Electrical characterization of metal-molecule-silicon junctions

Direct assembly of molecules onto silicon surfaces is of particular interest for potential employment in hybrid organic-semiconductor devices. In this study, aryl diazonium salts are used to assemble covalently bound molecular groups onto a hydride-passivated, oxide-free n-type Si(I 11) surface. The reaction of 4-(trimethylsilylethynyl)benzenediazonium tetrafluoroborate generates a molecular layer of 4-(trimethylsilylethynyl)phenylene (TMS-EP) on the Si surface. The monolayer modifies the electrical properties of the interface and exhibits nonlinear current-voltage characteristics, as compared with the ohmic behavior observed from metal-n(++)-Si(I 11) junctions. Results of current-voltage measurements at variable temperatures (from 300 to 10 K) on samples made with the TMS-EP molecules do not show significant thermally-activated transport, indicating tunneling is the dominant transport mechanism for this device structure. The measured data is compared to a tunneling model. (C) 2003 Elsevier Ltd. All rights reserved.