Room Temperature Oxidation of Ruthenium

With scanning tunneling microscopy (STM) we studied the initial oxidation of Ru(0001) at room temperature using atomic oxygen (O') as oxidizing agent. Even at 300 K, Ru oxide clusters are formed and are located preferentially at single step edges and less likely at double steps and on the flat terrace. The observed Ru-O cluster formation indicates a nucleation and growth process. The cluster formation at room temperature implies that the supply of Ru atoms is not rate limiting in the initial oxidation of Ru(0001). A mobile surface Ru-O precursor species has to be postulated for explaining the observed nucleation and growth process. A mobile surface Ru-O precursor species is considered to be equally involved in the oxidation of Ru with molecular oxygen and the oxidation under electrochemical conditions.