Scanning tunneling current-voltage spectroscopy on poly(p-phenylene vinylene) films: A nanoscale probe for the electronic conduction - art. no. 075311

We have determined the electronic properties of an organic PPV film deposit ed on a p(+)-doped GaAs substrate by scanning tunneling spectroscopy. The n ormalized dynamical conductance curves of the PPV chains show well-defined conduction onsets and/or slope changes corresponding to the electron conduc tion through the LUMO and HOMO levels under forward and reverse bias. A the oretical calculation of the electronic transmission coefficient is used to describe the tunneling current as a function of the sample bias and to unde rstand the electronic properties of the polymer. From the comparison betwee n the calculations and the experimental results we obtain the single partic le energy gap, the Fermi level position and the charge-carrier type.