Thermal-field type electron source composed of transition metal carbide material with artificial facet
AssigneeApplied Physics Technologies, Inc.
InventorsWilliam A. Mackie, Gerald G. Magera
Life of this patent
Estimating the term…
Abstract
An electron source is made from mixed-metal carbide materials of high refractory nature. Producing field-enhanced thermionic emission, i.e., thermal-field or extended Schottky emission, from these materials entails the use of a certain low work function crystallographic direction, such as, for example, (100), (210), and (310). These materials do not naturally facet because of their refractory nature. The disclosed electron source made from transition metal carbide material is especially useful when installed in a scanning electron microscope (SEM) performing advanced imaging applications that require a high brightness, high beam current source.
Claims12
A source of thermal-enhanced field emission, comprising:
- a substrate in the form of a unitary article made of a transition metal carbide material of high refractory nature, the substrate having a tip of rounded end-form in a low work function crystallographic direction for on-axis, high brightness electron emission and characterized by geometrical invariance in response to one or both of temperature and field change, the tip of rounded end-form having a radius of curvature of between about 5 nm and about 500 nm.
A source of thermal-enhanced field emission, comprising:
- a transition metal carbide substrate of high refractory nature, the substrate having a tip of rounded end-form in a low work function crystallographic direction for on-axis, high brightness electron emission;
- characterized by geometrical invariance in response to one or both of temperature and field change;
- and, during operation, in response to application of a beam voltage, producing electron emission at angular intensity levels of greater than 10 mA/sr and to about 75 mA/sr.
Dependencies are inferred from the claim text.