K. Pichler et al., CHARGE INJECTION, ELECTRIC-FIELD MODULATION AND SPECTROSCOPY OF CHARGED STATES OF FULLERENE IN METAL-INSULATOR-SEMICONDUCTOR DEVICES, Synthetic metals, 56(2-3), 1993, pp. 3229-3234
we have studied Metal-Insulator-Semiconductor (MIS) devices with fulle
rene as the active semiconductor. We have made impedance analysis meas
urements on these devices and we use these to characterise electrical
transport in fullerene and the interfaces with insulators and metals.
We have measured the modulation of the optical transmission through th
e devices with gate voltage. We see a strong field-dependent modulatio
n of the dipole-allowed transitions. We observe also optical transitio
ns due to charges injected into the fullerene layer when we use C60/C7
0 mixtures. With pure C60 we see features related to charge injection
only when the devices are exposed to illumination above the band gap.
The positions of these charge-induced optical features do not match th
ose observed following chemical doping. The optical characteristics of
the pure C60 and the C70/C60 MIS devices are consistent with the impe
dance analysis.