Efficient Molecular\nRectification in Metal–Molecules–Semimetal\nJunctions

Molecular rectification is expected to be observed in\nmetal–molecule–metal\ntunnel junctions in which the resonance levels responsible for their\ntransport properties are spatially localized asymmetrically with respect\nto the leads. Yet, effects such as electrostatic screening and formation\nof metal induced gap states reduce the magnitude of rectification\nthat can be realized in such junctions. Here we suggest that junctions\nof the form metal–molecule(s)–semimetal mitigate these\ninterfacial effects. We report current rectification in junctions\nbased on the semimetal bismuth (Bi) with high rectification ratios\n(>10<sup>2</sup>) at 1.0 V using alkanethiols, molecules for which\nrectification has never been observed. In addition to the alleviation\nof screening and surface states, the efficient rectification is argued\nto be related to symmetry breaking of the applied bias in these junctions\nbecause of a built-in potential within the Bi lead. The significance\nof this built-in potential and its implications for the future and\nother applications are discussed.