Room temperature MBE deposition of Bi₂Te₃ and Sb₂Te₃ thin films with low charge carrier densities

Abstract

Sb2Te3 and Bi2Te3 thin films were grown at room temperature on SiO2 substrates using MBE and were subsequently annealed at 250°C. The films were stoichiometric, polycrystalline, textured, and yielded strikingly low charge carrier densities of about 2.7 × 10(exp 19) cm-3. The in-plane transport properties were measured at room temperature, the thermopower was 130 µVK(exp -1) for Sb2Te3 and -153 µVK(-1) for Bi2Te3 thin films. The small charge carrier densities are explained by a reduced antisite defect density due to the low temperatures to which the thin films were exposed during annealing

Spatially resolved Landau level spectroscopy of the topological Dirac cone of bulk-typeSb2Te3(0001): Potential fluctuations and quasiparticle lifetime

“…Thus, the STS spectrum reveals a significant hole doping in accordance with other STM and ARPES studies [43, 50-52, 54, 55]. The related large carrier density of 2 − 5 · 10 19 cm −3 [58,59] in combination with the surface Dirac cone favorably suppresses tip induced band bending [56]. However, the found E D − E F deviates from a previous ARPES study on the same Sb 2 Te 3 crystal for an unknown reason [49].…”

“…This assumes singly charged defects due to the fact that their charge is not known [54] and cannot be determined by STS. The numbers for E D , n D , and p eff are also displayed in [59], both fits reasonably with the effective p-type doping deduced from our STM images. By comparing area 1 and area 2, one observes that an increased p eff leads to a larger value of E D − E F as expected.…”

Lattice dynamics in Bi2Te3and Sb2TeBessas1, Sergueev2, Wille3 et al. 2012Phys. Rev. B

“…The electronic contribution in heat capacity from activated charge carriers for semiconducting Bi 2 Te 3 above 3 K is insignificant according to Shoemaker et al 53 The presence of defects provides a plausible explanation as defect formation is an important issue in Bi 2 Te 3 . The energy scale for the existence of antisite defects has been recently calculated theoretically 16 and attemps to prove their existence experimentally 54 have been carried out. Activation of trapped charges around these antisite defects could contribute to the measured heat capacity as these charges will cause small lattice distortions.…”

Thermoelectric Characteristics of n-Type Bi₂Te₃ and p-Type Sb₂Te₃ Thin Films Prepared by Co-Evaporation and Annealing for Thermopile Sensor Applications

“…4,5,79,1114) Bi 2 Te 3 and Sb 2 Te 3 are narrow band-gap semiconductors with superior thermoelectric characteristics at room temperature and possess promising potential applications not only for thermopile sensors, but also for micro generators and micro coolers. 5,7,9) While various processing techniques such as evaporation, 11,1318) metalorganic chemical vapor deposition (MOCVD), 19) molecular beam epitaxy (MBE), 12,20,21) sputtering 2125) and electrodeposition 4,5) can be used for thermoelectric thin-film fabrication, evaporation is attractive because it is less expensive process than MOCVD, MBE and sputtering. 17) Evaporation has also an advantage of easy formation of a thermopile device, compared to electrodeposition for which successive formation and removal of seedlayers for electrodeposition of p-type and n-type thin-film legs are required.…”