Advances in techniques for the nanoscale manipulation of matter are important for the realization of molecule-based miniature devices with new or advanced functions. A particularly promising approach that involves the construction of hybrid organic-molecule/ silicon devices requires detailed study of the electrical transport through molecules that are already bound to the substrate. This presents a twofold challenge: in the formation of nanostructures that will constitute the active parts of future devices, and in the construction of commensurately small connecting wires to interface with the outside systems. The performance of nanoscale devices will ultimately depend on the ability to control charge transport through atomic scale structures. However, simultaneous integration of the molecular wire to the substrate and to the conductive interconnects requires materials that are able to withstand the harsh chemical and thermal treatments, employed to produce atomically clean surfaces, and, at the same time still maintain their integrity as interconnects.
I will describe a novel method for interconnect fabrication, developed at NRC SIMS, that meets the stated requirements and is based on the unique properties of titanium disilicide (TiSi2) and give specific examples where it was successfully applied to study the transport properties of chemically modified semiconductor surfaces.
The described technique combined with proper lithographic contact pattern and simple modification of the STM sample stage allows in situ electronic transport measurement of chemically modified surfaces on a submicron scale. When complimented by the focused ion beam or electron beam lithography, it reaches into the nano scale range (<30nm), where testing of the validity of transport theory at the molecular level and addressing issues such as the dependence of conductivity on conformation becomes possible.