2-DIMENSIONAL LIQUID-PHASE AND THE PX-ROOT-3-PHASE OF ALKANETHIOL SELF-ASSEMBLED MONOLAYERS ON AU(111)

Alkanethiols CH3(CH2)(n)-1SH (C-n n = 4, 6, 8, 10) were self-assembled from ethanolic solutions onto a single-crystal Au(111) surface and characterized using an ultrahigh vacuum scanning tunneling microscope (STM). Short-chain homologues (C-4 and C-6) exhibited a two-dimensional (2-D) liquid phase at room temperature. Facile mass transport of surface gold atoms was observed in the presence of the liquid phase. The short-chain homologues exhibited slow desorption of surface thiolate which led to the nucleation and growth of ordered domains having a unit cell of p x root 3 (8 less than or equal to p less than or equal to 10). No 2-D liquid phase was observed for longer chain homologues (C-8 and C-10).