Spatial periodicity in molecular switching

Abstract

The ultimate miniaturization of future devices will require the use of functional molecules at the nanoscale and their integration into larger architectures. Switches represent a prototype of such functional molecules because they exhibit characteristic states of different physical/chemical properties, which can be addressed reversibly. Recently, various switching entities have been studied and switching of single molecules on surfaces has been demonstrated. However, for functional molecules to be used in a future device, it will be necessary to selectively address individual molecules, preferentially in an ordered pattern. Here, we show that azobenzene derivatives in the trans form, adsorbed in a homogeneous two-dimensional layer, can be collectively switched with spatial selectivity, thus forming a periodic pattern of cis isomers. We find that the probability of a molecule switching is not equally distributed, but is strongly dependent on both the surrounding molecules and the supporting surface, which precisely determine the switching capability of each individual molecule. Consequently, exactly the same lattices of cis isomers are created in repeated erasing and re-switching cycles. Our results demonstrate a conceptually new approach to spatially addressing single functional molecules

Quantum Chemical Investigation of Thermal Cis-to-Trans Isomerization of Azobenzene Derivatives: Substituent Effects, Solvent Effects, and Comparison to Experimental Data

“…30 Further, derivatives were considered in which two tert-butyl groups of TBA were replaced by -COOH groups, i.e., 3,5-ditert-butyl-3,5′-dicarboxyl-AB (DBDCA), 31 or in which two of the four tert-butyl groups were rearranged, 2,2′,5,5′-tetra-tertbutyl-AB (TBA′)ssee the Supporting Information for details.…”

Observing single-atom diffusion at a molecule-metal interface

“…The study of such systems gives detailed insight into fundamental processes that take place at an organic-inorganic interface. For an in-depth understanding, it is advantageous to use a scanning tunneling microscope (STM) for imaging because it provides information about the local environment of each individual molecule, which is important since the molecular properties might differ locallydue to defects, step edges, or different areas of a surface reconstruction [4,5]. For instance, individual C 60 molecules were found to change between dark and bright appearances in STM images, caused by the diffusion of surface [6] or bulk [7] vacancies, charge transfer between molecule and surface [8], or adsorption on small metal islands [9].…”

Charge-Transfer-Induced Isomerization of DCNQI on Cu(100)

“…[2][3] With a few exceptions, [4][5][6][7] most of these studies have focused on azobenzene derivatives on metal surfaces, where isomerization can be induced by light, [8][9] thermal energy, 9 and the tunneling current [10][11] or the electric field 12 from an STM tip. However, it has been shown that different substrates, 13 different surface orientations, 13 or even different areas of the same surface [14][15] can suppress the isomerization for the same molecules. In a recent report the surface has been suggested to lower the energy barrier for isomerization, but no specific mechanism could be identified.…”