Abstract
Cr nano-porous electrode film filter could be prepared by co-sputtering Cu and Cr, followed by annealing for 1 h at 573 K and dealloying for 15 h in 32.5% HNO3. Its pore-sizes depend on initial Cu-Cr compositions. To control pore sizes of the nano-porous Cr thin film, initial Cu-Cr compositions for the fabrication conditions was researched by using combinatorial technique. We investigated a wide compositional range between 32 and 22 at.% Cr. Between 28 and 22 at.% Cr, dealloying produces low residual Cu composition ratio less than 10 at.%. The pore sizes obtained were <20 nm for 32 at.% Cr, 20-40 nm for 28 at.% Cr, 40-60 nm for 25 at.% Cr and >60 nm for 22 at.% Cr. The initial composition ratio of 28 at.% Cr was tested for fabricating a Cr nano-porous electrode film filter for a moisture sensor which takes sandwich structure of the nano-porous Cr thin film/polyimide film/Ag electrode. The final residual Cu composition ratio was 17 at.%, not less than 10 at.%, because of using a thin film with uniform composition. The changes in electrostatic capacity of the moisture sensor to changes in relative humidity (50%RH-90%RH) was studied, and the sensor exhibited the followability to changes in relative humidity in the air.
