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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7682-7687 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of stable crystalline phases of the Cd–Te–O ternary system were prepared by thermal annealing in an Ar flux of amorphous CdTe:O films. The composition of the annealed films depended on the initial oxygen content in the film, the temperature and duration of the annealing process. The annealed films were characterized by means of x-ray diffraction spectroscopy and by optical absorption spectroscopy. The results show that for low oxygen content in the as grown film and high annealing temperature, the CdTe cubic phase is the predominant crystalline phase in the annealed film. For intermediate oxygen content in the as grown film, the result obtained after the annealing process is a composite material consisting in the mixture of both CdTe and CdTeO3 crystallites. The variation of the annealing temperature produces changes in the size of the crystallites of both crystalline phases. It also can change the CdTe to CdTeO3 proportion in the films. For low annealing temperature, the size of the CdTe crystallites in the film is 〈14 nm, the exciton Bohr diameter in CdTe. The optical characterization of the CdTe–CdTeO3 composite material shows that this system is very suitable for the study of optical transitions in the electronic band structure of CdTe. Furthermore, for the films with the smallest CdTe crystallites it is possible to observe the effects in the CdTe band structure produced by the reduction in the size of the CdTe crystallites to a dimension comparable to the exciton Bohr diameter. The annealing process in the as grown films with high oxygen content produces films composed by a mixture of the oxide insulating phases CdTeO3 and CdTe2O5. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3908-3911 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Investigations of trapping centers have been carried out in CdTe polycrystalline films by using the thermally stimulated conductivity (TSC) technique. The measurements were performed in the temperature range from 80 to 300 K. The TSC spectra showed three peaks related to three trapping levels with energy activations of 0.18, 0.29, and 0.32 eV, respectively. The two first trapping levels correspond to known acceptor centers in bulk CdTe previously reported. It is suggested that the level at 0.32 eV is due to grain boundary defects characteristic of the polycrystalline films. The main parameters of these trapping centers have been determined by using known theoretical relations. The temperature dependence of the dark resistivity indicates that the impurity conduction does not make an important contribution to the TSC spectra of the films. From these measurements an activation energy of 0.49 eV for the conductivity of the films was found. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5461-5463 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Homogeneous thin films of a-CdTe:O were thermal annealed in an Ar flux. The as-grown samples have an amorphous structure. The annealed films crystallize to a mixture of both CdTe and CdTeO3. For low annealing temperatures (less than 100 °C) it is possible to get CdTe crystallites with sizes smaller than 14 nm. In this work we report measurements of x-ray diffraction and optical absorption spectra of these films. The x-ray diffraction patterns of the films were used to study the CdTe crystallization process as a function of the annealing temperature. The CdTe crystallite size of the films was determined from the diffraction patterns using the Debye–Scherrer formula. It was observed that the CdTe crystallite size increases with annealing temperature. The optical absorption spectra of the films with the smallest CdTe crystallite size show how the absorption band edge of CdTe is shifted by the effects of the crystallite size. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 3254-3256 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The critical volume fraction for conductivity percolation in the di-phasic system (CdTe)1−x Tex has been determined using atomic force microscopy. The onset for rapid increase in the electrical conductivity is found at a volume fraction of Te of about 0.4. According to previous theoretical calculations this value is characteristic of a system with two-dimensional symmetry. It is also found that the Te phase grows in the form of columns, which explains the observed critical volume fraction value for percolation in the conductivity measurements. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Using a radiofrequency sputtering deposition technique, ternary Cd0.18Sb0.64Te0.18 thin films have been grown on glass substrates at several substrate temperatures (50–250°C). The samples have an Sb content of about 63 at %, as measured by Auger spectroscopy. The surface roughness, the structural and the electrical properties of the films were studied as a function of substrate temperature. X-ray diffraction (XRD) measurements showed that the structure of the films changes from an amorphous phase, when deposited at lower substrate temperatures, to a mixture of two crystalline phases (CdTe and Sb) for higher substrate temperatures. Atomic force microscopy shows an increase in the surface roughness with an increase in the substrate temperature, clearly showing the formation of crystalline phases with microcrystallite sizes in good agreement with those determined from XRD measurements. The amorphous-to crystalline transition is accompanied by an abrupt increase in the room temperature electrical conductivity of the films. This increase in the conductivity as well as its temperature dependence in the range of room temperature to 150°C can be understood in terms of an electrical percolation process through the conducting Sb crystallites.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 17 (1998), S. 1099-1102 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 25 (1994), S. 203-207 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Oxygenated CdTe films prepared by r.f. sputtering have been shown to have band gap energies between 1.48 and 3.35 eV, depending on the amount of oxygen incorporated in the CdTe matrix. Samples with oxygen concentrations above 7 at.% are amorphous, whereas those with oxygen concentrations below 7 at.% are polycrystalline, as determined by x-ray and Raman measurements. The Raman spectra of the polycrystalline samples show that there is ca. 4 at.% Te in the form of inclusions under high pressure, which is relatively easy to detect owing to the enhanced Raman cross-section of Te. The Raman spectra of the amorphous samples is dominated by a single broad band at 159 cm -1. The fact that tellurates in general show a similar band, in spite of their different vibrational density of states, indicates that it corresponds to Te—Te bonds in the amorphous matrix.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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