Towards single molecule switches

Abstract

The concept of using single molecules as key building blocks for logic gates, diodes and transistors to perform basic functions of digital electronic devices at the molecular scale has been explored over the past decades. However, in addition to mimicking the basic functions of current silicon devices, molecules often possess unique properties that have no parallel in conventional materials and promise new hybrid devices with novel functions that cannot be achieved with equivalent solid-state devices. The most appealing example is the molecular switch. Over the past decade, molecular switches on surfaces have been intensely investigated. A variety of external stimuli such as light, electric field, temperature, tunneling electrons and even chemical stimulus have been used to activate these molecular switches between bistable or even multiple states by manipulating molecular conformations, dipole orientations, spin states, charge states and even chemical bond formation. The switching event can occur either on surfaces or in break junctions. The aim of this review is to highlight recent advances in molecular switches triggered by various external stimuli, as investigated by low-temperature scanning tunneling microscopy (LT-STM) and the break junction technique. We begin by presenting the molecular switches triggered by various external stimuli that do not provide single molecule selectivity, referred to as non-selective switching. Special focus is then given to selective single molecule switching realized using the LT-STM tip on surfaces. Single molecule switches operated by different mechanisms are reviewed and discussed. Finally, molecular switches embedded in self-assembled monolayers (SAMs) and single molecule junctions are addressed.

Effect of Ring Strain on the Charge Transport of a Robust Norbornadiene–Quadricyclane-Based Molecular Photoswitch

“…3,11 There are several examples of photoswitching molecules. From a charge transport perspective diarylethenes 12−15 and azobenzenes 5,16,17 have been the two major molecular platforms rigorously studied through various experimental approaches in the past decade.…”

Surface strain mediated dipole alignment of ClAlPc on Au(111)

“…26,27 Reversible molecular switching (i.e., dipole-up versus dipole-down orientation) has been realized in monolayer ClAlPc, VOPc on graphite, 28,29 VOPc in hydrogen-bonded networks on graphite, 30 and SnPc on Cu(111), 31 which might fuel ultrahigh density information storage eventually. 32 To further expand their applications in molecular nanodevice, it is necessary to develop novel interfacial engineering techniques to manipulate the molecular dipoles on a solid surface. In this letter, the strain mediated dipole alignment of nonplanar ClAlPc on the tensile-strained Au(111)/mica and the strain-released single crystal Au(111) was investigated in situ by low-temperature scanning tunneling microscopy (LT-STM).…”

Designing a molecular magnetic button based on 4d and 5d transition-metal phthalocyanines

“…For this purpose the ability to control the magnetization of the system and switch it from one state to the other is also required. Several switching mechanisms have been demonstrated for metalorganic molecules adsorbed on surfaces 5 . A modification of the oxidation state of a molecule’s metal center, e.g.…”