Investigation of the growth mechanism, structure, and thermoelectric properties of thin PbTe films grown on mica

摘要

The growth mechanisms, structure and thermoelectric properties of thin PbTe films prepared by thermal evaporation in vacuum and subsequent deposition on mica substrates at temperatures T_s = 375, 525 and 635 K were studied. The films were prepared from charge with different electron concentrations (n ≈ 10~(17) and n ≈ 10~(20) cm~(-3)). The film thickness was varied in the range d = 4-500 nm. Electron microscopy study showed that PbTe grows on mica epitaxially in an island like fashion predominantly in the (111) orientation. It is established that in PbTe films there exists a critical thickness at which the transition from electron to hole conductivity with decreasing d is observed. Covering films with a protective layer, lowering the substrate temperature and increasing electron concentration in the charge result in narrowing of the thickness range corresponding to hole conductivity. It is shown that electron concentrations n in the charge and in thick PbTe films grown at the substrate temperature T_s = 525 K differ, the character and magnitude of this difference depending on n in the charge.