Scanning tunneling microscopy characterization of aromatic molecules stabilized by a buffer layer of alkane derivatives

Using lamellae of 1-octadecanol and stearic acid as a buffer layer, aromatic molecules such as copper phthalocyanine (CuPc) and nitrobenzene were immobilized on the surface of highly oriented pyrolytic graphite (HOPG), and been characterized by scanning tunneling microscopy (STM). These molecules crystallized in two dimensions on top of the monolayer of alkane derivatives, and high-resolution images of these molecules were obtained. An additional advantage is that the buffer layer underneath does not change the electronic properties of the immobilized molecules. The mechanism of the immobilization of the buffer layer is considered to be the cutting down of charge transfer between the aromatic molecules and graphite. These results proved that this strategy could be used as a general method to immobilize organic species on a substrate surface.