Measurement and Statistical Analysis of Single-Molecule Current–Voltage Characteristics, Transition Voltage Spectroscopy, and Tunneling Barrier Height

Abstract

We report on the measurement and statistical study of thousands of current-voltage characteristics and transition voltage spectra (TVS) of single-molecule junctions with different contact geometries that are rapidly acquired using a new break junction method at room temperature. This capability allows one to obtain current-voltage, conductance voltage, and transition voltage histograms, thus adding a new dimension to the previous conductance histogram analysis at a fixed low-bias voltage for single molecules. This method confirms the low-bias conductance values of alkanedithiols and biphenyldithiol reported in literature. However, at high biases the current shows large nonlinearity and asymmetry, and TVS allows for the determination of a critically important parameter, the tunneling barrier height or energy level alignment between the molecule and the electrodes of single-molecule junctions. The energy level alignment is found to depend on the molecule and also on the contact geometry, revealing the role of contact geometry in both the contact resistance and energy level alignment of a molecular junction. Detailed statistical analysis further reveals that, despite the dependence of the energy level alignment on contact geometry, the variation in single-molecule conductance is primarily due to contact resistance rather than variations in the energy level alignment.

Barrier height distribution and dipolar relaxation in metal-insulator-semiconductor junctions with molecular insulator: Ageing effects

“…19,[35][36][37] Figure 3 (inset) shows the distribution of conductance, G ¼ dJ/dV, values measured in reverse bias (0 V) and forward bias (þ1 V) regimes, for fresh C 12 junctions prepared in nominally identical conditions. The average values and typical distribution over one decade found for G (rev.)…”

“…49 As a consequence, a large dispersion in electrical properties of the corresponding devices is expected and has been observed. 19,[35][36][37] In the particular case of macroscopic a)…”

A quantum chemical study from a molecular transport perspective: ionization and electron attachment energies for species often used to fabricate single-molecule junctions

“…It can be compared to a tunneling barrier, which charge carriers have to overcome to generate a current. Ultraviolet photoelectron spectroscopy (UPS) 1 , thermopower [2][3][4] , and transition voltage spectroscopy (TVS) [5][6][7][8][9][10] represent current methods to estimate the relative alignment of the dominant molecular orbital from experimental data.…”

Suppression of electron–vibron coupling in graphene nanoribbons contacted via a single atom

“…The contacts are typically realized through specific chemistries by using terminal functional groups, for example, thiols for bonding to gold 4,5 . However, these approaches are not necessarily ideal in terms of electrical transparency, mechanical stability and atomic level control over the bonding geometry [5][6][7] .…”