Analysis of Electrodeposited Au-Ni Alloy Films for Carbon Inclusion and Crystallinity

Carbon inclusion and its effect on the crystallinity of electrodeposited Au-Ni alloy films are discussed based on the results of X-ray diffraction (XRD) spectroscopy, chemical composition analysis, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Under an optimum set of conditions, both citrate bath and pyrophosphate bath yield Au-Ni alloy deposits, which are amorphous to the XRD measurement. The carbon content of the amorphous deposit is higher than that of the crystalline deposit, and this trend is observed for deposits from both citrate and pyrophosphate baths. Experimental results are presented, showing that the amorphous deposits from both citrate and pyrophosphate baths contained a comparable amount of carbon, which indicates that CN from KAu(CN)(2) is the major source of carbon inclusion in the deposits from both baths. The results of XPS and, more clearly, Raman spectroscopy show that the amorphous Au-Ni deposit contains a large amount of carbon in the amorphous state, which apparently forms as a result of the decomposition of CN, whereas only the crystalline deposit contains carbon in the form of CN. It is concluded that carbon inclusion and the state of included carbon play a significant role in the process of creating the amorphous structure of Au-Ni alloy electrodeposits.