Influence of Sputtering Parameters on Structural, Electrical and Thermoelectric Properties of Mg–Si Coatings

Mg&ndash
Si thin films (23 &le
at.% Si &le
43) were deposited by co-sputtering of Mg and Si targets in an argon atmosphere. Two groups of samples were prepared with respect to sputtering parameters. The first Group I was synthesized while residual pressure in the reactor was lower than 7 &times
10&minus
4 Pa and the second Group II when reactor was pumped down to pressure higher than 7 &times
4 Pa. The Mg2Si phase appeared for all as-deposited films of Group I around the stoichiometric composition region (29 &le
37) and in the Mg-rich region (at.% Si &lt
29) the Mg2Si and Mg phases coexisted. An amorphous structure was obtained for all as-deposited films of Group II no matter their composition (34 &le
38) and the Mg2Si structure was achieved after post annealing under air at temperature &ge
140 &deg
C. Thermal stability of Mg2Si thin films was investigated by annealing treatments under air. Superficial Mg2Si structural decomposition began at T &gt
500 &deg
C and layer morphology and structure damaged while annealing temperature increased up to 700 &deg
C. The films&rsquo
electrical resistivity, free carrier concentration and mobility as well as Seebeck coefficient were measured and thermoelectric power factors were discussed vs. composition.