AVS 50th International Symposium
    Contacts to Organic Materials Topical Conference Monday Sessions
       Session OM-MoA

Paper OM-MoA5
XPS and HRSEM Studies on the Interfaces of Au/CuPc vs. Au/FCuPc

Monday, November 3, 2003, 3:20 pm, Room 318/319

Session: Contacts to Molecules and Molecular Films (II)
Presenter: X. Yu, Rutgers, The State University of New Jersey
Authors: X. Yu, Rutgers, The State University of New Jersey
T.E. Madey, Rutgers, The State University of New Jersey
Correspondent: Click to Email
Ultrathin films of Au have been grown on both copper phthalocyanine (CuN@sub 8@C@sub 32@H@sub 16@, CuPc) and copper hexadecafluorophthalocyanine (CuN@sub 8@C@sub 32@F@sub 16@, FCuPc) samples at room temperature (RT). These are model systems for metal contacts on organic semiconductors. X-ray photoelectron spectroscopy (XPS) measurements, corresponding to various average Au film thicknesses (from 0.3 to 3.0 Å), show that Au deposited on CuPc does not react, but for Au on FCuPc there is evidence for possible charge transfer from Au atoms to the four aromatic rings of FCuPc. Annealing the films at 125°C for one hour enhances charge transfer at the interfaces of Au/FCuPc, while it does not cause any chemical reactions at the interfaces of Au/CuPc. High-resolution field emission scanning electron microscopy (HRSEM) was employed to examine the nucleation and growth of Au (average thicknesses from 5 to 180 Å) on CuPc and FCuPc films at room temperature. Au grows in an island mode on four types of samples CuPc (RT), CuPc (125), FCuPc (RT), and FCuPc (125) in the initial stages of Au deposition (average thicknesses from 5 to 15 Å). The number in the parentheses is the temperature of substrates (in degrees Celsius) during CuPc or FCuPc deposition. Au atoms tend to form bigger clusters with a lower cluster density on CuPc surfaces than on FCuPc surfaces. This may indicate a lower diffusivity for Au on FCuPc than on CuPc, perhaps because of a stronger interaction between Au and FCuPc. These observations support our results from XPS studies. The onset of percolation occurs at a Au thickness of @>=@90Å for Au/CuPc (RT) and Au/CuPc (125), and 90Å for Au/FCuPc (RT) and Au/FCuPc (125). A continuous and hole-free Au film is formed at a thickness of 180Å.