The effect of complexing agent on crystal growth, structure and properties of nanostructured Cu2−xS thin films

Thin films of Cu2−xS (x = 0, 1) were deposited on self-assembled, monolayer modified substrates in the copper–thiosulfate system with various concentrations of ethylene diamine tetraacetic acid (EDTA) at a low temperature of 70 °C. The thin films were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). The optical and photoelectrochemical (PEC) properties of the Cu2−xS semiconductor films were investigated by ultraviolet–visible (UV–vis) absorption spectroscopy and a three-electrode system. It is found that EDTA plays a key role in the process of Cu2−xS nanocrystals formation and growth. The compositions of the Cu2−xS nanocrystals varied from Cu2S (chalcocide) to CuS (covellite) through adjusting the concentration of EDTA, which is used as a complexing agent to yield high-quality Cu2−xS films. The growth mechanisms of Cu2−xS nanocrystals with different EDTA concentrations are proposed and discussed in detail.

Graphical abstractThe molar ratio between EDTA and CuSO4·5H2O is shown to greatly affect the shape and size of Cu2−xS nanocrystals.Figure optionsDownload full-size imageDownload as PowerPoint slide