Thermoelectric properties of Bi_2Te_3 based thin films fabricated by pulsed laser deposition

摘要

Bi_Te_3-based thin films were fabricated on glass substrates by the pulsed laser deposition (PLD) method. The vapor pressures of Bi and Te are significantly different, so controlling the stoichiometric composition is difficult when using conventional physical vapor deposition techniques, and the thermoelectric properties of Bi_2Te_3 films are sensitive to the film composition. PLD is a promising technique for the fabrication of telluride-based films such as Bi_2Te_3 due to its superior capability for controlling the film composition. Another advantage of PLD is the flexibility that it allows in terms of atmosphere in the reaction chamber; high concentrations of gases such as oxygen or argon can be introduced. We have measured various compositions of Bi_2Te_3-based films, and have identified the optimal compositions for both n-type and p-type material. The thermal conductivities of these Bi_2Te_3 films were evaluated by an exact measuring system, and the results were twice as low as those of conventional bulk materials. These results suggest that PLD has significant advantages for the deposition of in-plane Bi_2Te_3-based thin films.