One potential application of molecular nanotechnology is the integration of molecular electronic function with advanced silicon technology. One step in this process is the tethering of individual molecules at specific locations on silicon surfaces. This paper re-ports the fabrication of arrays of individual organic molecules on H-passivated Si(100) surfaces patterned by UHV STM. Feedback controlled lithography (FCL) is combined with the hydrogen resist nanofabrication technique1 to create templates of individual silicon dan-gling bonds (see Fig.1). Molecules introduced in the gas phase then spontaneously assemble onto these atomic templates. Copper phthalocyanine (Cu(Pc)) and norbornadiene2 molecular arrays have been made by this technique and studied by STM imaging and spectroscopy. Cu(Pc) molecules appear as a four-fold dark depression surrounding a bright central spot in empty states images, whereas in filled states images they are nearly indistinguishable from Si dangling bonds. These experiments are now focussing on measuring and modifying (by STM) intramolecular electronic structure and probing intermolecular interactions, such as quenching molecular rotation3, by adjusting intermo-lecular spacing. Another aspect of this work is the development of a UHV-compatible nanoscale contacting scheme for probing individual molecules and ultimately contacting nanoscale molecular circuits. Initial experiments4 show that planar p-n junctions are compatible with the H-resist/molecular assembly methods while enabling large voltage drops to be applied across nanoscale dimensions.
Fig. 1: Template of Si dangling bonds made by UHV STM hydrogen desorption. Inset shows two of the sites after adsorption of copper phthalocyanine molecules.
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