Optical Properties Of CdTe Research Articles

Combined X-ray Diffraction Analysis and Quantum Chemical Interpretation of the Effect of Thermal Neutrons on the Geometry and Electronic Properties of CdTe

Objective: Substantiation of the result of the interaction of thermal neutrons with CdTe crystals by quantum-chemical methods and comparison of the experimental results with the results of quantum-chemical calculations. Methods: Single crystal samples of cadmium telluride (CdTe) were obtained by a modified Bridgman method. The plates cut from the single crystal were subjected to mechanical grinding with abrasive paper of the type P1,200-P4,000, mechanical polishing with silver paste. To clean the surface of the plate from contamination, it was washed in ethyl alcohol. In the experimental part of the work, the influence of low thermal neutron fluxes on the structural parameters of CdTe was studied. The samples were irradiated with a thermal neutron flux in the range from 2.64×107 neutron/cm2 to 1.85×109 neutron/cm2. To study the structure of CdTe crystals, the method of X-ray structural analysis was used, using a DRON-3 X-ray diffractometer. In the second part of the work, computer modeling of the process of interaction of thermal neutrons on CdTe crystals was carried out. Results: X-ray diffraction analysis of the crystals showed that as a result of irradiation with low thermal neutron fluxes, the structural parameters of CdTe improve, as evidenced by the ordering of the crystallites. In addition, in this region of the thermal neutron flux the resistance of the crystals decreases. Conclusion: Calculations of the crystal lattice parameters of CdTe are in good agreement with experimental data. The electronic and optical properties of CdTe have been studied. A decrease in the band gap after irradiation with thermal neutrons has been shown.

Antibacterial potential and dye decolorization with graphitic carbon nitride and eudragit doped CdTe nanostructures evidential molecular docking analysis

Co-precipitation procedure was employed to prepare efficient ternary system-based catalysts composed of various concentrations (2 and 4 wt.%) of graphitic carbon nitride (g-C3N4) and fixed amount (3 wt.%) of eudragit (Eud)-doped cadmium telluride (CdTe) nanostructures (NSs). The main objective of this study was to explore and enhance the dye degradation potential by changing the recombination rate of CdTe with doping and improving their multifunctional efficacy as catalysts and antibacterial agents. The dopants have altered the particle size, dispersal and optical properties of CdTe. The different concentrations of g-C3N4 and fixed amount of Eud, reaction temperature, and duration influence these characteristic properties of CdTe. g-C3N4 /Eud-doped CdTe with porous structure showed excellent methyl orange (MO) dye degradation efficiency (98.0 %) in neutral medium. Furthermore, 4 wt.% of g-C3N4 doped NSs exhibited significant inhibition zone as 9.35 ± 0.08 mm against MDR S. aureus bacteria. The molecular docking studies were conducted to elucidate the mechanistic interactions between g-C3N4/Eud-doped CdTe nanostructures and the target enzymes DNA gyrase S. aureus and D alanine-D-alanine ligase (ddlB)S. aureus, in order to justify their microbicidal efficacy.

Solar cells based on CdTe thin films (Part II)

This paper discusses the use of semiconductor solar cells based on thin-film cadmium telluride (CdTe) in modern energy production. The advantages and disadvantages of using CdTe thin-film solar cells are analyzed, and arguments are presented in favor of the implementation of mass production technologies for CdTe solar modules, which can compete with silicon analogs in terms of compromise between efficiency and cost. The physical and chemical properties of the binary Cd-Te system are described, and the relationship between the physical, chemical, electrical, and optical properties of CdTe is analyzed, making it attractive for use in thin-film solar cells. Special attention is given to the investigation of photovoltaic properties, which are important parameters for determining photoconductivity, and the advantages and disadvantages of CdTe film photovoltaic properties are discussed. CdTe thin-film heterostructures (HSs), which are important components of modern solar cells, are considered, and their main advantages and disadvantages are described. It is argued that simple methods of manufacturing and forming HSs, which do not require complex and expensive equipment, are an important advantage of CdTe-based solar cell technology.

Optical Properties of CdTe:In Thin Films Deposited by PVD Technique

Optical Properties of CdTe:In Thin Films Deposited by PVD Technique

Structural and optical properties of CdTe + CdTeO3 nanocomposite films with broad blueish photoluminescence

Cadmium telluride plus cadmium tellurite (CdTe + CdTeO3) nanocomposite films were grown by radio frequency magnetron sputtering at room temperature. The CdTe + CdTeO3 samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, UV–Vis absorption, and room temperature photoluminescence (RTPL). XRD and TEM results indicate that films are composed of CdTe and CdTeO3 nanoparticles (NP’s) with 6.7 ± 0.8 nm and 6 ± 1 nm in size, respectively. CdTe NPs grew in hexagonal wurtzite and cubic zinc blende crystalline phases. CdTeO3 NPs are crystalized in cubic phase. Direct bandgap (Eg) (first discrete electronic transition) calculation indicates Eg = 2.6 ± 0.2 eV for CdTe and 3.3 ± 0.2 eV for CdTeO3. RTPL spectrum evidences a wide signal in the 2.0 to 3.25 eV interval. Results reveal that the emission band maximum, which is centered in the blue region of the visible light, is related with band-to-band transitions in CdTe NPs.

Structural and Optical properties of CdTe:CuThin Films by Pulsed Laser Deposition technique

Polycrystalline cadimumtelluride : copper composite thin films were deposited on a glass substrate by pulsed laser deposition technique(PLD).Using Nd:YAG with 1064 nm wavelengthconstant energy 600 mJ, repetition rate (6) Hz and No. of pulse (150) for each sample.The pure of bulk (CdTe) and Mixture of bulk (CdTe:Cu) percentages (x=0.0, 0.3, 0.5 and 0.7)wt% were prepared. The structural, optical and morphological properties were inspected for the produced thin films.The energy band gap decreasing from 2.4 to 1.7eV with increase of Cu concentration. XRD patterns showed the domination of polycrystalline nature of cubic structure but in adding 0.5, and 0.7% Cu the nature of thin films became amorphous. AFM results demonstrated the increase of particle size from 73.66 nm to 76.67 nm at percentage of 0.5% Cu. The optical properties has been including the study of measuring the spectrum of transmittance, absorbance, Absorption coefficient (α), Optical Energy Gap (Eg), Reflectance (R), Refractive index, Extinction Coefficient, Dielectric Constant and Optical Conductivity (σ) of the wavelength range (320-1100) nm. The results have been show that the films have good transmittance for all films around 60-94% in the visible region and NIR of the spectrum that we can use them as optical windows in solar cells.

Effect of annealing on structural, morphological and optical properties of CdTe/(Cd-Zn)S thin films

Here, we present the results of an investigation on structural, morphological and optical properties of CdTe/(Cd-Zn)S films deposited on FTO substrate through electrodeposition technique for solar cell application. The deposited films were heat-treated in the presence of CdCl2 for the recrystallization. Various techniques, such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), optical studies (absorption, transmission, band-gap and photoluminescence studies) were employed to examine the structural, morphological and optical properties. XRD spectra show the preferential orientation (111) in CdTe films. Uniform and bounded grains are observed upon annealing of the films. The changes in CdTe film were attributed to nucleation of the CdTe grains during the CdCl2 treatment. The band-gap (Eg) value for CdTe estimated from absorption spectra and corresponding Tauc’s plots comes to be ~1.50eV. Summary of results suggests that the annealing of different component films is helpful in improving solar cell performance.

A Study of the Spectroscopic Performance of Laser Produced CdTe(x):S(1-x) Plasma

Abstract 
 In this work, the plasma parameters (electron temperature (Te), electron density( ne), plasma frequency (fp) and Debye length (λD)) have been studied by using the spectrometer that collect the spectrum of Laser produce CdTe(X):S(1-X) plasma at X=0.5 with different energies. The results of electron temperature for CdTe range 0.758-0.768 eV also the electron density 3.648 1018 – 4.560 1018 cm-3 have been measured under vacuum reaching 2.5 10-2 mbar .Optical properties of CdTe:S were determined through the optical transmission method using ultraviolet visible spectrophotometer within the range 190 – 1100 nm.

Structure and Optical Properties of CdTe and CdS Thin Films after Hard Ultraviolet Irradiation

The influence of hard ultraviolet radiation on the crystalline structure, surface morphology and optical characteristics of CdS and CdTe semiconductor layers obtained by direct current magnetron sputtering are investigated. It was established that the optical characteristics of the studied films CdS and CdTe are insensitive to hard ultraviolet irradiation. The crystalline structure of the CdS and CdTe layers is changed after irradiation. The period of the lattice for cadmium sulfide films increases from c = 6.77(01) Å to c = 6.78(88) Å, which may be due to the formation of point defects and defective complexes. Decrease the integral FWHM of the peaks on the X-ray diffraction patterns of the layers of CdS and CdTe was observed, due to the increase of the coherent scattering regions as a result in the process of near-surface layers partial recrystallization of the investigated films.

Effect of the combination of Cu and CdTe plasmas on the structural and optical properties of CdTe:Cu thin films deposited by laser ablation

In this work, thin films of semiconducting copper doped cadmium telluride (CdTe:Cu) were obtained by laser ablation. The effect of the combination of CdTe and Cu plasmas by the simultaneous ablation of Cu and CdTe targets, on the properties of CdTe:Cu films, when the copper plasma parameters (mean kinetic ion energy and density) are varied while CdTe plasma parameters were kept constant, is analyzed. The mean kinetic ion energy of Cu plasmas was increased from 73 to 100 eV. Cu plasma density increased linearly with mean kinetic ion energy. Mean kinetic ion energy and density of CdTe were kept constant at 75 eV and 2 × 1014 cm−3, respectively.The chemical composition was measured by energy dispersive X-ray spectroscopy. It was observed that Cu content incorporated into the CdTe lattice varied from 1.4 to 1.6 at%. Structural characterization revealed the growth of a CdTe hexagonal structure with no preferential orientation for a reference CdTe film. For samples grown combining Cu and CdTe plasmas, it was observed that increasing density of Cu plasma produces a crystalline orientation of the films in the (110) direction. Optical properties of the samples were obtained by UV–Vis spectroscopy, the data was used to estimate band gap using Tauc plots yielding values that decreased slightly form 1.47 eV for the reference CdTe film, to 1.41 eV for the film grown using the highest Cu plasma density. Scanning electron microscopy was used to study surface morphology, were rougher surfaces were observed as the Cu content in the films was increased.

Photovoltaic device performance of electron beam evaporated Glass/TCO/CdS/CdTe/Au heterostructure solar cells

Abstract We report on substrate temperature and Cu addition induced changes in the photovoltaic device performance of Glass/TCO/CdS/CdTe/Au heterostructures prepared by the electron beam evaporation technique. Prior to the photovoltaic study, the structural and optical properties of CdTe, CdTe:Cu and CdS/CdTe, CdS/CdTe:Cu layers were studied. X-ray diffraction (XRD) analysis showed that the deposited films belong to a zinc blende structure. The existence of the Te peak in the XRD pattern revealed the presence of excess Te in the deposited film structures, which confirmed the p-type conductive nature of the films. This was further substantiated by the electrical study. The low resistivity of 1 × 103 Ω cm was obtained for 4 wt.% of the Cu-doped CdTe film, which may be due to the substitutional incorporation of more efficient Cu2+ (Cd2+) into the CdTe lattice. The decrease in band gap with increasing Cu content may be attributed to the existence of shallow acceptor level formed by the incorporation of Cu into the CdTe lattice. The efficiency of the cell was increased with increasing Cu concentration and the cell prepared at room temperature with 4 wt.% of Cu addition possessed the maximum conversion efficiency of 1.68%. Further, a good photoresponse of the device is achieved as the Voc and Isc are increased with increase in the input power.

CdTe∶Eu量子点的合成及其光学性能研究

CdTe∶Eu量子点的合成及其光学性能研究

Preparation and characterization of pulsed laser deposited CdTe thin films at higher FTO substrate temperature and in Ar+O2 atmosphere

Abstract Pulsed laser deposition (PLD) is one of the promising techniques for depositing cadmium telluride (CdTe) thin films. It has been reported that PLD CdTe thin films were almost deposited at the lower substrate temperatures ( 400 °C). In this paper, CdTe layers were deposited by PLD (KrF, λ = 248 nm, 10 Hz) at different higher substrate temperatures (Ts). Excellent performance of CdTe films was achieved at higher substrate temperatures (400 °C, 550 °C) under an atmosphere of Ar mixed with O2 (1.2 Torr). X-ray diffraction analysis confirmed the formation of CdTe cubic phase with a strong (1 0 0) preferential orientation at all substrates temperatures on 60 mJ laser energy. The optical properties of CdTe were investigated, and the band gaps of CdTe films were 1.51 eV and 1.49 eV at substrate temperatures of 400 °C and 550 °C, respectively. Scanning electron microscopy (SEM) showed an average grain size of 0.3–0.6 μm. Thus, under these conditions of the atmosphere of Ar + O2 (15 Torr) and at the relatively high Ts (500 °C), an thin-film (FTO/PLD-CdS (100 nm)/PLD-CdTe (~1.5 μm)/HgTe: Cu/Ag) solar cell with an efficiency of 6.68% was fabricated.

Structural and Optical Properties of Zn Doped CdTe Thin Films by Stacked Elemental Layer Method

25% Zinc doped Cadmium Telluride thin films were prepared using Stacked Elemental Layer method. The structural studies were conducted by the X-Ray technique and the results were compared with standard data which confirmed the presence of mixed phases (CdTe, ZnTe and CdZnTe) in the stack annealed at 425°C. Transmittance spectra depicted the effect of Zn on the optical properties of CdTe thin film. The calculated band gaps from the transmittance spectra were lie between 1.42 and 1.51eV. Scanning Electron Microscope images elucidated the influence of Zn on surface morphology and the grain growth for CdTe thin films.

Formation and optical properties of CdTe∕ZnTe nanostructures with different CdTe thicknesses grown on Si (100) substrates

Atomic force microscopy (AFM) and photoluminescence (PL) measurements were carried out to investigate the formation and the optical properties of CdTe∕ZnTe nanostructures with various CdTe thicknesses grown on Si (100) substrates by using molecular beam epitaxy and atomic layer epitaxy. AFM images showed that uniform CdTe∕ZnTe quantum dots with a CdTe layer thickness of 2.5 ML (monolayer) were formed on Si (100) substrates. The excitonic peaks corresponding to transitions from the ground electronic subband to the ground heavy-hole band in the CdTe∕ZnTe nanostructures shifted to a lower energy with increasing thickness of the CdTe layer. The activation energies of the carriers confined in the CdTe∕ZnTe nanostructures grown on Si (100) substrates were obtained from the temperature-dependent PL spectra. The present observations can help improve understanding of the formation and the optical properties in CdTe∕ZnTe nanostructures with different CdTe thicknesses grown on Si (100) substrates.

EFFECT OF SUBSTRATE TEMPERATURE ON THE STRUCTURAL AND THE OPTICAL PROPERTIES OF CdTe (100) EPITAXIAL FILMS GROWN ON GaAs (100) SUBSTRATES

CdTe thin films were grown on GaAs (100) substrates by using molecular beam epitaxy at various temperatures. The results of the X-ray diffraction (XRD) patterns showed that the orientation of the grown CdTe thin films was the (100) orientation. XRD patterns, atomic force microscopy images, high-resolution transmission electron microscopy (HRTEM) images, and photoluminescence spectra showed that the crystallinity of CdTe (100) epilayers grown on GaAs (100) substrates was improved by increasing the substrate temperature. HRTEM images showed that misfit dislocations existed at the CdTe / GaAs heterointerface. These results can help improve understanding of the substrate temperature effect on the structural and the optical properties of CdTe (100)/ GaAs (100) heterostructures.

Physical properties of Bi-doped CdTe thin films deposited by cosputtering

The structural, morphological, electrical, and optical properties of CdTe–Bi cosputtered thin films related with composition are presented. The films were grown on Corning glass substrates at room temperature from a CdTe–Bi target. The composition measurements show that the Bi content in the films ranges from x = 0.0 to x = 6.37 at%, depending on the area fraction covered by the Bi piece attached to the CdTe target. The structure of the annealed films was determined from X-ray diffraction measurements. Two kinds of structures were observed, depending on the Bi content: (1) CdTe polycrystalline films containing a small amount of Bi that is probably incorporated in the Cd and Te sites of the CdTe lattice. (2) Amorphization of the polycrystalline films, with higher Bi content. From the experimental results, we concluded that using this deposition method n/p-type Bi-doped CdTe polycrystalline films can be produced with electrical resistivity between 102–103 Ω cm and electron mobility between 101 and 102 cm2 V–1 s–1. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparation and Optical Properties of CdTe and 2,4,6-tri [<i>N</i>-(4-hydroxyphenyl)maleimide]-triazine Hybrid Nanocomposites

Preparation and Optical Properties of CdTe and 2,4,6-tri [<i>N</i>-(4-hydroxyphenyl)maleimide]-triazine Hybrid Nanocomposites

Effect of thermal annealing on the interband transitions and activation energies of CdTe∕ZnTe quantum dots

The effect of rapid thermal annealing on CdTe∕ZnTe quantum dots (QDs) was analyzed to investigate the interband transitions and the electron activation energy. The full width at half maximum of the photoluminescence (PL) peak corresponding to the interband transitions from the ground electronic subband to the ground heavy-hole band (E1‐HH1) in the CdTe∕ZnTe QDs annealed at 330°C decreased, and their integrated PL intensity of the E1‐HH1 transition peak significantly increased. The activation energy of electrons confined in CdTe∕ZnTe QDs annealed at 330°C increased as high as 77meV, which was the highest value among the as-grown and annealed samples. These results indicate that the crystallinity of the CdTe∕ZnTe QDs is improved by annealing, and the present results can help improve the understanding of the thermal annealing effect on the optical properties of CdTe∕ZnTe QDs.

Determination of thermal and optical parameters of the semiconductor CdTe by photopyroelectric spectroscopy

In this study, photopyroelectric spectroscopy was used to obtain thermal and optical properties of CdTe in the 300 < λ < 1200 nm wavelength range, where λ is the wavelength. The normalized photopyroelectric intensity signal V n (λ) and its phase F n (λ) were independently measured, as well as the intensity V n (f) and the phase F n (f) (f being the chopping frequency) for a given λ of the saturation part of the PPES spectrum. Equations of both the intensity and the phase of the PPES signal, taking into account the thermal and the optical characteristics of the pyroelectric (PVDF) detector, were used to fit the experimental results. From the fitting in the graph F n (f) versus f, we obtained, with great accuracy, the value of thermal diffusivity coefficient a. From the fitting in the graph V n (f) versus f, we obtained the thermal conductivity k. The specific heat c of the sample is then directly derived from the relation k = ρcα, where p is the mass density, valid for a stationary slate. From the fittings in the graphs V n (λ) versus λ and F n (λ) versus λ, we obtained the optical absorption coefficient and the optical gap of the CdTe.