9623355 Smith The ultimate goals of this research are to fabricate atomic- scale wires, perhaps even one atom in diameter, and to make low- temperature electrical measurements on them. The wires will be created by a combination of natural growth and patterning with the scanning tunneling microscope (STM). Early experiments will include imaging of a metal-chain- forming system not previously studied by STM and studies of chain stability. Intermediate-scale contact probes to bridge between the chains and macroscopic contacts will be made using either step-edge evaporation or STM chemical vapor deposition. Experiments in this phase will examine any disruptive effects of these intermediate-scale pads on the atomic chains, and also any problems with electrical contact between the pads and the chains. Once a sample is made, it will be transferred to a low-temperature stage within the same ultrahigh vacuum chamber, and its electrical properties will be measured. As a prelude to all the above experiments, a study of the effects of stray capacitance on single electron tunneling (SET) will be performed. %%% This basic research project will examine some of the apparent challenges in creating atomic-scale electronic circuits. Our ultimate goals are to make the simplest of all such circuits, an atomic-scale wire (perhaps even one atom in diameter), and to perform low-temperature electrical measurements on it to explore quantum mechanical effects. We will make the wire using a combination of natural ordering of metals on semiconductor substrates, patterning with the scanning tunneling microscope, and "step-edge evaporation", a technique which uses small steps in the substrate to create nanometer-scale structures. There are several apparent challenges . For most materials, it appears that the electrons needed for electrical conduction within the wire would be sucked away by the substrate on which the wires are created. The creation of electrical connections betw een the wires and the macroscopic world may disrupt the wires, or the wires might be disrupted by thermal fluctuations. Electrical contact between the wires and the macroscopic contacts may prove difficult. However, we are confident that each of these challenges can be met, and suggest several promising strategies. ***
