CdS_xTe_1-xfilms: preparation and properties

Abstract

CdSxTe1-x films (0<x<1) were deposited by simultaneous evaporation of CdS and CdTe powders from a vertical two-zone hot wall evaporation jig onto glass substrates. Electrical conductivity, thermoelectric and optical properties along with microstructural properties were studied in order to derive information on the electron transport processes in the films. Raman scattering was also studied for the films.

S-Rich CdS1−yTey Thin Films Produced by the Spray Pyrolysis Technique

“…The explanation of these results is complicated, because the values of y obtained by the EDS analysis are not trustworthy, and because of the differences in indium content of the films. The effect of increasing indium content is to increase the bandgap, or in other words, to shift the minima to lower wavelengths, but qualitatively these results have a trend that is consistent with the model used by Ohata et al [30] and Pal et al [31], which they obtained for the bandgap of the Te-rich CdS x Te 1´x alloy. In this model, the bandgap of the alloy can be predicted using a simple quadratic equation:…”

“…The explanation of these results is complicated, because the values of y obtained by the EDS analysis are not trustworthy, and because of the differences in indium content of the films. The effect of increasing indium content is to increase the bandgap, or in other words, to shift the minima to lower wavelengths, but qualitatively these results have a trend that is consistent with the model used by Ohata et al [30] and Pal et al [31], which they obtained for the bandgap of the Te-rich According to Nȇmec et al [38], these minima are in good agreement with the splitting of the valence band (A, B, C) at the centre of the Brillouin zone which is typical of the bulk CdS in hexagonal structure. This confirms that the CdS:In films under study in this work also contain the hexagonal phase, which is consistent with the XRD diffractograms.…”

“…The three films are polycrystalline, but the difference between the morphologies of the CdS:In film and the CdS 1− yTey films is apparent. [31] who found a shift in the position of the (002) peak in the XRD diffractograms of CdS x Te 1´x films from 2θ = 24.3˝to 25.3˝with change in composition (0.1 < x < 0.8). Birkmire et al [5] who studied the diffusion of S in CdTe films reported a shift in the position of the C(111) peak of CdTe towards larger 2θ values and found a decrease in the lattice parameters of the CdTe/CdS cells after CdCl 2 heat treatment.…”

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“…3 shows the positions of the PL peaks as a function of depth through the CdTe layer. Following the work of Ohata et al [26] and Pal et al [27] the bandgap of the mixture CdS x Te 1Àx follows the empirical formula:…”

“…The solid solution has a minimum bandgap at x 0.25 which is 80 meV below the CdTe bandgap at 10 K. If k 1.7 eV from Pal et al [27] then the molar fraction x of sulfur in the CdTe can be estimated based on the shift to lower energies of the 1.38 eV peak, assuming that it is entirely due to sulfur diffusion. This gives a range of sulfur diffusion pro®les, which are shown in Fig.…”