Face-on orientation of spin ladders in La5Ca9Cu24O41 films deposited by radio-frequency magnetron sputtering on heated SiO2 and Si substrates

Spin-ladder cuprates such as La5Ca9Cu24O41 are promising materials for advanced thermal management applications owing to their highly anisotropic and dynamically controllable thermal conductivity originating from spin ladders. Therefore, the orientation control of spin ladders is required in film fabrication methods that are extensively used in device engineering, such as sputtering. We found that La5Ca9Cu24O41 films with a columnar structure and the face-on orientation of spin ladders are formed on heated SiO2 (glass) and Si substrates via radio-frequency magnetron sputtering. The structural properties of the films were investigated, and the film formation mechanism was discussed. Our film fabrication method can pave the way for the development of new thermal management devices, such as active heat spreaders.