Strain Relaxation in Atomic Flat SrRu$_{1-{\rm x}}$ O$_{3}$ /SrTiO$_{3}$ Layers Grown by Off-Axis RF-Sputtering

Strain-relaxed atomically flat SrRu
$_{1-{\rm x}}$
O
$_{3}$
layers can be grown on SrTiO
$_{3}$
substrate by a standard off-axis RF sputtering technique without using buffer layers. High RF power generated a high concentration of Ru vacancies proportional to the enlarged unit cell volume. The strong interface strain is relaxed by nano-crystal-defects induced by the large Ru vacancies and thin amorphous layer sitting in between film-substrate interface. Because of the structural defects and large unit cell expansion, the
$T_{C}$
is lowered to 110–137 K as compared to bulk value of 161 K. Strong uniaxial anisotropy along [001] direction indicates that the intrinsic bulk SrRuO
$_{3}$
anisotropy dominating over the lattice expansion induced cubic anisotropy.