CdS:Cu nanocrystalline films were prepared by chemical bath on glass substrates at a deposition temperature of 80°C. Different Cu-doping levels were obtained by changing the volume of the Cu-reagent-solution into the CdS growing solution. X-ray diffraction ͑XRD͒ and optical absorption ͑OA͒ measurements were carried out to characterize the material. From the XRD patterns it is concluded that grains in undoped films grow in the wurtzite hexagonal phase, and in Cu-doped films they grow in the zinc blende cubic phase. The average grain size, located in the range 14-23 nm, was calculated by employing Scherrer's formula. From OA spectra the forbidden energy bandgap ͑E g ͒ was determined by using the ͑␣h͒ 2 ϰ ͑E g -h͒ relation, where ␣ is the OA-coefficient and h the photon energy. Due to the doping, E g shifts to lower values depending on the impurity level of the film. Furthermore, the dependence of E g with radius size and interplanar distances of the lattice is discussed. Gibbs free energy calculation for the Cu doping CdS process is also included.
Nanocrystalline CdSe films were grown onto glass substrates by the chemical bath method. Different constant deposition temperatures (T d ) were employed in the range 4-65 ºC. Average grain size (GS) increased monotonically with T d , reaching saturation at~65 ºC. The GS values were in the interval 5-16 nm. At low T d values (4-15 ºC), the structural phase was hexagonal wurtzite (W), for intermediate values, a wurtzite and zincblende (ZB) mixture of phases was found, and at high T d (65 ºC) only cubic ZB phase was present in the layers. The variation of the bandgap as a result of the structural phase change and quantum confinement is studied.
Cadmium sulfide thin films were prepared by chemical bath on glass substrates at 80°C. CdS was Er-doped during the growth process by adding water-diluted Er(NO3)33∙H2O to the CdS aqueous growing solution. The relative volume of the doping solution was varied in order to obtain different doping levels. The crystalline structure of CdS:Er films was cubic zinc blende for all the doped layers prepared. The (111) interplanar distance has an irregular variation with the Er doping level. Consequently, the band gap energy (Eg) firstly increases and afterward diminishes becoming, at last, approximately constant at around Eg=2.37eV. For higher doping levels, in the as-grown films, dark electrical conductivity (σ) values reach 1.8×10−2Ω−1cm−1 at room temperature. The logarithm of σ vs 1∕kT plot, where k is Boltzmann’s constant and T the absolute temperature, indicates an effective doping of CdS as a result of the Er introduction into the lattice of the material. Hall effect measurements reveal a n-type doping with 2.8×1019cm−3 as maximum carrier density.
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