Fig. 5: Thermal transport properties, and zT of P- and N-type films.

a Temperature dependent total thermal conductivity and (b) lattice thermal conductivity versus Te content for P-type Bi0.4Sb1.6Te3+x and N-type Bi2Te3+x films; (c) Room-temperature spectral lattice thermal conductivity (κs) calculated using the Debye–Callaway model. G represents grain boundary scattering, U refers to the Umklapp process, PD refers to the point defect scattering, and D refers to the dislocation scattering, and S refers to the stacking faults scattering. d thermoelectric figure of merit for P-type Bi0.4Sb1.6Te3+x and N-type Bi2Te3+x films in this work.