A Field-Ion Microscope and 3-D Atom-Probe Microscopy Study of Tungsten Disulfide and Carbon Nanotubes,Public Deposited
Fullerene and inorganic fullerene-like nanotubes are molecules with the unique geometry of a single layer or multiple layers of a bulk material oriented in a tube. These molecules have novel mechanical properties and great potential in experimental systems for nanotechnology and nanodevices. The threedimensional atom-probe (3DAP) microscope is an atomic resolution microscope that can chemically identify specimens evaporated at high voltages. Specimens for the 3DAP are typically metals and must be prepared in a finely tapered tip for use in the 3DAP. This study applies the method of 3DAP microscopy to tungsten-disulfide and carbon nanotubes to investigate the chemical properties of the nanotubes and expand the functionality of the 3DAP microscope. Specimens of both tungsten-disulfide and carbon nanotubes, attached to metal filaments via conductive epoxy, were prepared for use in the 3DAP microscope. Atomic resolution micrographs of the tips of both nanotube specimens were collected using field-ion microscopy in the 3DAP microscope. These micrographs exhibited circular patterns indicative of the circular cross-section of the nanotube specimens. Also, multiple specimens of tungsten-disulfide nanotubes were evaporated and chemically identified using time-of-flight mass spectroscopy. Data were collected in the form of a mass spectrum of the detected ions. The tungsten-disulfide nanotubes evaporated as tungsten-sulfur complex ions. These experimental findings establish the technique of 3DAP microscopy for nanotubes and nonmetal materials.