Influence of modulation period on thermoelectric properties for Mg₃Bi₂/Mg/Mg₂Sn multilayer films

Mg₃Bi₂/Mg/Mg₂Sn multilayer films with varying modulation periods were deposited on single crystalline Si substrate by alternating sputtering using high pure metal Mg, Mg₃Bi₂ and Mg₂Sn targets. The chemical and phase composition, surface and cross section image and thermoelectric performance of deposited films were observed, measured and studied. The results revealed that the deposited films were comprised of an evident layered structure containing the metal Mg, the Mg₂Sn and the Mg₃Bi₂ layer. The modulation period affected the carrier transport and thermoelectric properties of multilayer films. Carrier concentration, mobility, electrical conductivity and thermal conductivity of the multilayer films decreased with increasing heterogeneous interface, which severely scatter the carriers and phonon, reducing mobility and thermal conductivity. An increase in the Seebeck coefficient, power factor (PF), and thermoelectric figure of merit (ZT) was obtained by reducing modulation period. At room temperature, the film, which possessed the shortest modulation period of 677 nm, had a maximum ZT value of about 0.26. The carrier and phonon scattering processes were significantly strengthened by the more layer interface, enhancing the deposited film’s thermoelectric figure of merit.