ICT2014 Abstracts

Bismuth, one of few elemental semimetals, played a paramount role in the history of metal physics as well as in the early stage of thermoelectric research.  As a thermoelectric material, the intrinsic overlap between L-conduction band and T-valence band prevents it from having a competitive thermoelectric figure of merit.  Yet, here we shed new light on this classic semimetal through the study of a new doping impurity: Indium.  Seemingly, this group III element is supposed to have almost no influences on the electronic properties of bismuth, as it possesses the same number of outermost electrons as bismuth.  We show that due to its unusual influence on the electronic structure of bismuth, indium actually behaves as an p-type dopant in bismuth.  Based upon this unusual effect, a novel doping mechanism is proposed which may open a new way to doping studies of thermoelectric materials and even general semiconductors.  Our doping model also provides a new perspective on behavior of tin in bismuth, which has been believed to be a simple monovalent acceptor in bismuth for the past 40 years.  We report transport properties of indium doped bismuth samples, which additionally reveal that indium introduces neutral impurity scattering in bismuth.  As a result, an enhancement of the Seebeck coefficient is achieved, which leads to an improvement of the figure of merit above 160K.