Scanning Tunneling Microscopy Studies of Potassium-Doped Picene Films on Au(111) Surface

Potassium-doped picene films grown on an Au(111) surface have been investigated using low-temperature scanning tunneling microscopy. The evolution of both the morphologies and the electronic properties of the pristine and doped picene films have been carefully studied. With the increase of the K doping ratio, several novel ordered structures sequentially appear on the KxPicene (x = 0-4) film. Meanwhile, owing to the increase of charge transferring from K atoms to picene molecules, the lowest unoccupied molecular orbital state of the films is observed to shift toward the Fermi level. In particular, for K3.4Picene, this state splits into an upper unoccupied part and a lower occupied one when saddling the Fermi level. This may imply the presence of the electronic correlation effect.