Transport properties ofBi(Te)-PbTe thin films composites

A. Jacquot¹, O.Boffoué², M. Dinescu³, B. Lenoir¹, A.Dauscher¹

¹Laboratoirede Physique des Matériaux, UMR CNRS-INPL-UHP 7556, Ecole NationaleSupérieure des Mines de Nancy, Parc de Saurupt, 54042 Nancy, France

²Laboratoire dePédologie et Géologie Appliquée, Université deCocody,

Côte d'Ivoire

³NILPRP,P.O. Box MG-16, RO-76900, Bucharest, România

Low dimensional systems based on lead telluride (PbTe) haveattracted much interest in the field of thermoelectricity. For theirintegration in potential low cost microdevices, high quality films must beachieved on silicon substrates and they have to support numerous temperaturecycles. This is a challenging task since both the differences in lattice parametersand thermal expansion coefficients are important. To overcome the bothunderlined drawbacks, the idea was to use composite materials.

PbTe reference thin films have been prepared under vacuum onto glasssubstrates at 150°C by pulsed laser deposition (PLD). PbTe-Bi and PbTe-Tethin films composites containing nano-inclusions of Bi or Te, respectively,were synthesised under similar conditions by PLD by the way of makingalternative deposit of the components..

The transport properties (electrical resistivity, thermoelectricpower) of the thin films have been measured between 300-80 K, and theirstability towards temperature cycling tested. Strong influence of both apost-annealing treatment and nano-inclusions nature has been observed. Thethermoelectric results have been correlated to changes in film morphology andmicrostructure. PbTe-Bi composites exhibit an excellent compromise betweenthermoelectric performance and thermal stability during temperature cycling.PLD allows making good quality PbTe deposits at much lower temperature than anyother deposition technique. It becomes so perfectly suited to the deposition ofBi that must be performed at low temperature owing to its low melting point.