amounts of carbon element have been deposited on glass substrates by using the vacuum thermal evaporation method aiming at improving their transparent conducting (TC) properties. The structural and opto-electrical properties of the host CdO films were systematically studied. X-ray diffraction and optical investigations confirmed the inclusion of C species in the CdO lattice. The obtained results were explained through the occupation of interstitial positions and structural vacancies of the host CdO lattice by C species. It was observed that the inclusion of carbon into the CdO lattice blue-shifted the optical band gap by $${\sim }5{-}7$$ %, which was attributed to the Moss–Burstein (B–M) effect. The electrical studies showed that the carrier mobility increased steadily with the increase in the C% inclusion level, so that with 5 wt% it attained $${\sim }7.5$$ times the carrier mobility in un-doped CdO. Therefore, the present study showed that the prepared host CdO–C films have controllable TC degenerate semiconducting properties, which could be required in different optoelectronic applications.

ELABORATION AND CHARACTERIZATION OF NANOCRYSTALLINE CADMIUM OXIDE FILMS

Cadmium oxide in thin film was deposited on glass substrates by spray pyrolysis technique from aqueous solution of cadmium nitrate. The diagrams of X-ray diffraction show that the films are polycrystalline. Morphological study shows uniform deposited film and submicron sized grains growth perpendicularly on substrate surface. Optical gap energy of cadmium oxide was estimated to be 2.15eV. Optical study shows that CdO film transmitted in visible and in the near red infrared wavelength range. The conductivity study indicates a semi-conducting behavior of cadmium oxide in thin films. Dielectric response of cadmium oxide films was interpreted by orientation and space charge polarization.

Influence of Sn doping ratio on the structural and optical properties of CdO films prepared by laser induced plasma

In this work, we study the effect of doping Sn on the structural and optical properties of pure cadmium oxide films at different concentrations of Tin (Sn) (X=0.1,0.3 and 0.5) .The films prepared by using the laser-induced plasma at wavelength of laser 1064 nm and duration 9 ns under pressure reached to 2.5×10-2 mbar. The results of X-ray diffraction tests showed that the all prepared films are polycrystalline. As for the topography of the films surface, it was measured using AFM , where the results showed that the grain size increases with an increase in the percentage of doping in addition to an increase in the average roughness. The optical properties of all films have also been studied through the absorbance spectrum of the range of the wavelength (350-1100) nm, where the optical energy gap was direct transitions it was found that the value of the optical energy gap increased with increasing the doping.

Comparison of the structure, electronic, and optical behaviors of tin-doped CdO alloys and thin films

Spray pyrolysis technique (SPT) was applied to fabricate CdO films doped with tin at (0–8%) concentrations on glass substrates. Structural, morphological, and optical behaviors were inspected using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–Vis spectroscopy. Structural, electronic, and optical behaviors of Cd1−xOSnx alloys were studied in pseudo-potential method using density functional theory (DFT) in scissors approximation. The calculated electronic band structure and optical behavior were achieved in this work. Optical bandgap energy was found to increase from 2.581 to 2.943 eV via increasing Sn content, while theoretically, it was found to increase from 2.884 to 3.106 eV with the increasing Sn doping. Theoretical and experimental findings were close to each other. The linear energy-dependent dielectric functions (real part) and optical behavior-like absorbance and transmittance were also studied.

Effect of Mg Molar Concentration on Structural and Optical Properties of CdO Thin Films Prepared by Chemical Bath Deposition Method

In this study, pure and Mg doped CdO thin films were coated on glass substrate using a chemical bath deposition method. Adding different molar concentrations of magnesium (0, 2, 4, 6) % to the chemical bath solution and their effect on the structural and optical properties were studied. Oxidation of films was conducted at 573 K for 60 minutes in the presence of static air. The thin film properties were diagnosed with X-ray diffraction techniques and UV-VIS-spectrophotometer. The results of X-ray diffraction for the thin films showed that all prepared thin films have a faced-centered cubic crystal structure (FCC) with a preference for growth at level (111), and the synthetic coefficients calculated from the X-ray spectrum are affected with increasing Mg ratios in the chemical bath solution. The results of the optical tests showed that the absorption of the resulting thin films increases with increasing Mg ratios in the chemical bath solution, have a high absorption coefficient in the visible region of the electromagnetic spectrum, and the transmittance decreases with the increase of Mg in the chemical bath solution. The optical energy gap of the prepared thin films changes with increasing Mg doping rates and extends from (2.46) eV to (2.95) eV. The results showed a significant improvement in the structural and optical properties of Mg ion doped CdO films making it suitable for use in many photovoltaic applications such as reagents and solar cells.

Effect of Doping on the Morphological, Micro-Structural and Optical Properties of Cd1–(x + y)MnxFeyO Thin Films

Transition metal doped cadmium oxide (Cd1–(x + y)MnxFeyO) thin films with high purity were prepared using the spray pyrolysis method. The morphological analyses were done using scanning electron microscope and atomic force microscope. The X-ray diffraction studies indicated that the structure of cadmium oxide lattice remains same even after mono-doping (Cd1–xMnxO and Cd 1–yFeyO) and co-doping (Cd1–(x + y)MnxFeyO). The micro-structural properties such as crystallite size, dislocation density, strain and texture coefficient depends on the nature of doping. The Mn and Fe co-doped CdO films (Cd1–(x + y)MnxFeyO) have low transmittance, low band gap, high n-type charge carrier concentration and high refractive index than mono-doped CdO films. The intensity of luminescence also depends on the nature of doping.

Ultraviolet to far-infrared dielectric function of n -doped cadmium oxide thin films

Spectroscopic ellipsometry and Fourier transform infrared spectroscopy were applied to extract the ultraviolet to far-infrared $(150--33333\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1})$ complex dielectric functions of high-quality, sputtered indium-doped cadmium oxide (In:CdO) thin crystalline films on MgO substrates possessing carrier densities $({N}_{d})$ ranging from $1.1\ifmmode\times\else\texttimes\fi{}{10}^{19}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}3}$ to $4.1\ifmmode\times\else\texttimes\fi{}{10}^{20}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}3}$. A multiple oscillator fit model was used to identify and analyze the three major contributors to the dielectric function and their dependence on doping density: interband transitions in the visible, free-carrier excitations (Drude response) in the near- to far-infrared, and IR-active optic phonons in the far-infrared. More specifically, values pertinent to the complex dielectric function such as the optical band gap $({E}_{g})$, are shown here to be dependent upon carrier density, increasing from approximately 2.5--3 eV, while the high-frequency permittivity (${\ensuremath{\varepsilon}}_{\ensuremath{\infty}}$) decreases from 5.6 to 5.1 with increasing carrier density. The plasma frequency (${\ensuremath{\omega}}_{p}$) scales as $\sqrt{{N}_{d}}$, resulting in ${\ensuremath{\omega}}_{p}$ values occurring within the mid- to near-IR, and the effective mass (${m}^{*}$) was also observed to exhibit doping density-dependent changes, reaching a minimum of $0.11{m}_{o}$ in unintentionally doped films ($1.1\ifmmode\times\else\texttimes\fi{}{10}^{19}\phantom{\rule{4pt}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}3}$). Good quantitative agreement with prior work on polycrystalline, higher-doped CdO films is also demonstrated, illustrating the generality of the results. The analysis presented here will aid in predictive calculations for CdO-based next-generation nanophotonic and optoelectronic devices, while also providing an underlying physical description of the key properties dictating the dielectric response in this atypical semiconductor system.

Optical and electrical properties of organic dye sensitized Cr–ZnO and Ni–CdO nanoparticles

In this work presents an approach for the selection of dye sensitized Cr–ZnO and Ni–CdO nanoparticles as a photo anode material for the applications of DSSCs. The 4 wt% Cr–ZnO and Ni–CdO nanoparticles were synthesized through simple and fast microwave combustion method. X-ray difraction (XRD) was used for the detection of crystalline phases and size of the synthesized nanomaterials. It confirms the existence of hexagonal wurtzite phase of Cr–ZnO (30–35 nm) and cubic phase of Ni–CdO (43–45 nm) nanoparticles. SEM and TEM micrographs of Cr–ZnO and Ni–CdO reveal that the synthesized samples are prismatic and spherical shaped, respectively. Optical absorption of Cr–ZnO and Ni–CdO nanoparticles before and after sensitization with Trypan Blue (TB), SPADNS (SPD) and Evans Blue (EB) dyes were examined through UV–Visible spectroscopy. The results show that the selected dyes improve the absorption edge of Cr–ZnO and Ni–CdO nanoparticles to longer wavelength side. HOMO and LUMO energy levels of the dyes were calculated by cyclic voltammetry. I–V characteristics of Cr–ZnO and Ni–CdO films before and after sensitization with dyes revealed the influence of dye sensitization on photo conductivity of Cr–ZnO and Ni–CdO nanoparticles.