Simulation of thermoelectric properties of bismuth telluride single crystalline films grown on Si and SiO2 surfaces

Self-consistent band-energy-structure calculations of the band-energy struc ture of Bi2Te3 single-crystalline films grown on SiO2 and Si surfaces, with a thickness of about 1 mum, have been carried out in order to simulate the rmopower behaviors. The norm-conserving pseudopotential method within the l ocal-density approach was used. The interface crystalline structure was opt imized using a molecular-dynamics geometry optimization, taking into accoun t the electron-phonon anharmonic interaction. The influence of the Si and S iO2 substrates on the structural, electron, and thermopower parameters of B i2Te3, single crystalline films is studied. From the obtained band-energy p arameters' Fermi energy, thermopower coefficients were calculated for diffe rent types of substrates. A good agreement between theoretical simulations and experimentally obtained data was found. In order to evaluate the role o f the bulk structure, similar measurements have been done for the Bi2Te3 si ngle crystals with appropriate carrier concentrations as well for the Bi2Te 3 crystals covered by Si and SiO2 substrates. The obtained data show the ke y role of intercrystalline interfaces in the observed phenomena. The correl ation between the measured electro-optic coefficients and simulated thermoe lectric parameters indicates the essential role of carrier transfer at the border between the interacting crystalline surfaces.