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

Abstract

Thin layers of Bi 2 Te 3 60 nm thickness were prepared by laser ablation in vacuum using KrF excimer laser. The energy of laser varied from 300 to 680 mJ and the laser energy density from 2 to 10 J cm -2 . The substrate temperature varied for different depositions in the interval of 20 -500 °C. The influence of preparation conditions on Hall mobility, concentration of charge carriers and conductivity at room temperature is presented. Information about morphology and composition of prepared layers is given.Introduction Very thin layers of thermoelectric materials are potential candidates for many applications because of the expected improvement of their figure of merit in comparison with the bulk materials. 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]. In this paper, we present preliminary measurements of such properties as conductivity, concentration of charge carriers, Hall mobility and stoichiometry of Bi 2 Te 3 layers prepared by laser ablation. In our experiments, we examine the influence of the substrate temperature and the laser energy density on the target during deposition on the above mentioned properties. The configuration of the sample-target is fixed in all experiments.

Tailoring bismuth telluride nanostructures using a scalable sintering process and their thermoelectric properties

“…As can be seen from Table 1, the compositions of the as-prepared sample and sample sintered at 573 K show the Bi 2 Te 3 phase, as it is highly stable at low temperature, 19 whereas a tellurium deficiency was observed in the samples sintered at high temperature (>573 K), and thereby the BiTe phase was formed. 19,20 The tellurium deficiency is probably caused by evaporation, as tellurium is lighter and more volatile than Bi. 21,22 Fig.…”