Preparation of CaMgSi and Ca 7 Mg 7.25 Si 14 single phase films and their thermoelectric properties

Ca-Mg-Si films were firstly prepared on (001)Al 2 O 3 substrates by RF-magnetron sputtering method from Mg disc target together with Ca and Si chips. The composition of the deposited films was controlled by adjusting deposition temperature and Ca/Si area ratio of Ca and Si chips on Mg disk target. Ca 0.32 Mg 0.33 Si 0.35 film deposited at 610 K consisted of a single phase of CaMgSi and this CaMgSi phase was stable after heat treated at 770 K under an atmospheric Ar with 5% -H 2 . As-deposited film shows the semiconductor behavior and have a power factor of 50 µW/(mK 2 ) at 670 K, while annealed one showed the metallic behavior and its power factor down below 10 µW/(mK 2 ) at 320-770 K. On the other hand, Ca 0.27 Mg 0. 51 Si 0.2 film deposited at 590 K showed no obvious crystalline phase but became single phase of Ca 7 Mg 7.25 Si 14 after heat treatment at 770 K under an atmospheric Ar with 5% -H 2 . As deposited film had a large power factor of 100 µW/(mK 2 ) at 670 K. However, power factor decreased below 1 µW/(mK 2 ) at 320-770K after the heat treatment at 770 K under an atmospheric Ar with 5% -H 2 .