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

Abstract

Mg–Si thin films (23 ≤ at.% Si ≤ 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 × 10−4 Pa and the second Group II when reactor was pumped down to pressure higher than 7 × 10−4 Pa. The Mg2Si phase appeared for all as-deposited films of Group I around the stoichiometric composition region (29 ≤ at.% Si ≤ 37) and in the Mg-rich region (at.% Si < 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 ≤ at.% Si ≤ 38) and the Mg2Si structure was achieved after post annealing under air at temperature ≥140 °C. Thermal stability of Mg2Si thin films was investigated by annealing treatments under air. Superficial Mg2Si structural decomposition began at T > 500 °C and layer morphology and structure damaged while annealing temperature increased up to 700 °C. The films’ electrical resistivity, free carrier concentration and mobility as well as Seebeck coefficient were measured and thermoelectric power factors were discussed vs. composition.

The Seebeck Coefficient of Sputter Deposited Metallic Thin Films: The Role of Process Conditions

“…The strong contribution grain-boundary scattering could have on the Seebeck coefficient was also already hinted by other authors [26,40,63]. However, to our knowledge, elaborated experimental studies on the Seebeck coefficient of sputtered thin films, their relation to deposition conditions [64] and proof for the dominant character of the domain size on the Seebeck coefficient of (metallic) thin films [26] remains very limited. Based on the above discussion and in agreement with the latter work of Barber et al [26], we conclude that the microstructural development during film growth can account for the observed variations in the film Seebeck coefficient as function of the layer thickness.…”

Impacts of Cu-Doping and Mg-Deficiency on Mg2Sn Thin Films Thermoelectric Properties

“…As shown in Table I, many works have focused on bulk materials, while development of thin films with an optimized ZT value is essential to reduce the size of current thermoelectric devices in order to use them in miniaturized applications such as microelectro-mechanical systems 22 and internet of things. 23 Different methods have been suggested for producing thermoelectric thin films, such as flash evaporation, 24 pulsed laser deposition, 25,26 electrochemical deposition, 27 metal organic chemical vapor deposition, 28 sputtering, [29][30][31][32] and molecular beam epitaxy. 33 Among these techniques, magnetron sputtering has many advantages, such as a good reproducibility, an easy way to control the film composition and homogeneity, environmentally friendly, and so on.…”