Diodelike Current-Voltage Curves for a Single Molecule—Tunneling Spectroscopy with Submolecular Resolution of an Alkylated, pcri-Condensed Hexabenzocoronene

摘要

The spcctroscopy of single molecules m a defined environment is of relevance not only as a tool in future molecular electronics. A single molecule dispersed amongst manv others in an amorphous matrix ear. be selected by laser speetroscopy on account of its specific surroundings. Single molecule detection is achieved by optical spectroscope in an extremely small sample volume of a highly diluted substance. In the nearfield optical microscope this volume can be as small as 100 nm~3. which is still sufficient for a satisfactory distinction from the background. These methods do. however, not allow for a spatial localization of the molecule. One method that circumvents this shortcoming is the local excitation of luminescence with the help of a scanning tunneling microscope. Another method is tunneling spcc-troseopy of single molecules. At submolecuiar resolution this technique oilers a way to chemically identify individual molecular moieties. It consists of immobilizing the molecules on a solid surface,imaging them by scanning tunneling microscopy (STM). and then performing tunneling spectroscopy (STS) at a specific location. While scanning tunneling microscopv of molecules has evolved into a precise and widespread method. feu reliable results have been published for spatially resolved tunneling spectroscopy.