Influence of atomic ratio of Mg to Sn on thermoelectric properties of Mg2Sn films

The influence of Mg/Sn ratio of on the thermoelectric properties of Mg-Sn films was deeply studied through preparing a series of Mg2Sn films with different Mg and Sn atomic ratios on SiO2/Si substrate. The results showed that the phase structure of the deposited Mg2Sn films varied from a metastable orthogonal phase to a mixture of orthogonal and cubic phase, and then to a highly symmetric cubic phase with increasing [Mg]/[Sn]. Meanwhile, with increasing [Mg]/[Sn], the carrier concentration and electrical conductivity of the deposited films first decreased and then increased, while the carrier mobility and Seebeck coefficient varied in an opposite trend. The cubic Mg2Sn phase film with [Mg]/[Sn] = 1.94 has the highest Seebeck coefficient and appropriate electrical conductivity, reaching the highest power factor of 3.10 mu W cm(-1) K-2 at 235 degrees C and figure of merit of 0.059 at 125 degrees C.