Regensburg 2007 – scientific programme
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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices
SYOE 8: Poster Session SYOE
SYOE 8.14: Poster
Tuesday, March 27, 2007, 18:00–20:00, Poster B
Engineering of the energy level alignment in silicon/organic and silicon/metal heterostructures by methyl-termination of Si(111) — •Ralf Hunger1, Bengt Jäckel1, Taek Lim1, Tetsuya Osaka2, Daisuke Niwa2, Lauren Webb3, Nathan Lewis3, and Wolfram Jaegermann1 — 1Institut für Materialwissenschaften, TU Darmstadt — 2Waseda University, Tokyo — 3CalTech, Pasadena
For optimizing the charge transport across inorganic / organic phase boundaries in hybrid devices, the control over the relative position of the respective electron energy levels is of utmost importance. We have studied the effect of the methyl-termination on the energy level alignment of Si(111)-CH3/ZnPc and Si(111)-CH3/Ag, Cu, and Au interfaces. The methyl-terminated Si(111) surface is an interesting model system as it allows for chemical and electronic surface passivation with 100% organic coverage and a high degree of ordering [Hunger et al., Phys. Rev. B 72, 045317 (2005)].
The interfaces were prepared by stepwise evaporation in vacuum and subsequent characterization by synchrotron photoelectron spectroscopy at BESSY 2. We observed a modification of the energy level alignment for Si / ZnPc and Si / Ag interfaces by the methyl-termination by about +0.3 eV and -0.2 eV, respectively. These modifications can be understood by an interface dipole in case of the silicon/methyl/organic dye contact, and a lowering of the metal work funtion effect for the silicon/methyl/Ag junction.