Nanoscale electromachining: Fundamental understanding and instrumentation enabling an electric discharge based nanoscale machining system

Nanotechnology is slowly making its way into mainstream of commercial production. However, nanoscale machining of non-silicon heterogeneous materials at room temperature and pressure was still a fairly elusive goal. Most nanoscale fabrication/machining processes require a high vacuum, highly controlled environments, and very specialized equipment among other stringent requirements for their proper functioning. The goal of the research presented in this dissertation was to develop a nanoscale machining process which could be performed at room temperature and pressure without the need for controlled environments. The applications for the process include correction of masks for lithography, machining of features in silicon nitride membranes for deoxyribonucleic acid (DNA) nucleotide analysis, in situ transmission electron microscopy (TEM) sample preparation, slicing of nanotubes and nanofibers and Z-axes interconnects for electronics.;Using such instrument configuration, machining of features as small as 8nm in hydrogen flame annealed atomically flat gold was demonstrated with tungsten and platinum-iridium tools operating in n-decane and commercially available EDM oils as a dielectric. Automatic software based control to machine arrays of features was added during the course of the research. A method for electrochemical etching of consistent nanoscale tools was developed. An in situ method based upon current-displacement spectroscopy was developed to analyze the tool quality. DC and pulse breakdown properties of liquid dielectrics were studied for the first time to develop Paschen curves for nanoscale gaps.;Across nanoscale gaps, the dielectric molecules were found to breakdown at an electric field two orders of magnitude greater than at the macroscale. The most likely reason for such an increase in the electric field was the nano-confinement of the molecules. TEM analysis of the tools revealed that even prior to nanoscale breakdown the tool surface was modified to a nanocrystalline matrix of tungsten oxide, tungsten, carbon in graphite form and amorphous carbon. Tungsten atom clusters were found to migrate from the tool apex prior to breakdown providing clues to tool wear at the nanoscale. The study of pulse breakdown across gaps 5nm and less revealed the effects of 'adsorption compression' leading to a delayed recovery (>8ms) of dielectric strength after breakdown. The recovery times were measured for the first time for increasing nanoscale gaps via the analysis of the current pulse. The recovery times were measured to first increase and then saturate to a value of 1.4ms, very similar to macro scale recovery times. It was expected that using nano-EM in pulse configuration one would be able to machine nanoscale features at a rate of 500Hz.;The nanoscale electro-machining (nano-EM) process brings together two technologies which have mostly developed independently. First was the technology of electric discharge machining (EDM) in which an electrical discharge occurs across two conductive materials separated by a distance of a few microns in a liquid dielectric to cause machining of both materials. The second was the technology of scanning probe microscopy (SPM) and in particular scanning tunneling microscopy (STM). In a STM, a sharp conductive tip scans over a conducting/semi-conducting surface to produce a three dimensional profile of the surface. Machining of surfaces with a STM has been explored quite extensively in the literature. This research distinguishes itself from others in the past by virtue of two innovations, first was the use of a dielectric between the STM tip and the sample and second was to separate the two by known distances to perform set up discharge at the nanoscale.