Temperature-Dependent Electron Transport in Single Terphenyldithiol Molecules.

Analyzing the electronic properties of individual terphenyldithiol (TPT) molecules in a temperature range of 30-300 K using cryogenic mechanically controllable break junctions, we observe an unexpected change of the transport mechanism with temperature for this linear and symmetric aromatic molecule. Whereas the work function (∼3.8 eV) and molecular energy level (∼0.8 to ∼1 eV depending on the analysis of the data) of TPT are temperature-independent, elastic tunneling dominates charge transport at low temperatures, whereby an inelastic transport (via hopping) sets in at about 100 K. The molecular level of TPT lies around 1 eV and is temperature-independent. This unusual temperature dependence agrees with recent predictions for other short molecules using density-functional-based transport studies as well as experimental observations obtained for similar relatively short rodlike molecules.