Origin of the asymmetric electronic structures between Au/pentacene and pentacene/Au interfaces
Ihm, Kyuwook; Heo, Hye-Eun; Kang, Tai-Hee; Kim, Ki Jeong; Kim, Bongsoo; Chung, Sukmin Republic of Korea
Au film formed on the pentacene surface shows abnormal electronic structures than crystal Au film, such as low workfunction and density of states near the Fermi level crucial for ohmic contact and current flowing because holes flow along near the Fermi surface in the solid.
These abnormal electronic structures of Au film on the pentacene surface are found to result from the concurrently observed unexpected carbon species and irregular morphology of Au film induced by the relaxation of the accumulated stress with different strength of the grains formed at elevated temperature during Au deposition. We have investigated the source of the carbon species by synchrotron radiation spectroscopy and calculation based on Fick's second law. The microscopic analysis shows that the Au film at various thickness has different morphology resulting from different grain size and relaxation of the intergranular stress during cooling down after Au deposition. TEM (transmission electron microscopy) image show that the relaxation of Au film induces the deformation of the Au grains as well as of the pentacene film beneath the Au grain.