Electrical properties of unsubstituted/fluorine-substituted phthalocyanine interface investigated by Kelvin probe method

The effect of the substituent group attached to the zinc phthalocyanine (ZnPc) on the surface potential was investigated by Kelvin probe method. Compared with unsubstituted ZnPc deposited on a metal electrode, negative shift of the surface potential was observed for fluorine-substituted ZnPc (ZnPcF16). Since the π-electrons of Pc ring are strongly attracted to the fluorine atoms, the Fermi-level of the Pc molecule lowers with attaching electron-acceptor group. Electron displacement at the interface between ZnPc and ZnPcF16 layer was also confirmed by the surface potential measurement. It is found that excess electrons were transferred from ZnPc to ZnPcF16, and these phenomena were successfully interpreted using molecular orbital calculations