The energy gap of carbon clusters studied by scanning tunneling spectroscopy

Electronic properties of carbon clusters with diameters d between 4 and 1100 إ were studied by scanning tunneling spectroscopy (STS). Large-sized clusters all showed the zero band gap of graphite. A gap opening was observed for clusters with diameters less than about 15 إ. Energy gaps up to 650 meV were measured. The experimental results were modeled using a finite barrier potential for confined electrons, with consideration of the effective mass.