Capacitance of a molecular overlayer on the silicon surface measured by scanning tunneling microscopy

The capacitance of ultrathin cyclopentene overlayers on a $\mathrm{Si}\mathrm{}\left(100\right)-2\mathrm{}\times 1$ surface have been measured using scanning tunneling microscopy (STM). Both tunneling barrier height spectroscopy and tunneling barrier height imaging were used to obtain the values of tip-surface separation, electric field, and the apparent tunneling barrier height of the surface. The apparent tunneling barrier height indicates the magnitude of a local electronic charge on the surface, which corresponds to the capacitance of molecular overlayer. In this study, the capacitance of single molecule adsorption area was found to be $C=1.3\mathrm{}\times {10}^{-20}\mathrm{F},$ which comprises the dipole moment of cyclopentene molecule itself and the charge transfer between the molecule and the surface. A series of STM measurements for determining the capacitance of nanometer-scale structures was then proposed.