Unsupervised feature recognition in single-molecule break junction data

Abstract

Single-molecule break junction measurements deliver a huge number of conductance vs. electrode separation traces. Along such measurements the target molecules may bind to the electrodes in different geometries, and the evolution and rupture of the single-molecule junction may also follow distinct trajectories. The unraveling of the various typical trace classes is a prerequisite of the proper physical interpretation of the data. Here we exploit the efficient feature recognition properties of neural networks to automatically find the relevant trace classes. To eliminate the need for manually labeled training data we apply a combined method, which automatically selects training traces according to the extreme values of principal component projections or some auxiliary measured quantities, and then the network captures the features of these characteristic traces, and generalizes its inference to the entire dataset. The use of a simple neural network structure also enables a direct insight to the decision making mechanism. We demonstrate that this combined machine learning method is efficient in the unsupervised recognition of unobvious, but highly relevant trace classes within low and room temperature gold-4,4' bipyridine-gold single molecule break junction data. arXiv:2001.03006v1 [cond-mat.mes-hall] 9 Jan 2020

A review of oligo(arylene ethynylene) derivatives in molecular junctions

“…Many of these methods were pioneered using datasets collected for OAE derivatives. 69,146,167,178,[252][253][254][255][256] The utility of these techniques is exemplified by a study of porphyrin-centred OAE3s by El Abbassi et al, who used a clustering algorithm in conjunction with a range of model systems to assign classes of conductance trace to different junction geometries (Fig. 41).…”

Voltage-Controlled Binary Conductance Switching in Gold–4,4′-Bipyridine–Gold Single-Molecule Nanowires

“…Note that this number is partly related to the low molecular pick-up rate in the low-temperature measurements. 25 Out of these stable molecular contacts ≈5% matched the displacement range, where the voltage dependent bistable switching was observable. These 35 independent traces are used to investigate the voltage dependence of the bistable switching in Figures 4 b–j.…”

“…Note that the sub-Ångstrom displacement interval of the conductance hysteresis is almost an order of magnitude narrower than the ≈2 Å average displacement between the centers of the HighG and LowG conductance plateaus on the two-dimensional conductance–displacement histograms. 6 , 25 …”

Single‐Molecule Doping: Conductance Changed By Transition Metal Centers in Salen Molecules

“…The pronounced tilt of the plateaus is a common feature of junctions with molecules that are longer than 2 nm. [24] The length of the conductance plateaus is in the range of 1 nm for both Fe 3+ and Mn 3+ , while the length is shorter (approximately 7 Å) for Co 3+ . Here, we use the full set of recorded plateaus without data selection.…”