Visualizing the Role of Molecular Orbitals in Charge Transport through Individual Diarylethene Isomers

Abstract

Diarylethene molecules are prototype molecular switches with their two isomeric forms exhibiting strikingly different conductance, while maintaining similar length. We employed low-temperature scanning tunneling microscopy (STM) to resolve the energy and the spatial extend of the molecular orbitals of the open and closed isomers when lying on a Au(111) surface. We find an intriguing difference in the extension of the respective HOMOs and a peculiar energy splitting of the formerly degenerate LUMO of the open isomer. We then lift the two isomers with the tip of the STM and measure the current through the individual molecules. By a simple analytical model of the transport, we show that the previously determined orbital characteristics are essential ingredients for the complete understanding of the transport properties. We also succeeded in switching the suspended molecules by the current, while switching the ones which are in direct contact to the surface occurs nonlocally with the help of the electric field of the tip.

Inhomogeneous broadening of the conductance histograms for molecular junctions

“…The techniques mostly rely on some form of metal-electrode breaking, such that a gap is formed of the proper size for bridging by a single molecule. The most widely employed methods are mechanically controllable break junctions [1][2][3] (MCBJ), modified scanning tunneling microscopes [4][5][6][7][8][9][10] (STM) or atomic force microscopes [11,12] (AFM), and bridges formed by electromigration of a nanofabricated metal wire. [13,14] When studies at cryogenic temperatures are required, as is needed to obtain sufficient resolution for resolving the electronic and vibrational structure of a molecule from differential conductance or shot noise measurements, STM and AFM techniques become very elaborate.…”

Electrospray Deposition and Magnetic Properties of Prototypical Molecular Magnets

“…Figure 3b surface with the six lobes corresponding to its outer dpm ligands [61]. At this coverage there are neither preferred adsorption sites nor directional correlations with the herringbone reconstruction of the underlying gold substrate as it is the case for smaller molecules [63,64]. At lower coverage single molecules are found to preferably sitting on elbow sites of the herringbone reconstruction, however they can be easily displaced with the STM tip.…”

Photochromic Diarylethenes Designed for Surface Deposition: From Self‐Assembled Monolayers to Single Molecules

“…(Figure 8g-h) and also performed conductance switching experiments and imaged dI/dV maps. [86] In a subsequent report on the same compound, the authors showed that the switching could be induced either by tunneling electrons or the electric field between the tip and surface. [87]…”