Transparent Conducting Cadmium Oxide Research Articles

Characterization of jet nebulizer sprayed CdO thin films for solar cell application

The highly transparent conducting cadmium oxide (CdO) films were prepared by jet nebulizer spray pyrolysis. Characterization and optimization of CdO films have been scrutinized using various techniques such as X-ray diffraction (XRD) pattern, scanning electron microscope (SEM), energy dispersive analysis by X-ray (EDAX) spectroscopy, Atomic force microscopy (AFM), ultraviolet visible (UV-Vis) spectroscopy, hall Effect and current–voltage (I–V) characteristics. The sample prepared at 400°C with 4ml and 0.20M of volume and concentration of the precursor solution respectively have the transmittance of about 70% with a band gap of 2.37eV and the resistivity was found to be a minimum of 3.38×10−3Ωcm. The XRD, SEM and AFM studies have implied the presence of CdO nanocrystallites with cubic structure and having smooth surface. The short circuit current (Isc)=5.90mA/cm2 and open circuit volatge (Voc)=429.3mV values were established to be the maximum for the cell made with CdO films at 400°C. The fill factor (FF)=0.32 and conversion efficiency η=0.8% was also maximum for this solar cell. The low fill factor and efficiency might be due to the formation of excess silicon dioxide (SiO2) at the CdO/p-Si interface due to reaction between CdO and Si at 400°C.

Some physical properties of CdO:F thin films prepared by spray pyrolysis

Different attractions of cadmium oxide in the field of materials science especially in semiconductor science and engineering encouraged us to study its physical properties. The preparation of a transparent conducting cadmium oxide doped with various concentration of fluorine (0%, 3%, 6%) in the spray solution on a glass substrate by spray pyrolysis is reported. The structural, morphological, electrical and optical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Hall effect and UV-visible spectrophotometry. Different optical quantities such as optical band gap, refractive index, extinction coefficient, Urbach energy, oscillator energy, dispersion energy and nonlinear optical susceptibility were determined. The XRD, SEM, Hall effect and AFM showed the doping concentration effects on CdO thin-films properties. Observations such as the decrease of the sheet resistance to \( 9.20 (\Omega/\Box)\), the mobility increase up to 29.3(cm2/V·s), the transmittance up to 84% and the increase of the band gap up to 2.76(eV) state the sample CdO:F 3% is the best candidate for transparent and conducting oxide application.

Chemical spray pyrolysis deposition of transparent and conducting Fe doped CdO thin films for ethanol sensor

Transparent conducting cadmium oxide (CdO) and Fe (0.5, 1, 1.5 and 2wt%) doped CdO thin films were deposited on glass substrate using facile chemical spray pyrolysis technique. The influence of Fe doping on the structural, morphological, optical and electrical properties of CdO thin films were systematically investigated using different characterization techniques such as X-ray diffraction (XRD), atomic force microscope (AFM), UV–vis transmittance and Hall measurement respectively. The XRD patterns clearly reveal the pure and Fe doped CdO films are polycrystalline nature along with cubic crystal structure. AFM images show the roughness of the CdO thin film decreases with respect to Fe doping concentration. The surface structure of the 1wt% Fe doped CdO film was investigated by X-ray photoelectron spectroscopy (XPS). Optical transmittance of the CdO thin film decreases with increasing of Fe doping concentration. The optical band gap value of the CdO thin film gradually decreases from 2.61 to 2.18eV with increasing Fe doping concentration. From Hall measurement, the minimum value of resistivity is obtained for (7.67×10−4Ωcm) 1wt% of Fe doped CdO thin film. Finally, the ethanol sensor behaviour was observed using home-built sensor unit. The maximum ethanol gas response of 56.12% is observed for 1wt% of Fe doped CdO thin films. This result suggests the Fe doped CdO is one of the promising material in sensor applications.

Influence of growth temperature on the physico-chemical properties of sprayed cadmium oxide thin films

Transparent conducting cadmium oxide (CdO) thin films have been deposited onto the soda-lime glass (SLG) substrates using a facile and cost-effective spray pyrolysis (SPT) technique. The films have been deposited at various substrate temperatures ranging from 250 to 400°C in steps of 50°C. The influence of substrate temperature on structural, morphological and electro-optical properties of CdO thin films has been investigated. Thermo-gravimetric analysis (TGA) study indicates the formation of CdO by decomposition of cadmium acetate after 250°C. The X-ray diffraction study reveals that all samples are polycrystalline with major reflex along the (111) and (200) planes, manifested with the homogeneous distribution of roughly spherical clusters all over the substrate of varying grain size.The optical study shows band gap ranging between 2.3 and 2.5eV. The Hall effect measurement indicates that the resistivity decreases from 2.43×10−3 to 0.99×10−3Ωcm while carrier concentration increases from 2.61×1020 to 5×1020/cm3 and mobility lies in the range of 8.26–12.55cm2/Vs.

Synthesis and characterization of nanostructure CdO:Zn thin films deposited by spray pyrolysis technique: Molarity and heat treatment effects

Preparation of transparent conducting cadmium oxide doped with various concentration of Zinc (3%, 6%, 10%) in the spray solution, on glass substrate by spray pyrolysis is reported. we have tried to improve some physical properties of CdO films by Zn doping, hence the electrical, optical and structural properties of Zn doped CdO films were investigated using X-ray diffraction, Scanning electron microscopy, Hall Effect and UV–Visible spectrophotometry. Optical band gap, refractive index and extinction coefficient are also determined for different concentration. results show 6% doping is appropriate between other doping concentration, thereupon we selected this value and increased substrate temperature to acquire optimal condition. Observations like as mobility increment up to 46.9 (cm2/Vs), transmittance up to 82% and increase of band gap up to 2.62 (eV) state the sample with 400°C substrate temperature is good candidate for transparent and conducting oxide application.

Near infrared transparent conducting cadmium oxide deposited by MOCVD

Polycrystalline cadmium oxide has been deposited on to glass substrates for use as transparent conducting oxides for thin film photovoltaics. The films were deposited by metal organic chemical vapour deposition (MOCVD). The oxygen precursor was tertiary butanol, which was chosen to avoid the pre-reaction often seen for more reactive oxygen sources when combined with the cadmium source, dimethylcadmium. This combination of precursors promoted a surface reaction to yield high quality CdO films with large grain size. The cadmium oxide, deposited at 280 °C, yielded a minimum resistivity of 3.9 × 10 − 4 Ω cm whilst maintaining an average transmittance between 450 and 2500 nm of 80%. This exceptional near-IR transmittance coupled with good electrical conduction is well suited to match the infrared requirements of multi-junction photovoltaics designed to capture greater proportions of the solar spectrum.

Low resistivity transparent conducting CdO thin films deposited by DC reactive magnetron sputtering at room temperature

Transparent conducting cadmium oxide (CdO) films were deposited on PET (polyethylene terephthalate) substrate by DC reactive magnetron sputtering at room temperature. All the films deposited at room temperature were polycrystalline in rock-salt structure. Dependences of the physical properties of the CdO films on the oxygen partial pressure were systematically studied. The films deposited at low oxygen flow rate were (200) oriented, while the films deposited at an oxygen flow rate greater than 20 sccm were (111) oriented. The average grain size of the CdO films decreased as the oxygen flow rate increases as determined by XRD and SEM. The Hall effect measurement showed that CdO films have high concentration, low resistivity, and high mobility. Both the mobility and the concentration of the carrier decreased with the increase of the oxygen flow rate. A minimum sheet resistance of 36.1 Ω/□, or a lowest resistivity of 5.44 × 10 − 4 Ω cm (6.21 × 10 20/cm 3, μ = 19.2 cm 2/Vs) was obtained for films deposited at an oxygen flow rate of 10 sccm.

Optical characterisation of thin film cadmium oxide prepared by a modified reactive thermal evaporation process

The optical transmission spectra of transparent conducting cadmium oxide (CdO) thin films deposited by a modified reactive evaporation process onto glass substrates have been measured. The interference fringes were used to calculate the refractive index, thickness variation, average thickness and absorption coefficient of the films. The influence of the partial pressure of oxygen (PO2), during film deposition on the transmittance, optical constants and bandgap of the films is studied. The observation of an optimum value of PO2­ (= 0.040 Pa) at which the transmission is maximum is considered to be a particularly significant result. So, too, is the result that the width of the bandtail has a minimum at the optimum PO2 value. Key words: CdO Films, Optical Transmittance, Evaporation (Global Journal of Pure and Applied Sciences: 2003 9(4): 567-574)

Some physical properties of F-doped CdO thin films deposited by spray pyrolysis

Transparent conducting cadmium oxide (CdO) thin films have been deposited by chemical spray pyrolysis from a solution of cadmium acetate in distilled water and methanol. The films were doped by addition of NH 4F to the solution whose optimum concentration was determined. As-deposited films show values of Hall mobility , carrier concentration, resistivity, and transmittance (at λ=825 nm) of 25.4×10 −4 m 2/Vs, 3.66×10 26 m −3, 6.72×10 −6 Ω m and 87.1% respectively. The figure of merit Φ= T 10/ R sh (3.35×10 −2 Ω −1 at 825 nm) is the highest reported in the literature for doped and undoped CdO films obtained through such an inexpensive technique.

Correlations between the optical and electrical properties of CdO thin films deposited by spray pyrolysis

Transparent conducting cadmium oxide (CdO) coatings have been widely used in the fabrication of optoelectronic devices [1]. These deposits have been prepared by various techniques such as sputtering [1, 2], spray pyrolysis [2, 3], activated reactive evaporation [4] and cathodic deposition [5]. This paper is devoted to obtaining a correlation between the optical and electrical properties of undoped cadmium oxide films prepared by the spray pyrolysis technique using cadmium nitrate as the starting material.

Characterization of transparent conducting CdO films deposited by spray pyrolysis

Transparent conducting cadmium oxide (CdO) films have been deposited by spray pyrolysis. The film thicknesses have been determined using Rutherford backscattering spectrometry. X-ray diffraction measurements show that the films are polycrystalline with a preferential orientation along the (111) diffraction plane and the lattice parameter has been calculated. The dislocation density and strain have also been evaluated. The films possess a transmittance of about 75% in the visible and near-infrared region. The refractive index is found to vary between 1.68 and 2.84 in the wavelength range 500-1500 nm. The values of indirect and direct bandgaps obtained are 1.98 and 2.32 eV respectively. Hall effect measurements have been carried out in the temperature range 304-349 K. Resistivity, carrier concentration and mobility of the films at room temperature have been evaluated as 6.6*10-5 Omega m, 1.4*1025 m-3 and 0.68*10-2 m2 V-1 s-1 respectively. Thermoelectric power values from thermoelectric power measurements carried out in the temperature range 304-376 K have been found to be about 19.7-89 mu V K-1. Laser damage studies performed at a wavelength of 1.06 mu m indicate that the films possess a damage threshold density of about 2.37*104 J m-2.

Structural, optical, and electrical properties of cadmium oxide films deposited by spray pyrolysis

Transparent conducting cadmium oxide films are prepared by the spray pyrolytic technique. The dependence of structural, optical, and electrical properties on the film thickness is investigated. X-ray diffraction studies confirm the polycrystallinity of the films and the films show preferential orientation along the (200) plane. The crystallite size and the dislocation density are also determined from the above patterns. The films show about 70% transmittance in the wavelength range 750 to 850 nm and the values of band gap and refractive index are in the order 2.35 to 2.50 eV and 1.95 to 2.65, respectively. Hall measurements indicate that the films are n-type, having carrier concentration ≈ 1026 m−3 and mobility (17.5 to 19) × 10−4m2/Vs.

Transparent conducting cadmium oxide thin films prepared by a solution growth technique

Thin films of cadmium oxide have been deposited on glass substrates from a chemical bath containing cadmium ammine complex ions. They have fairly good adherence to glass and their thickness varied between 0.2 and 0.6 μm. Optical absorbance, transmittance and reflectance data of the films have been used to obtain the dispersion relation of their optical constants. The films are n-type semiconducting with an optical bandgap of 2.3 eV. They have transmittance of over 85% in the spectral range 530–900 nm. The films have room temperature resistivity of (2−5) × 10t-4 Ωm.