Abstract:
Individual gold nanoparticles exhibit discrete capacitances
of the order of 1 aF, and they can be tethered to a
conductive substrate using a bi-functional monolayer of a suitable
organic molecule. However the conduction, retention and
leakage of charge by such an attached “nanocapacitor” will be
an important issue in any practical application of this concept.
Here we investigate the electrical properties of the particles using
a combination of scanning tunneling spectroscopy and numerical
modeling based on equalizing Wentzel–Kramers–Brillouin style
tunneling currents. Application of the model provides the voltage
division across the structure, and, together, with an estimate of the
capacitance of the particle, provides an indication of likely stored
charge and energy and its decay. The methodology was tested
with I–V data measured for an Au {111} p-xylyldithiol-Au
nanoparticle system in air. About 25 eV can be stored on the
nanoparticles using a charging voltage of 3 V, corresponding
to up to twenty electrons. However, leakage of the charge will
occur by tunneling in approximately 6x10 9 s. Therefore, these
nanocapacitors would discharge completely in any electric circuit
slower than about 1.5 GHz.
