We have evaluated the thermal conductivity of Si/SiGe superlattice films by theoretical analysis and experiment. In experiments, the ultrahigh vacuum chemical vapor deposition is employed to form the Si/ Si 0.71 Ge 0.29 and Si/ Si 0.8 Ge 0.2 superlattice films. The cross-plane thermal conductivities of these superlattice films are measured based on the 3 method. In the theoretical analysis, the phonon transport in Si/ Si 1−x Ge x superlattice film is explored by solving the phonon Boltzmann transport equation. The dependence of the thermal conductivity of the Si/ Si 1−x Ge x superlattice films on the superlattice period, the ratio of layer thicknesses, and the interface roughness is of interest. The calculations show that when the layer thickness is on the order of one percentage of the mean free path or even thinner, the phonons encounter few intrinsic scatterings and consequently concentrate in the directions having high transmissivities. Nonlinear temperature distributions are observed near the interfaces, arising from the size confinement effect and resulting in a slight increase in the film thermal resistances. The interface resistance due to the interface scattering/ roughness, which is nearly independent of the film thickness, nonetheless dominates the effective thermal conductivity, especially when the superlattice period is small. Finally the experimental measurements agree with the theoretical predictions if the specular fraction associated with the interface is properly taken.

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Bi ∕ Te bilayer thin films were deposited in sequence on oxidized Si wafers by sputtering and converted into Bi2Te3 alloys by thermal annealing. It was found that the Seebeck coefficient rose from −38μV∕Kto−202μV∕K, the resistivity increased slightly from 2.0×10−3to2.3×10−3Ωcm, and the thermal conductivity decreased from 2.56to0.71W∕mK after the Bi∕Te bilayer samples were annealed at 200°C for 24h. Bi2Te3 is the only compound phase identified in the annealed Bi∕Te bilayer samples by x-ray diffraction analysis. The effects of deposition parameters and postannealing condition on the microstructure and the thermoelectric properties of the Bi∕Te bilayer thin films were investigated.

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