Ultra high vacuum fabrication of metallic contacts for molecular devices on an insulating surface

The preparation and characterization of metallic wires on insulating substrates by a variety of mechanisms has been explored. A multi-scale approach utilizing microfabricated silicon stencil masks, feedback controlled electromigration, and field induced metal cluster deposition in a novel geometry has been explored on potassium bromide (KBr), indium phosphide (InP), and silicon oxide substrates in an ultra-high vacuum environment (UHV).;Metallic wires deposited using these stencils as well as electron beam lithography were electrically stressed and the breaking characteristics analyzed. Typical nanometer scale gaps were observed, as well as larger features more commonly found in the breaking of bamboo-like structures in gold wires 100 nm in size or less, particularly with a significant series resistance. These larger gaps are expected to be more applicable for the deposition of subsequent metallic clusters and preparation of molecular devices.;As a step towards connecting the initially deposited wires as well as localized molecules in an a fashion allowing atomic scale imaging by AFM, modelling and experiments of field induced deposition of gold clusters on KBr and InP substrates was carried out. Deposition on InP substrates with a backside 2D electron gas as a counter-electrode demonstrated the feability of this deposition technique in UHV. Subsequent depositions on or adjacent to metallic pads on the bulk insulating KBr provided a proof of principle of the technique, though some experimental limitations such as large current pulses with the tip in close proximity to the surface are discussed.;The initial deposition of gold, and tantalum wires between one hundred nanometers and micrometers in size was performed using reinforced silicon nanostencils. The stencil fabrication was discussed, and an examination of the deformation of the integrated structures under the deposition of highly stressed tantalum films was shown to be significantly smaller than typical structures.