Benchmarking break-junction techniques: electric and thermoelectric characterization of naphthalenophanes

Break-junction techniques provide the possibility to study electric and thermoelectric properties of
single-molecule junctions in great detail. These techniques rely on the same principle of controllably
breaking metallic contacts in order to create single-molecule junctions, whilst keeping track of the junc-
tion’s conductance. Here, we compare results from mechanically controllable break junction (MCBJ) and
scanning tunneling microscope (STM) methods, while characterizing conductance properties of the same
novel mechanosensitive para- and meta-connected naphtalenophane compounds. In addition, thermo-
power measurements are carried out for both compounds using the STM break junction (STM-BJ) tech-
nique. For the conductance experiments, the same data processing using a clustering analysis is per-
formed. We obtain to a large extent similar results for both methods, although values of conductance and
stretching lengths for the STM-BJ technique are slightly larger in comparison with the MCBJ. STM-BJ
thermopower experiments show similar Seebeck coefficients for both compounds. An increase in the
Seebeck coefficient is revealed, whilst the conductance decreases, after which it saturates at around
... mehr
10 μV K$^{−1}$ . This phenomenon is studied theoretically using a tight binding model. It shows that changes of
molecule-electrode electronic couplings combined with shifts of the resonance energies explain the cor-
related behavior of conductance and Seebeck coefficient.