SCANNING SURFACE HARMONIC MICROSCOPY OF SELF-ASSEMBLED MONOLAYERS ON GOLD

Adsorption of self-assembled monolayers on gold surfaces greatly enhan ces the local probe-induced third-harmonic (TH) generation at microwav e frequency. At a given location the TH signal is, as a function of ga p distance, proportional to the tunneling current. A constant TH signa l image of self-assembled monolayers made from 11-mercaptoundecanol sh ows the same depression pattern with similar resolution as that obtain ed with tunneling microscopy. The tunneling current remains constant a cross the depressions at constant TH signal. However, the TH signal is enhanced on certain protrusions of the monocomponent layers and on ne t-like patterns on the layers made from mixtures of perfluorononanoyl- 2-mercaptoethylamide and 1-mercaptododecane.