Iridium/Carbon Films Prepared by MOCVD

Abstract

gas sensors because of their unique physical and chemical properties, such as their inertness, good oxidation resistance, electrical conductivity and catalytic performance. However, due to sluggish charge transfer reactions at the sensing electrode interface at low temperature (less than 500oC) (1), a gas sensor constructed with traditional Pt electrodes and ZrO2 electrolyte needs to be heated to a higher temperature to obtain sufficient voltage output and a shorter response time. In order to improve the properties of these sensors, Ir cluster films have been prepared by MOCVD (metalorganic chemical vapour deposition) and investigated (2–8). This paper reports on the composition, structure and electrochemical properties of some Ir/C films. Experimental Procedure A schematic diagram of a horizontal hot-wall MOCVD apparatus is shown in Figure 1. The precursor for the Ir/C films was 500 mg of iridium tris-acetylacetonate, (CH3COCHCOCH3)3Ir, Ir(acac)3. Oxygen and argon were used as the reactant and transmission gases, respectively. The substrates were quartz (10 mm × 10 mm × 1 mm thick) and YSZ (yttria stabilised zirconia): 6 mol % Y2O3, (10 mm Φ × 2 mm thick). The temperature of the precursor (Tsor) was kept at 190oC. The total gas pressure in the chamber was fixed at 500 Pa, with argon flow maintained at 50 ml min. The precursor was placed in a small quartz boat in the MOCVD apparatus. The deposition temperature (Tdep) was varied from 450 to 650oC, for a deposition time of 60 minutes. The flow of oxygen (FO2)