Abstract
We report on an experimental analysis of the charge transport through sulfur-free photochromic molecular junctions. The conductance of individual molecules contacted with gold electrodes and the current–voltage characteristics of these junctions are measured in a mechanically controlled break-junction system at room temperature and in liquid environment. We compare the transport properties of a series of molecules, labeled TSC, MN, and 4Py, with the same switching core but varying side-arms and end-groups designed for providing the mechanical and electrical contact to the gold electrodes. We perform a detailed analysis of the transport properties of TSC in its open and closed states. We find rather broad distributions of conductance values in both states. The analysis, based on the assumption that the current is carried by a single dominating molecular orbital, reveals distinct differences between both states. We discuss the appearance of diode-like behavior for the particular species 4Py that features end-groups, which preferentially couple to the metal electrode by physisorption. We show that the energetic position of the molecular orbital varies as a function of the transmission. Finally, we show for the species MN that the use of two cyano end-groups on each side considerably enhances the coupling strength compared to the typical behavior of a single cyano group.
Highlights
Charge transport in single-molecule devices is actively investigated with the aim to realize functional electronic circuits [1,2,3,4], such as switches [5], transistors [4,6] or storage devices [7].Novel physical phenomena arise when the junctions are exposed to control schemes including electrochemical or electric-field gating [8,9,10], mechanical stretching [11,12,13], magneticBeilstein J
We investigate charge transport through the species labeled TSC, 4Py and MN, shown in Figure 1c, contacted by adjustable Au electrodes (Figure 1a) in a mechanically controlled break-junctions (MCBJs) system operating at room temperature in a liquid environment [33,35,36]
We have investigated charge-transport characteristics of photochromic molecules using the MCBJ technique in a liquid environment at room temperature
Summary
Charge transport in single-molecule devices is actively investigated with the aim to realize functional electronic circuits [1,2,3,4], such as switches [5], transistors [4,6] or storage devices [7].Novel physical phenomena arise when the junctions are exposed to control schemes including electrochemical or electric-field gating [8,9,10], mechanical stretching [11,12,13], magneticBeilstein J. For the molecular solutions we calculate conductance histograms from ≈100 stretching and relaxing traces, and we find rather weak features in both forms (see Supporting Information File 1) as usual for room-temperature measurements in solution [26,35,36,38,39].
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