MS Thesis Presentation by David C. Beaulieu
Monday, April 11, 2005
(Dr. Jack Lackey, Chair)
"Electron Beam Chemical Vapor Deposition of Platinum and Carbon"
Electron Beam Chemical Vapor Deposition (EBCVD) is a technology that uses an electron beam to provide localized deposition for fabrication of nanoscale structures or devices. In this process, impinging electrons dissociate adsorbed precursor molecules, forming a deposit on the substrate. A focused electron beam, such as in an SEM or TEM, can be used to form structures with high aspect ratios. Reagent gas molecules typically come from an organometallic compound or a hydrocarbon. Primary electrons from the beam impact a substrate, causing secondary electrons to be emitted. These secondary electrons play a prominent role in dissociating the adsorbed reagent molecules. The deposition process depends on many factors including the precursor properties and the electron beam properties.
This thesis describes the use of a modified Scanning Electron Microscope (SEM) to fabricate platinum and carbon nanostructures and analysis of these structures with respect to growth rates, geometry, and microstructure. A gas injection system featuring a small diameter needle was used to deposit platinum from an organometallic compound. The Environmental mode of the microscope was used to deposit carbon from a methan/argon mixture. Columnar fiber deposits are made by leaving the beam in a fixed location, and line deposits are made by scanning the beam back and forth over a specified region. Process variables including voltage, beam current, and deposition time were controlled and manipulated in statistically designed experiments in order to study the effects on fiber deposition. Voltage, beam current, dwell time, and line time were varied to study the effects on line deposition. Emphasis was placed on optimizing the deposition rates for both line and fiber deposits. Geometric features such as aspect ratio were also investigated. Specimen geometry was observed via scanning electron microscopy, and deposit composition was determined by EDS and EELS.