Enhanced thermoelectric efficiency in Bi₂Te₃ nanoplates and SnSe₂ films.

We present a facile method to improve the thermoelectric efficiency of CVD grown 2D Bi₂Te₃ nanoplates through remediation of unintentional surface doping. The as-grown flakes of Bi₂Te₃ exposed to ambient conditions exhibit relatively small thermopowers. The high surface-to-volume ratio of these thin nanoplates makes them especially sensitive to surface doping, which is a common problem among nanomaterials in general. After surface passivation by deposition of 30nm of Al₂O₃ using ALD, the Seebeck coefficient of these flakes increases by a factor of 5X (from -34 to -169 µV/K). Here, the surface passivation can prevent the degradation of the thermoelectric properties caused by gas adsorption and surface oxidation processes, thus increasing the Bi₂Te₃ Seebeck coefficient.¹

We also report cross-plane thermoelectric measurements of SnSe and SnSe₂ films grown by the modulated element reactant (MER) approach. By performing post-growth annealing at a fixed Se partial pressure, a transition from SnSe-to-SnSe₂ is induced which results in a 16-fold increase (from -38.6 to -631µV/K) in the cross-plane Seebeck coefficient.²

1. Jihan Chen, et. al., Applied Physics Letters 113, 083904 (2018)
2. Jihan Chen, et. al.,Nano Letters, 18.11, 6876 (2018)