Figure 1: Working principle of the device.
This working principle is used to measure the energy barrier at metal/C60 interfaces. (a,b) Scheme of the energetics of the device. EF represents the Fermi energy of the metals. The tunnelling current IE flows when a bias VEB is applied at the emitter/base terminals. When the bias VEB is lower than the energy barrier Δ at the metal/C60 interface, IE flows into the base where it is measured as base current IB. In this case, no current is measured into the C60 (a). When the bias VEB is higher than Δ, part of the tunnelling current IE flows into the C60 and is measured as collector current IC-hot even in the absence of an external voltage directly applied across C60 (VBC=0) (b). (c) Hot electron current IC-hot as a function of the applied bias between emitter and base VEB measured at the collector in a device with a 10-nm-thick Cu base at 245 K. The barrier height is Δ=0.95 V, as obtained by interpolating the linear fit of the growth and the I=0 line.
