Percolation transition of thermoelectric properties in PbTe thin films

Abstract

Extrema were observed in the film thickness d dependence of various thermoelectric parameters (Seebeck coefficient S, electrical conductivity σ, Hall coefficient RH, charge carrier mobility μ, and power factor P) of epitaxial PbTe/(001) KCl thin films prepared by thermal evaporation in vacuum and protected from oxidation by an EuS layer. We attribute the observed extrema in properties and the high values of μ and P at d≈50 nm to the percolation transition from an island-like to a continuous film and to the self-organization of the islands, which can occur not only in quantum dot superlattices but also in an individual layer.

Self-organization processes in PbTe-Bi2Te3 semiconductor solid solutions and thermoelectric properties

“…Earlier, in a number of IV-VIbased solutions, we detected anomalies of properties in the range 0.5-1.5 mol.% of IA [13][14][15][16][17][18] and interpreted them as a manifestation of percolation type phase transitions occurring under the transition from the impurity discontinuum to the impurity continuum [19]. That is why the first maximum in the V(x) and S(x) dependences can be interpreted as the attainment of the percolation threshold in the impurity subsystem of the crystal.…”

Size effects in p-PbTe nanostructures on polyamide

“…Note that analysing d-dependences for thermoelectric parameters of nanostructures, one should take into consideration the self-organization processes that determine its maxima [11,12,16]. These approaches to explanation of experimental data are vindicated by coincidence of the point extrema in thickness dependences of independently measured Hall RB H B and Seebeck coefficients S (Figs 2 and 3).…”

Some properties of very thin Bi 2 Te 3 layers prepared by laser ablation

“…The improvement of the figure of merit is caused by the fact, that very thin layer present a two dimensional system [1]. Recently, very interesting results were obtained on thin PbTe films prepared by thermal evaporation in vacuum [2] where great improvement of properties was observed for layers of thickness close to 50 nm.Thin Bi 2 Te 3 films were earlier prepared by several methods: sputter deposition [3 -4], co-evaporation of the elements [5], flash evaporation [6-9], molecular beam epitaxy [10,11] and pulsed laser deposition [12]. The pulsed laser technique was found to be suitable for preparation of layers at room temperature with the stoichiometry close to the bulk Bi 2 Te 3 crystal [12].…”

“…A high power pulsed laser radiation (1) is used as an external energy source to vaporise materials of target (5) and to deposit thin films. A set of optical components is used to focus the laser beam to the target surface (2,3). After the laser pulse irradiation the temperature rises very rapidly (10…”