Papers by Keyword: CdTe

Abstract: the equilibrium lattice constants, elastic and thermodynamic properties of cubic CdTe are systemically investigated at high temperature using the plane-wave pseudopotential method as well as the quasi-harmonic Debye model. The bulk modulus of CdTe are calculated as a function of temperature up to 1000K, the relationship between bulk modulus B and pressure is also obtained. The results gained from this model will provide overall predictions accurately for the temperature and pressure dependence of various quantities such as the bulk modulus, the heat capacity and the thermal expansion coefficient. More over, the dependences between Debye temperature and temperature are also successfully obtained. Our results are compared with the experimental data and discussed in light of previous works.

Abstract: A water-soluble CdTe QDs capped by 3-Mercaptopropionic acid (MPA) were synthesized. The results confirmed that the grain size of the QDs was controlled by changing the reflux time of precursor solution and that the QDs possessed obviously quantum size effect. The results showed that a depletion layer CdTe_1-xS_x (0£x≤1) formed in between CdTe nanoparticle and ligand MPA. It is believed that two heterojunction-like structures possess quite distinct surface photovoltaic characteristic excited between the core-CdTe and the shell-CdS, and between CdTe/CdS and the ligand MPA, respectively, according to the EFISPS results of the MPA-capped CdTe QDs.

Abstract: Thermal neutron detector is developed by using Cadmium telluride (CdTe) semiconductor, due to large thermal neutron capture cross section of Cd. The developed detector demonstrated the occurrence of the 96 keV gamma ray emissions from 113Cd(n, γ) 114Cd reaction.

Abstract: Dysprosium (Dy) ion implanted CdTe polycrystalline thin film (PTF) deposited on the ceramic substrate by the close spaced sublimation （CSS) method. Both the energy dispersive X-ray spectrometer（EDS）and Raman scattering analysis show that the as-deposited and Dy ion implanted CdTe PTF are non-stoichiometric with excess telluride. Furthermore, X-ray diffraction study reveals that the CdTe PTF forms a zinc-blended structure. In the Raman scattering analysis, the position of the peak on implantation does not change apparently whereas the intensity of the peak decreases owing to the lattice damage and increases as a result of thermal annealing. The data support that Raman activity is enhanced after Dy ion implantation.

Abstract: We report the structural and photoluminescence properties of CdTe/Porous silicon (PS) composite system prepared by chemical vapor deposition. The XRD pattern accord with the standard pattern of cadmium telluride of the samples was evaluated and the morphology of CdTe particles was characterized by scanning electron microscopy. The composite sample gives a strong luminescence and the mechanism of photoluminescence with CdTe/PS has also been discussed.

Abstract: This paper reports the preparation of exceptionally high brightness CdTe quantum dots (QDs) that gives emission in the range of green to red by simply prepared them in a binary mixture of octadecyl phosphonic acid (ODPA) and oleic acid (OA) surfactants. By easy controlling the ratio between the two surfactants in the reaction, the QDs with unique emission, high -brightness and -quantum yield (QY), ca. 63, 87 and 89% for green, yellow and red QDs respectively, can be obtained. Owing to their unique PL and high QY, the CdTe QDs should find an extensive uses in the currently existing applications.

Abstract: The peculiarities of photo-electric processes in thin film CdS/CdTe solar cells (SC) with different back electrodes (Cu/Au, ITO, Cu/ITO) have been studied. As it was established by capacitance – voltage (C – V) characteristics, the potential barrier heights for CdTe/Cu/Au and CdTe/ITO were 0.3 eV and 2.2 eV, respectively. The concentrations of charge carriers near back contact consisted 91020 m–3 and 21021 m–3, respectively. A high carrier concentration and high potential barrier of the ITO back contact caused the tunnel – recombination mechanism of the charge transport. The investigations of CdS/CdTe/ITO SC spectral photosensitivity testify a negative impact of the developed grain-boundary surface of the base layer on the processes of diffusion and separation of non-equilibrium current carriers generated by short-wave radiation. It is shown that the deposition of Cu nanolayer before the deposition of ITO films give stable efficiency 10 % for bifacial CdS/CdTe solar cells.

Abstract: Thin films of CdTe semiconductors were prepared on sapphire single crystal and quartz glass substrates by a vacuum evaporation method. Crystallinity and photoluminescence properties of the obtained CdTe thin films on the substrates were semi-quantitatively compared concerning the difference of the substrate materials. Dependences of the properties on the substrate temperature in the preparations and indium doping to the thin films were also investigated.

Abstract: Bulk compounds of CdTe, Cd0.25Sn0.75Te and Cd0.25Te0.75Sn have been prepared by direct reaction of their high purity (99.9999%) elemental constituents employing rotating furnace. The hot wall system is optimized for the deposition of prepared alloys by using molecular flow studies with Monte Carlo simulation technique. Thin films have been deposited on well cleaned glass substrates using the prepared alloys by the optimized hot wall vacuum evaporation system. The compositions of the prepared bulk and thin films have been identified using energy dispersive X-ray analysis. The compositions are found to be same for both the bulk and thin films as the prepared alloys. The structural properties of the deposited films have been studied using X-ray diffraction technique. The results show that all the films are crystalline in nature and the peaks in the XRD graph of CdTe correspond to cubic zinc blende structure and that of Cd0.25Sn0.75Te and Cd0.25Te0.75Sn compounds to rock salt structure. The lattice parameters and grain sizes of all the films have been evaluated. The surface morphology of the thin films is studied using Scanning Electron Microscope (SEM). The SEM analysis shows that surface of the films are smooth and crystalline in nature. The optical transmittance spectra of thin films were recorded using spectrophotometer in the range of wavelength from 190 nm to 2500 nm. All the films exhibit direct optical band gap and their values are 1.45eV (CdTe), 0.9eV (Cd0.25Sn0.75Te) and 1.1eV (Cd0.25Te0.75Sn). Thicknesses of the thin films have been determined by multiple beam interferometric technique.

Abstract: A kind of novel quantum dots (QDs) with poly(4-vinylpyridine) (PVPy) as shell and CdTe QDs as core was presented in this work. This core/shell ODs can conjugate DNA easily because the surface pyridyl exist on QDs, and which has potential application in DNA biosensors field. CdTe QDs were prepared in aqueous solution with 3-mercaptopropionic acid (MPA) as stabilizer. It was found that the fluorescent intensity of QDs was depended the reflux time. Following the increase of reflux time, the fluorescent intensity of QDs reached the maximum at 10 h with about 10 nm in diameters. And the fluorescent intensity of QDs was also increased. When the reflux time was 10 h, the diameter of QDs would increase to about 10 nm. After adjusted the pH of QDs solution system to 7.0, the MPA stabled QDs were purified by ultracentrifugation and freeze-drying respectively. The polymerization was performed in water when 4-vinylpyridine (VPy) used as monomer, N,N’-methylene-bisacrylamide (MBAAm) as crosslinker, potassium persulphate (PPS) as initiator and MPA stabled QDs as seeds. The surface carboxyl of MPA on QDs could promote the form of PVPy coated CdTe QDs. It was shown that the fluorescent intension of core/shell QDs was decreased following the polymerization and the diameter of QDs could increase to 20-30 nm.