Fabrication of thin film Ag/AgCl reference electrode by electron beam evaporation method for potential measurements
Tien Minh Huynh, Tung Son Vinh Nguyen, Tin Chanh Duc Doan and Chien Mau Dang
Abstract
In this study the novel approach for fabricating thin film Ag/AgCl electrodes was proposed using electron beam evaporation method for potential measurements as reference electrodes. A silver and silver/silver chloride (Ag/AgCl) thin films with a thickness of 300 nm were evaporated on the silicon substrate which had been initially oxidized to create the insulating silicon dioxide (SiO2) layer. The dimension of the electrodes was about 0.5 mm × 2.0 mm. The characterization of AgCl layers was performed with field emission scanning electron microscopy, x-ray diffraction and energy dispersive x-ray spectroscopy, Raman spectroscopy and optical microscopy. The open circuit potential (OCP) measurements in buffer solution pH 7 were investigated between the fabricated Ag/AgCl electrodes and a commercial Ag/AgCl electrode as the reference electrode. The measured OCP values had insignificant disparity. The good reproducibility and potential stability with the average potential value and deviation were within 334.0 mV ± 4.07 mV. In addition, a pH sensing test was also performed by using a laboratory-made potentiometer, which showed a sensitivity of 48.01 mV pH−1, with the correlation coefficient being greater than 0.99. The results showed that the fabricated thin film Ag/AgCl electrodes which could be obtained by a simple and fast process had high purity and could be used as reference electrodes for potential measurements
