Effects of Surface Band Bending and Scattering on
Thermoelectric Transport in Suspended Bismuth Telluride Nanoplates
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Abstract
A microdevice
was used to measure the in-plane thermoelectric properties
of suspended bismuth telluride nanoplates from 9 to 25 nm thick. The
results reveal a suppressed Seebeck coefficient together with a general
trend of decreasing electrical conductivity and thermal conductivity
with decreasing thickness. While the electrical conductivity of the
nanoplates is still within the range reported for bulk Bi<sub>2</sub>Te<sub>3</sub>, the total thermal conductivity for nanoplates less
than 20 nm thick is well below the reported bulk range. These results
are explained by the presence of surface band bending and diffuse
surface scattering of electrons and phonons in the nanoplates, where
pronounced n-type surface band bending can yield suppressed and even
negative Seebeck coefficient in unintentionally p-type doped nanoplates