Effect of Doping on Electronic Transport through Molecular Monolayer Junctions

Electron irradiation can alter electronic charge transport through Si−CH 2 (CH 2 ) 12 −CH 3 //Hg molecular junctions. Applying UPS, XPS, Auger, NEXAFS, and electrical transport measurements, we show that irradiation induces defects, most likely C C bonds and C−C cross-links, which introduce new electronic states into the HOMO−LUMO gap of the alkyl chains, and, hence, effectively dope these layers. We demonstrate a 1−2 order of magnitude enhancement in current, clearly distinguishable from that of defects in as-prepared layers.