Thermoelectric properties of β-(Cu,Mn)2Se films with high (111) preferred orientation

Abstract

Mn-doped β-Cu2Se films were prepared on a single-crystalline Si substrate with an insulating SiO2 layer using a sintered Cu–Se compound target by magnetron sputtering. The phase composition, microstructure and thermoelectric properties of deposited films were studied. The results show that the films are composed of only single β-Cu2Se phase with highly (111) referred orientation. Mn replaces Cu atom in β-Cu2Se lattice and β-(Cu,Mn)2Se solid solution forms. In the deposited β-Cu2Se films doping Mn, the atomic ratio ([Cu]+[Mn])/[Se] of Cu + Mn to Se content exceeds 2.0. The deposited β-(Cu,Mn)2Se films possess p-type conductivity characteristics. The carrier concentration decreases and the carrier mobility increases with increasing Mn content, respectively. The resistivity and Seebeck coefficient of the deposited films increase with increasing Mn content. The film with 1.94 at.% Mn possesses the highest power factor in the range of 100–400 °C and its figure of merit (ZT) reaches 0.85 at room temperature. The thermoelectric properties of the β-Cu2Se films are able to be improved by doping an appropriate amount of Mn and obtaining highly (111) preferred orientation.