Reduction of the contact resistance by doping in pentacene few monolayers thin film transistors and self-assembled nanocrystals

The authors study the contact resistance of gold-pentacene interface by applying the transmission-line method to a few monolayers thick pentacene films in thin film transistor geometry. It was found that tetrafluorotetracyanoquinodimethane $\left({\mathrm{F}}_4\mathrm{TCNQ}\right)$ doping reduces the contact resistance by more than a factor of 20. In addition, a significant improvement of the conductance of pentacene nanocrystals self-assembled on $10\mathrm{nm}$ gap Au nanojunction devices by ${\mathrm{F}}_4\mathrm{TCNQ}$ doping is observed. The result demonstrates the importance of doping on the performance of organic electronic devices from $10\mathrm{nm}$ scale up to $100\mu \mathrm{m}$ scale.