Effect of the Strain from the Substrate on Tunability of(100) One-axis Oriented (Ba0.5Sr0.5)TiO3 Thin Films

The impact of the residual strain induced by the thermal strain on the dielectric tunability was systematically studied for (100)-one-axis-oriented polycrystalline (Ba
_0.5
Sr
_0.5
)TiO
₃
films. These films were grown on various substrates with different thermal expansion coefficients [a
_(sub.)
] covered with a stack of (100)
_c
SrRuO
₃
/(100)
_c
LaNiO
₃
/(111)Pt layers. The residual strain was ascertained to linearly increase with the increase in a
_(sub.)
by enhancement of the surface-normal lattice spacing of (Ba
_0.5
Sr
_0.5
)TiO
₃
and Pt. Dielectric tunability of the films also linearly increased with the increase in a
_(sub.)
. These results clearly demonstrate that dielectric tunability tailoring of the (Ba
_0.5
Sr
_0.5
)TiO
₃
films can be achieved by using residual thermal strain.