Self-Assembly and Photomechanical Switching of an Azobenzene Derivative on GaAs(110): Scanning Tunneling Microscopy Study

Self-assembly and light-induced mechanical switching of azobenzene derivatives deposited on GaAs(110) were explored at the single molecule level using scanning tunneling microscopy (STM). 3,3′,5,5′-Tetra- tert -butylazobenzene (TTB-AB) molecules in the trans isomer configuration were found to form well-ordered islands on GaAs(110). After exposure to ultraviolet (UV) light, the TTB-AB molecules exhibited conformational changes attributed to trans to cis photoisomerization. Photoisomerization of TTB-AB/GaAs is observed to occur preferentially in one-dimensional (1D) stripes. This 1D cascade behavior differs significantly from optically induced switching behavior observed when TTB-AB molecules are placed on a gold surface.