Electric Field-Induced Isomerization of Azobenzene by STM

Abstract

The electric field applied between the tip of a scanning tunneling microscope and a metallic surface is shown to induce the reversible trans-cis isomerization of single azobenzene derivatives adsorbed on a Au(111) surface. The investigated molecule is symmetrically equipped with four tert-butyl groups, which decouple the azobenzene core from the metallic surface, facilitating the formation of highly ordered islands. Due to the spatial extension of the electric field, it is possible to switch many molecules within the same island simultaneously.

Spatial periodicity in molecular switching

“…1c-f ), are found after adsorption on Au(111). Note that TBA 6,8,13 and also diM-TBA (4,4 0 -dimethoxy-3,3 0 ,5,5 0 -tetra-tert-butylazobenzene; see Supplementary Information) adopt just one structure, which is similar to structure I (Fig. 1c).…”

“…Switches represent a prototype of such functional molecules because they exhibit characteristic states of different physical/chemical properties, which can be addressed reversibly 3 . Recently, various switching entities have been studied and switching of single molecules on surfaces has been demonstrated [4][5][6][7][8][9][10][11][12][13] . 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.…”

“…Molecular switches located on surfaces have been investigated extensively over recent years, particularly isolated molecules 4,5,12 and two-dimensional (2D) molecular aggregates [6][7][8][9][10][11]13 . These studies have mostly focused on azobenzene derivatives undergoing characteristic trans-cis isomerization triggered by light 7,8 , tunnelling electrons 4,5,13 or an electric field 6 .…”

“…These studies have mostly focused on azobenzene derivatives undergoing characteristic trans-cis isomerization triggered by light 7,8 , tunnelling electrons 4,5,13 or an electric field 6 . In some cases, multiple switching events seem to be influenced by adjacent molecules 9,10 .…”

“…In some cases, multiple switching events seem to be influenced by adjacent molecules 9,10 . The use of bulky tert-butyl side groups has proved to be useful because they weaken the interaction between the central azobenzene core with the substrate while, at the same time, allowing convenient monitoring of the switching event by scanning tunnelling microscopy (STM) 6,8,13 .…”