Paper SS-FrM8
Monolayer-induced Electronic Structure of Crystalline Semiconductor Surfaces

Friday, November 1, 2013, 10:40 am, Room 201 A

Directly grafted organic monolayers on Si and Ge surfaces offer an interesting opportunity to explore aspects of surface passivation and control of electrical properties, namely, molecular gating, of semiconductor surfaces. We report our study of the interfacial electronic structures of n-, and p-type of Si(111), Si(100) and Ge(111) surfaces that have been chemically modified with various organic monolayers. The investigated monolayers include octadecane, attached via hydrosilylation and hydrogermylation of 1-octadecene at Si and Ge surfaces, as well as para-substituted phenyl rings, attached by diazonium activation of hydrogenated Si and Ge surfaces. X-ray photoelectron spectroscopy of the modified Si and Ge surfaces, together with four- probe measurements of ultrathin (20-40 nm) silicon-on-insulator channels, functionalized with the monolayer structures, indicate that there is downward band bending, up to 200 meV, associated with assembling these organic monolayers on the semiconductor substrates. This band bending does not directly correlate with the dipole moment or electron withdrawing or donating character of the molecular moieties, pointing to the critical roles of the nature and quality of the self-assembled monolayer, and the intrinsic electronic structure of the semiconductor material in defining the interfacial electronic structure of the passivated Si and Ge surfaces.