Doped CdO Research Articles

Polariton design and modulation via van der Waals/doped semiconductor heterostructures

Hyperbolic phonon polaritons (HPhPs) can be supported in materials where the real parts of their permittivities along different directions are opposite in sign. HPhPs offer confinements of long-wavelength light to deeply subdiffractional scales, while the evanescent field allows for interactions with substrates, enabling the tuning of HPhPs by altering the underlying materials. Yet, conventionally used noble metal and dielectric substrates restrict the tunability of this approach. To overcome this challenge, here we show that doped semiconductor substrates, e.g., InAs and CdO, enable a significant tuning effect and dynamic modulations. We elucidated HPhP tuning with the InAs plasma frequency in the near-field, with a maximum difference of 8.3 times. Moreover, the system can be dynamically modulated by photo-injecting carriers into the InAs substrate, leading to a wavevector change of ~20%. Overall, the demonstrated hBN/doped semiconductor platform offers significant improvements towards manipulating HPhPs, and potential for engineered and modulated polaritonic systems.

Investigations of Structural, Morphological, Optical and Antimicrobial Behaviour of Bi Doped CdO Nanostructures

Investigations of Structural, Morphological, Optical and Antimicrobial Behaviour of Bi Doped CdO Nanostructures

Study of induced half-metallic ferromagnetic property in CdO monolayer with non-metallic doping

Doping is known to be an efficient way of altering the properties of materials. We have studied the structural, electronic and magnetic properties of non-metallic element (B, C and N)-doped CdO monolayer based on spin-polarized density function theory within the generalized gradient approximation (GGA) as revised for solids by Perdew, Burke and Ernzerhof (PBE-sol). Substituting B, C and N in O site with one atom in CdO monolayer induces spin polarized localized states in the gap or near the valence band and exhibit local magnetic moments ~ 1 μΒ, ~ 2 μΒ and ~ 1 μΒ respectively. It is found that the magnetic states in these doped systems are associated with the difference between the electronegativity of the dopant and the anion in the host. Our study shows that non-metal doped CdO is a promising candidate for novel nano-materials for future applications.

The spectral responsivity enhancement for gallium-doped CdO/PS heterojunction for UV detector

Despite the large number of studies on CdO, it was until very recently the system properties Ga-doped CdO/PS was not recognize well. In this paper, photodetector of Gadoped CdO/Si and Ga-doped CdO/PS nanocrystalline with different Ga ratios (0, 3, and 7%) have been prepare by spray pyrolysis deposition (SPD). The structural properties of un doped CdO and doped films were characterized by X-ray diffraction, which refer to that the CdO thin films have cubic structure. The energy gap of un doped film and doped with Ga increased from 2.5 to 3.56 eV with increasing Ga ratios. I-V characteristics of Gadoped CdO/PS photodiodes without illumination exhibit good rectification behavior compared with Si substrate, and the value of photocurrent increased with Ga ratios increased. The spectral responsivity curves (A/W) of all devices prepared allow acceptable sensitivity response in the visible wavelength region, and shifted toward ultra-violet region with increase Ga ratios.

Electrical resistivity and magnetic susceptibility of substoichiometric CdO and In doped CdO films

Undoped and In doped substoichiometric CdO nanostructured films were prepared via vapor transport method. Mixed phases of hexagonal Cd and cubic CdO were obtained. No peaks related to In or indium oxides were observed in the In doped CdO pattern. Net-like assembles of nanowires were observed for undoped CdO sample whereas a regular morphology of equally shaped grains was observed for In doped CdO sample. The evaluated room temperature electrical resistivity values for undoped and In doped CdO films were 1.56 × 102 and 2.31 × 10–2 Ωcm, respectively. The temperature dependent resistivity measurements elucidated the semiconducting behavior for undoped CdO films, whereas a semiconductor–metal with a transition around 367 K was obtained for In doped CdO film. The magnetic susceptibility showed paramagnetic-antiferromagnetic transition with Neel temperatures of 266 and 308 for undoped and In doped CdO samples, respectively.

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.

Photocatalytic Degradation of Azo Dyes by Pure and Aluminium Doped CdO Nanocrystalline Thin Films

Photocatalytic Degradation of Azo Dyes by Pure and Aluminium Doped CdO Nanocrystalline Thin Films

Structural, electrical and optical characterization of Mn doped CdO photodiodes

Undoped CdO, 0.2% Mn doped CdO, 6% Mn doped CdO and 10% Mn doped CdO photodiodes were prepared using sol-gel method and deposited on Si substrate at room temperature. Electrical and optical properties of the diodes were assessed, and surface properties were investigated using atomic force microscopy. Atomic force microscopy assessment revealed that undoped and Mn doped CdO thin films were formed in a granular structure where grains composing thin film spread homogeneously on a substrate. To assess the electrical properties current - voltage (I - V), current – time (I - t) graphs were obtained in various illumination intensities; it was seen that diodes show rectifying properties and good photovoltaic behaviour. Photo-characterizations revealed that photodiodes show increasing photocurrent with increasing illumination intensities; the photodiodes also show decreasing capacitance with increasing frequency. Optical properties of the thin films were assessed using UV–vis spectrometry. Bandgap energies were calculated using UV–vis absorption spectra which were found between 2.41 eV and 1.70 eV.

Antibacterial Application of Undoped and Doped CdO Nanocrystalline Thin Films

Antibacterial Application of Undoped and Doped CdO Nanocrystalline Thin Films

A Comprehensive Review of Properties of Screen-Printed Pure and Doped ZnO and CdO Thick Films

A Comprehensive Review of Properties of Screen-Printed Pure and Doped ZnO and CdO Thick Films

Analysis of Sn Concentration Effect on Morphological, Optical, Electrical and Photonic Properties of Spray-Coated Sn-Doped CdO Thin Films

Tin-doped cadmium oxide (Sn:CdO) transparent thin films with different Sn concentrations were deposited on glass and p-silicon substrates by the chemical spray method at 250 °C. Different concentrations of stannic chloride were used to prepare Sn:CdO thin films. The prepared doped and un-doped CdO films were subjected to X-ray diffraction (XRD), scanning electron microscopy and atomic force microscopy, optical absorption, and electrical analyses to characterize their structural, morphological, optical, and electrical properties, respectively. XRD analysis demonstrated the growth of polycrystalline and cubic CdO with preferential orientation along the (111) plane. Sn-doping shifted the XRD peaks slightly towards a higher Bragg angle and increased the band gap of CdO thin films. Variation in doping concentration also affected the morphology of the films. Optimum Sn-doping increased the electrical conductivity of CdO thin films. Furthermore, to the best of our knowledge, the photoresponse analyses of the fabricated un-doped and doped n-CdO/p-Si heterostructures were performed for the first time in this study.

Sol–Gel Synthesis of Aluminum Doped CdO Thin Films for Optoelectronic Applications

Sol–Gel Synthesis of Aluminum Doped CdO Thin Films for Optoelectronic Applications

Zn doped CdO nanoparticles: Structural, morphological, optical, photocatalytic and anti-bacterial properties

Pure and zinc-doped CdO NPs (Zn-CdO NPs) were synthesized through a facile co-precipitation method. The structural, morphology, chemical composition, optical and antibacterial activity of the NPs were studied with respect to pure and Zn-doped CdO concentration (0–7.5mol.%). Scanning electron microscope (SEM) images reveal that pure and Zn-doped CdO NPs were in the nano-scale regime with different crystalline morphology. The energy dispersive X-ray spectroscopy (EDS) spectrum predicts the presence of Cadmium (Cd), Zinc (Zn) and Oxygen (O) in the prepared samples. Optical studies divulge that Zn2+ doping CdO decreases the band gap energy (Eg) (3.36–3.02eV) with an increase in Zn2+ doping concentration. Optical absorption spectrum of CdO red-shifted as the Zn concentration varied from 2.5mol.% to 7.5mol.%. PL spectra displayed a strong UV emission peak at 380nm. Enhanced Visible emission at 430 and 522nm with Zn2+ doping interprets the defect density in CdO by occupying Cd2+ vacancies with Zn2+ ions. Photocatalytic studies revealed that 7.5% Zn-doped CdO NPs show maximum degradation for atrazine (ATZ) as herbicide pollution under UV irradiation. Antibacterial studies against (Gram positive) and (Gram negative) bacteria's authenticate that Zn2+ doped CdO nanostructures exhibit excellent antibacterial activity against all bacteria's with an increase in doping concentration.

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.

Shape Controlled Plasmonic Sn Doped CdO Colloidal Nanocrystals: A Synthetic Route to Maximize the Figure of Merit of Transparent Conducting Oxide.

The synthesis of different anisotropic shaped (eight different shapes) Sn4+ doped CdO (Sn:CdO) colloidal nanocrystals (NCs) by precise tuning of precursor reactivity and proper choice of capping agent is reported. In all these systems, formation of Sn:CdO quantum dots (QDs) of 2-3 nm is identified at very early stage of reaction. The colloidally stable QDs act as a continuous source for the formation of primary nanoparticles that can be transformed selectively into specific type of nanoparticle morphology. The specific facet stabilization of fcc (face centered cubic)CdO is predicted by particular choice of ligand. Fine tuning of plasmonic absorbance band can be achieved by variation of Sn4+ doping concentration. Different anisotropic Sn:CdO NCs exhibit interesting shape dependent plasmonic absorbance features in NIR region. High quality crack free uniform dense thin film has been deposited on glass substrate to make high quality transparent conducting oxide (TCO) coatings. figure of merit of TCO can be maximized as high as 0.523 Ω-1 with conductivity of 43 600 S cm-1 and visible transmittance of ≈85% which is much higher than commercially available tin doped indium oxide and other transparent electrodes.

Effect of Laser Exposure on Structural and Optical Properties of CdO and Li Doped CdO Nano Structured Thin Film Synthesized by Sol Gel Method

Effect of Laser Exposure on Structural and Optical Properties of CdO and Li Doped CdO Nano Structured Thin Film Synthesized by Sol Gel Method

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.

Indium doped Cd1-xZnxO alloys as wide window transparent conductors

We have synthesized Indium doped Cd1-xZnxO alloys across the full composition range using magnetron sputtering method. The crystallographic structure of these alloys changes from rocksalt (RS) to wurtzite (WZ) when the Zn content is higher than 30%. The rocksalt phase alloys in the composition range 0<x<0.3 can be efficiently n-type doped, shifting the absorption edge to 3.25eV and reducing resistivity to about 2.0×10−4Ω-cm. We found that In doped CdO (ICO) transmits more solar photons than commercial fluorine doped tin oxide (FTO) with comparable sheet conductivity. The infrared transmittance is further extended to longer than 1500nm wavelengths by depositing the In doped Cd1-xZnxO in ~1% of O2. This material has a potential for applications as a transparent conductor for silicon and multi-junction solar cells.

Structural and Spectral Characterization of Co2+- and Ni2+-DOPED CdO Powder Prepared From Solution at Room Temperature

The mild and simple solution method was used for the synthesis of Co2+- and Ni2+-doped CdO powders at room temperature. The prepared powders were characterized using powder X-ray diffraction, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), optical absorption, and Fourier transform infrared spectroscopy (FTIR). From the powder X-ray diffraction patterns, it has been observed that the prepared Co2+ and Ni2+ ion-doped CdO powders belong to the cubic phase, and the evaluated average crystalline sizes of the powders are 20 and 14 nm, respectively. The SEM images and the EDS spectra show that the prepared powders are distributed over different sizes in the grain boundaries. Optical absorption studies allow determination of site symmetry of the metal ion with its ligands. The crystal field (Dq) and inter-electronic repulsion (B and C) parameters have been evaluated from the optical absorption spectra. The FTIR spectra show the characteristic fundamental vibrations of the metal oxide and CdO.

Effect of Annealing Temperature on Physical Properties of Indium Doped Cadmium Oxide Thin Films

Nanostructured indium doped CdO thin films were prepared by spray pyrolysis on glass substrate and annealed at 200-400 ᵒC for 1 hour. The structural, optical, and electrical properties of prepared films were studied using different techniques such as optical transmission, photoluminescence, X-ray diffraction, and Hall measurement. X-ray analysis shows that the In doped CdO films are preferentially orientated along (111) crystallographic directions. Increasing of annealing temperature increases the films packing density and reorient the crystallites along (1 1 1) plane. The optical transmissions of all annealed films decreased with increasing annealing temperature. An increasing in the absorbance and photoluminescence spectra with increasing annealing temperature was denoted in all films. The band gap value of CdO:4%In equals to 2.5 eV and it decreases with annealing temperature and reaches of 2.45 eV for 400°C. The resistivity of annealed films decreased as annealing temperature increased. While high conductivity achieved in the present study is found to be 11.37 ×102 (Ω.cm)-1 for annealing at 400°C.