This seed was focused on trying to understand the nature of the interfacial layer formed when pentacene is directly deposited onto silicon, and how this changes when cyclopentene is used as an intermediate buffer layer. These experiments used core-level photoemission to quantitatively identify the coverage, valence-band photoemission to examine the evolution of pi-orbital character in the ultra-thin films, and used Fourier-transform infrared spectroscopy to probe the chemical changes occurring in the film.

Initial results showed a number of interesting features. First, it was possible to definitively identify the types of changes in bonding that occur during the first several monolayers of deposition. Our results showed that pentacene links to the clean Si(001) surface via formation of approximately 8 chemical bonds; this bond formation completely disrupts the molecular pi system, as evidence by well-defined changes in the vibrational spectrum. Measurements of the polarization dependence of the infrared spectrum also showed that the loss of pi-conjugation is also accompanied by changes in molecular shape that lead to a non-planar molecular geometry.