Study Of Preparation And Optical Properties Of Copper Sulfide Powders And Thin Films

As a kind of important semiconductor materials, Copper sulfides have beenwidely studied for their significant electronic and optical properties, which areconsidered to have potential applications in solar cells, sensors, nanoswitchesand photocatalysts. In this paper, a facile, green and microwave-assistedhydrothermal method was used to prepare CuS micro/nano crystals and films.The influences of precursor ratios, reaction times, temperatures and pH valueswere investigated to control the products microstructures by applying differentsurfactants. The products phases, microstructures, crystal structures, surfacemorphology, and optical properties were characterized by X-ray diffractometer（XRD）, Field emission scanning electron microscope （FE-SEM）, Transmissionelectron microscope （TEM）, Atomic Force Microscope （AFM） andUltraviolet–visible-near Infrared spectroscope, respectively. The results showthat:（1）The CuS particle crystallinity was found increasing with longer reactiontimes and higher reaction temperatures, where corresponding morphologychanges from flower-like round spheres to rod-like structures. It was found thatCuS particles with pure hexagonal phase could be obtained when pH values werelower than2.5or higher than8. The CuS particles morphology was controlled bychanging the S/Cu ratios without using any templates. When the S/Cu ratioswere controlled from3to7, the obtained morphology were found changing fromsheets-assembled hollow spheres-like structures to flower-like structures, andfinally to hexagonal sheets-like crystals.（2）PVP was used to obtain different morphologies of CuS, such as onedimensional chains and rods, three dimensional rings, assembled cages andhollow spheres-like structures with characterization of corresponding opticalproperties. Possible growth mechanism was proposed by studying the influencesof different reaction times, PVP concentrations, S/Cu ratios and reaction solvents on the product morphology.（3）Nanosheets-assembled flower-like CuS particles were obtained by addingCTAB as the surface active agents. These flower-like CuS particles exhibituniform sizes, good diversity, and high specific surface area. The particle sizesof the flowers could be changed by using different CTAB concentrations. Bycomparing to the bulky CuS particles, the as-obtained products were found tohave obvious different optical performances in the UV-vis spectra, which exhibitmuch higher absorbencies with wider absorption ranges. By combining theoptical properties and high surface area of the CuS flowers together, it reveals agreat potential use of these particles in photocatalytic fields.（4）Two approaches, chemical bath deposition and microwave hydrothermalmethods, were employed to prepare dense, uniform CuS films on the glasssubstrate using Cu（NO₃）₂·3H₂O and C₂H₅NS as the raw materials andEDTA-2Na as the complexing agents. The influences of reaction time andtemperature during the microwave hydrothermal process were studied. Resultsshow that when increasing reaction temperatures, the films were found to containbigger particles sizes with higher crystallinity; when prolonging reaction times,the films were observed to be obviously thicker with higher roughness. Bycomparing to chemical bath deposition method, microwave hydrothermalprocess could greatly shorten the reaction time with distinct improvement of thefilm crystallinity.