ABSTRACT
The high-quality n-type CdS on a p-type Si (111) photodetector device was prepared for the first time by a one-pot method based on an ns laser ablation method in a liquid medium. Cadmium target was ablated in DMSO solution, containing sulfur precursor, and stirred, assisting in 1D-growth, to create the sulfide structure as CdS nano-ropes form, followed by depositing on the Si-substrate by spin coating. The morphological, structural, and optical characteristics of the CdS structure were examined using X-ray diffraction, transmission, and scanning electron microscopy, photoluminescence, and UV-VIS spectroscopy. From X-ray diffraction analysis, the growing CdS spheres have a good crystal nature, with a high purity and desired c-axis orientation along the (002) plane, and the crystallinity was around 30 nm. According to optical characterization, high transparency was found in the visible-near-infrared areas of the electromagnetic spectrum, and the CdS spheres have a direct optical energy band gap of 3.2 eV. After that, the CdS/Si hetero-structured device was found to be improved remarkably after adding CdS. It showed that the forward current is constantly linear, while the dark current is around 4.5 µA. Up to a bias voltage of 4 V, there was no breakdown, and the reverse current of the heterojunctions somewhat increased with reverse bias voltage, while the photocurrent reached up to 580 and 690 µA for using 15 and 30 W/cm2 light power, respectively. Additionally, the ideal factors for CdS/Si heterojunction were 3.1 and 3.3 for 15 and 30 W/cm2 light power, respectively. These results exhibited high performance compared to the same heterojunction produced by other techniques. In addition, this opens the route for obtaining more enhancements of these values based on the changing use of sulfide structures in the heterojunction formation.
ABSTRACT
ZnO/MWCNTs nanocomposite has significant potential in photocatalytic and environmental treatment. Unfortunately, its photocatalytic efficacy is not high enough due to its poor light absorbance and quick recombination of photo-generated carriers, which might be improved by incorporation with noble metal nanoparticles. Herein, Ag-doped ZnO/MWCNTs nanocomposite was prepared using a pulsed laser ablation approach in the liquid media and examined as a degradable catalyst for Rhodamine B. (RhB). Different techniques were used to confirm the formation of the nanostructured materials (ZnO and Ag) and the complete interaction between them and MWCNTs. X-ray diffraction pattern revealed the hexagonal wurtzite crystal structure of ZnO and Ag. Additionally, UV-visible absorption spectrum was used to study the change throughout the shift in the transition energies, which affected the photocatalytic degradation. Furthermore, the morphological investigation by a scanning electron microscope showed the successful embedding and decoration of ZnO and Ag on the outer surface of CNTs. Moreover, the oxidation state of the formed final nanocomposite was investigated via an X-ray photoelectron spectrometer. After that, the photocatalytic degradations of RhB were tested using the prepared catalysts. The results showed that utilizing Ag significantly impacted the photo degradation of RhB by lowering the charge carrier recombination, leading to 95% photocatalytic degradation after 12 min. The enhanced photocatalytic performance of the produced nanocomposite was attributed to the role of the Ag dopant in generating more active oxygen species. Moreover, the impacts of the catalyst amount, pH level, and contact time were discussed.
