Thin films of lead telluride (PbTe) of different thicknesses ranging between 500 ? to 2500 ? have been prepared by thermal evaporation technique onto precleaned amorphous glass substrates at room temperature. Selected virgin samples were annealed at temperature 523 K for 60 min. in vacuum (≈10-5 torr). The X-ray diffraction analysis confirmed that these annealed films are polycrystalline corresponding to the rock salt (NaCl) FCC structure. From the XRD profiles, the grain size, dislocation density, micro strain and lattice constants were calculated. Resistivity of the virgin and annealed samples was measured by four-probe technique as a function of thickness and temperature. The resistivity was measured in the temperature range of 303 K to 473 K. It was observed that for virgin samples the resistivity decreases with increasing film thickness. It shows the NTC behavior of resistivity. For the annealed PbTe films the resistivity shows dramatic change resulting in oscillatory behavior with increasing film thickness Thermoelectric power has been measured by the integral method in the same temperature range and found to be positive indicating that the samples are p-type semiconducting materials. The existence of oscillations in the thermoelectric properties for both the virgin and annealed samples is attributed to quantum size effects.
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