Field-Assisted Diffusion of Copper Atoms

Through Electrostatic Self-Assembly Layers

David Purger

2004-2005

Abstract

Manipulation of small quantities of copper atoms is integral to the design of circuit components and other devices on the nanoscale. This is possible through field-assisted diffusion (FAD), in which a group of negatively charged atoms migrates towards a positively charged location on the surface. It was hypothesized that the additional presence of electrostatic self-assembly (ESA) films of ionically-bound bilayers will facilitate FAD of copper atoms by reducing the interatomic forces that resist atomic movement, allowing smaller groups of atoms to be manipulated. FAD with ESA treatment yielded more well-defined groups of copper atoms than did the control cases.

A scanning tunneling microscope (STM) was used to image a copper surface at room temperature and pressure and to deliver ten 1 volt pulses for .033 second to the surface, causing atoms to form groups and migrate towards the STM tip. On untreated surfaces, the probability of formation of a well-defined group of atoms was found to be 10.8% per voltage pulse delivered. Treatment with ESA bilayers, however, yielded a 15.7% chance of formation per voltage pulse.

ESA treatment markedly decreased the difficulty of creating and moving well-defined groups of copper atoms by field-assisted diffusion across a copper surface at room temperature and pressure. This method could potentially be applied to current nanotechnological procedures, such as building nanoscale circuitry and electron corrals, high-strength material construction, and chemical processing, to increase their efficiency and accuracy.