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

• Published in: Chinese chemical letters 2014-11, Vol.25 (11), p.1473-1478
• Main Authors: Lu, Yong-Juan, Jia, Jun-Hong
• Format: Article
• Language: English
• Subjects: Chemical synthesis; Optical properties; Photoelectrochemical properties; Thin film
• ISSN: 1001-8417; 1878-5964
• DOI: 10.1016/j.cclet.2014.06.003

The molar ratio between EDTA and CuSO4·5H2O is shown to greatly affect the shape and size of Cu2−xS nanocrystals. 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.