Characterization of chemical-bath-deposited CdS thin films doped with methylene blue

Abstract

The optical and electrical properties of methylene blue-doped CdS films, grown by chemical bath deposition, have been studied. Doping was achieved by adding specific volumes of methylene blue (MB) diluted in distilled water to the chemical bath. X-ray diffraction patterns display the zincblende crystalline structure for all the CdS samples, with a remarked preferred orientation along the (111) direction. The interplanar distance among the (111) planes indicates a minimum value when the relative volume (VR) of MB in the growing solution is about 7%. Photoacoustic absorption spectra show an evolution of the CdS band-gap energy (Eg) when VR increases, indicating adsorption of MB on the CdS microcrystals. Starting from an Eg of 2.42 eV for the undoped sample, an Eg value of nearly 2.49 eV is reached for the sample doped with VR=7% of MB. For higher concentrations, no increase is observed, showing rather a saturation effect. Dark conductivity (σ) measurements at room temperature (RT) display an increase of the conductivity from 1×10−4 Ω−1 cm−1, for the undoped film, up to 3.0×10−2 Ω−1 cm−1 for the highest doping value reached, that is when VR=7%. Thermoelectrical power measurements carried out at RT indicate that the layers are n-type doped, with a density of carriers (n) whose data basically oscillate in the range (5.3±1.3)×1016 cm−3. An exception is found for the sample with VR=7%, for which a value of n=1.02×1017 cm−3 is measured.

Influence of L-Tryptophan on Growth and Optical Properties of PbS Nanocrystalline Thin Films

“…Some other reports of doping with metalorganic compounds in PbS have shown results that attract attention by charge transfer along with structural and optical changes [11], a phenomenon that establishes the importance of doping with different organic molecules. However, doping with organic molecules is still in the preliminary stage since only few reports have been published with CdS [12] and CdO [13].…”

Photoluminescence properties of the ZnO–CdO–TeO2 system doped with the Tb3+and Yb3+ ions

“…2 illustrates a (PAS) 2 versus hn typical plot for the E g calculation. PA has been successfully used to measure E g in other type of materials [16][17][18]. It can be observed how the E g value is limited to take values in the interval 3.47-3.60 eV, which seems to be in agreement with E g ¼ 3.9 eV of CdTeO 3 [10,15].…”