Prevention of degradation of (Ba,Sr)TiO3 during forming gas anneal by a SiO2 capped (Ba,Sr)RuO3 electrode

Degradation of $(\mathrm{Ba,Sr}){\mathrm{TiO}}_3$ during a forming gas anneal was examined and the effect of a ${\mathrm{SiO}}_2$ capped $(\mathrm{Ba,Sr}){\mathrm{RuO}}_3$ electrode was studied. All the samples were prepared by a rf magnetron sputtering technique and the forming gas $\text{(10\%\hspace{0.17em}}{\mathrm{H}}_2\text{+90\%\hspace{0.17em}}{\mathrm{N}}_2)$ anneal was carried out at 400 °C for 30 min. The $(\mathrm{Ba,Sr}){\mathrm{RuO}}_3$ film directly exposed to ${\mathrm{H}}_2$ ambient was damaged severely, which resulted in the reduction and phase separation into BaO and Ru. On the other hand, the ${\mathrm{SiO}}_2$ capped $(\mathrm{Ba,Sr}){\mathrm{RuO}}_3$ film was not damaged during ${\mathrm{H}}_2$ annealing. By adopting the ${\mathrm{SiO}}_2$ capped $(\mathrm{Ba,Sr}){\mathrm{RuO}}_3$ as an electrode of $(\mathrm{Ba,Sr}){\mathrm{TiO}}_3,$ the degradation of $(\mathrm{Ba,Sr}){\mathrm{TiO}}_3$ could be inhibited. ${\mathrm{SiO}}_2$ capping also decreased the extent of the reduction of a ${\mathrm{Pt/(Ba,Sr)TiO}}_3/\mathrm{Pt}$ structured capacitor, which is known to degrade dramatically. It is believed that the major cause of the tolerance to the forming gas anneal is the blocking capability of ${\mathrm{SiO}}_2$ against the diffusion of reaction products such as ${\mathrm{H}}_2\mathrm{O}.$