摘要：Tin monosulfide (SnS) is a naturally p -type semiconductor with a layered crystal structure, but no reliable n -type SnS has been obtained by conventional aliovalent ion substitution. In this work, carrier polarity conversion to n -type was achieved by isovalent ion substitution for polycrystalline SnS thin films on glass substrates. Substituting Pb2+ for Sn2+ converted the majority carrier from hole to electron, and the free electron density ranged from 1012 to 1015 cm−3 with the largest electron mobility of 7.0 cm2/(Vs). The n -type conduction was confirmed further by the position of the Fermi level ( E F) based on photoemission spectroscopy and electrical characteristics of pn heterojunctions. Density functional theory calculations reveal that the Pb substitution invokes a geometrical size effect that enlarges the interlayer distance and subsequently reduces the formation energies of Sn and Pb interstitials, which results in the electron doping.
