Hydrogen reduction of a RuO2 electrode prepared by DC reactive sputtering

RuO2 thin films deposited by reactive DC sputtering were heat-treated in a 0.3%-H-2 atmosphere at 200 degrees C in order to investigate the reduction property of RuO2. The films were selectively reduced (starting from the int erface) because of insufficient oxidation. When the as-deposited RuO2/Si st ructure was hydrogen-reduced, the RuO2 film was broken into fragments becau se of poor mechanical strength. On the other hand, the RuO2 film heat-treat ed once in O-2 at 700 degrees C cracked into a star shape as a result of va por generation and volume shrinkage. The star-shape cracking was still obse rved even when the RuO2 film was covered with a 90-nm-thick BST film. The m echanical strength and the adhesion of RuO2 were improved to some extent by post-oxidation at high temperatures. However, a way to prevent the morphol ogical destruction could not be found because of the thermodynamic equilibr ium during the hydrogen reduction process. (C) 2000 Kluwer Academic Publish ers.