Electronic structure, diffusion, and p-doping at the Au/F16CuPc interface

Interfaces formed by evaporating Au on copper hexadecafluorophthalocyanine $({\mathrm{F}}_{16}\mathrm{CuPc)}$ and ${\mathrm{F}}_{16}\mathrm{CuPc}$ on Au are studied via ultraviolet photoemission spectroscopy and x-ray photoemission spectroscopy. The energy position of the molecular levels is found to depend on the deposition sequence. The Au-on-${\mathrm{F}}_{16}\mathrm{CuPc}$ interface exhibits a lower hole injection barrier than the ${\mathrm{F}}_{16}\mathrm{CuPc-on-Au}$ interface. This behavior is attributed to the diffusion of Au into the organic matrix at the Au-on-top interface, in which they behave as acceptors. Band bending consistent with p doping, i.e., upward away from the metal interface, is observed in Au-doped ${\mathrm{F}}_{16}\mathrm{CuPc}$ films. Current–voltage measurements on Au/${\mathrm{F}}_{16}\mathrm{CuPc/Au}$ sandwich structures show a higher electron injection barrier at the top Au electrode contact than at the bottom electrode contact, also consistent with p-type doping ${\mathrm{F}}_{16}\mathrm{CuPc}$ by Au.