Properties of electronic traps at silicon/1-octadecene interfaces

Abstract

Silicon surfaces with (111) orientation were hydrogenated in NH4F solution. Alkyl chain monolayers were self-assembled on the hydrogen-terminated silicon (Si–H) surface by the free-radical reaction of 1-octadecene and SiH, activated by ultraviolet (253.7 nm) illumination. Comprehensive electrical characterization of the metal/1-octadecene/silicon structures yielded experimental data on the (silicon–monolayer) interface trap parameters. The admittance data indicated the realization of a true silicon/organic-monolayer interface. The interface trap density obtained, for p-type silicon, was 1.7–3.0×1011/cm2 V over an energy range of 0.22–0.73 eV over the valence band edge. These interface trap densities can be considered remarkably low for a silicon interface formed around room temperature, and are an order of magnitude lower than what was obtained in the case of alkyl chain organic monolayers on naturally oxidized silicon surfaces. The interface trap density was found to be strongly influenced by the silicon doping type and density. This observation suggests that the position of the surface Fermi level has a strong influence on the quality of the octadecene–silicon interface.